Computing Acronyms

Acronyms common in computing, hacker culture, and everyday software engineering conversations. This section collects concise definitions and quick examples to help you grok the jargon fast. A note about the legacy/historical subsections:

• Legacy: outdated but still in use.
• Historical: obsolete, mostly of historical interest.

Software Architecture

Acronym	Meaning	Example
C4	Context–Container–Component–Code — lightweight hierarchical diagramming model for communicating software architecture at multiple levels of abstraction.	Draw a system Context and Container diagram for a web app; break a service into Components; optionally add Code-level diagrams.
CQRS	Command Query Responsibility Segregation — separate writes/reads.	Write model emits events; read model is a projection.
ECS	Entity Component System — decompose game and simulation logic into data-only components processed by systems operating on matching entities.	Game engine with Position/Velocity components updated by a PhysicsSystem; rendering system consumes Mesh components.
EDA	Event-Driven Architecture — async event-based systems.	Publish domain events to Kafka; services react.
ES	Event Sourcing — persist state changes as an append‑only log of events and rebuild current state by replaying them.	Order aggregate applies OrderPlaced/ItemAdded events; projections update read models.
SOA	Service-Oriented Architecture — collaborating services.	Decompose monolith into services.
Legacy
COM	Component Object Model — Microsoft binary-interface standard for reusable components with reference counting and interface-based polymorphism.	Query IUnknown/IDispatch; register COM servers; Office automation via COM.
COM+	Component Services — evolution of COM/DCOM on Windows that adds declarative transactions, role-based security, queued components, and pooled object activation managed by the OS.	Configure COM+ applications in Component Services MMC; legacy enterprise apps use COM+ transactions and queued components before .NET.
DCOM	Distributed COM — extension of COM for inter-process and cross-machine communication using RPC.	Remote COM server activation/config over the network using DCOMCNFG.
DDE	Dynamic Data Exchange — legacy Windows message-based mechanism for applications to exchange data and commands via shared memory conversations; superseded by OLE/COM automation.	Early Windows apps used DDE for live spreadsheet/word processor links; replaced by OLE automation and modern IPC.
EJB	Enterprise JavaBeans — server-side component model for building distributed, transactional applications in Java; heavyweight and largely superseded by lighter frameworks.	Session Beans, Entity Beans, MDBs in a Java EE/Jakarta EE application server.
ESB	Enterprise Service Bus — centralized integration/message bus with mediation, routing, and governance typical of classic SOA; considered heavyweight today.	Hub‑and‑spoke integration; replaced by microservices and event streaming (Kafka).
MAPI	Messaging Application Programming Interface — Windows component API for email, calendaring, and messaging integration, primarily used by Microsoft Exchange/Outlook clients.	Outlook talks to Exchange via Extended MAPI; legacy apps used Simple MAPI to open/send mail through the default client.
MOM	Message-Oriented Middleware — infrastructure for asynchronous communication between distributed systems via messages and queues, decoupling producers and consumers.	IBM MQ, TIBCO, MSMQ; modern equivalents include Kafka and RabbitMQ.
MSMQ	Microsoft Message Queuing — durable asynchronous messaging middleware built into Windows that provides store-and-forward queues with transactional and secure delivery.	Legacy enterprise apps used MSMQ to decouple services; integrates with COM+, WCF, and bridge adapters for REST/HTTP.
OCX	OLE Control Extension — a legacy Microsoft standard for reusable software components based on COM/OLE, the predecessor to ActiveX controls.	Embedding third-party UI controls (.ocx files) in Visual Basic 6 applications.
SOAP	XML-based messaging protocol for web services.	Enterprise integrations over SOAP.
WCF	Windows Communication Foundation — a legacy .NET framework for building service-oriented applications.	Superseded by gRPC and ASP.NET Core Web API.
WF	Windows Workflow Foundation — a legacy .NET framework for building workflow-based applications.	State machine or sequential workflows in older .NET applications.
Historical
CORBA	Common Object Request Broker Architecture — OMG standard for language- and platform-neutral distributed objects communicating via an Object Request Broker.	Define interfaces in IDL; ORB uses IIOP for interop between stubs and skeletons.
DCE	Distributed Computing Environment — OSF framework for distributed applications providing RPC, security (Kerberos), directory, and threading services.	Build client/server apps with DCE RPC; secure with GSSAPI; use CDS for naming.

Software Design

Acronym	Meaning	Example
AoS	Array of Structs — contiguous collection where each element stores all fields, offering good spatial locality for per-entity operations.	struct Particle { float x, y, z; } particles[N]; iterate once to update position/velocity.
CPS	Continuation-Passing Style — express control flow by passing an explicit continuation function instead of returning normally.	f(x, k) calls k(result); enables tail calls, trampolines, async composition.
CSP	Communicating Sequential Processes — formal concurrency model where independent processes interact solely via message‑passing over channels (no shared memory).	Go channels/select and occam are CSP‑inspired; model systems as processes and rendezvous on channels.
DDD	Domain-Driven Design — model around the domain.	Ubiquitous language in code and docs.
DI	Dependency Injection — provide dependencies from the outside rather than creating them inside.	Pass a Logger to a service constructor instead of instantiating it.
DIP	Dependency Inversion Principle — depend on abstractions, not concretions.	Accept a Logger interface, not a concrete ConsoleLogger.
DRY	Don't Repeat Yourself — avoid duplicating knowledge in code and docs.	Extract a function instead of pasting the same block twice.
DTO	Data Transfer Object — simple data container.	Map entities to DTOs for API responses.
FRP	Functional Reactive Programming — model time‑varying values and event streams with functional operators.	UI state as RxJS Observables using map/merge/switchMap.
ISP	Interface Segregation Principle — prefer many small, client‑specific interfaces.	Use Readable/Writable instead of a bloated File interface.
KISS	Keep It Simple, Stupid — prefer simple solutions that meet requirements.	Use a plain function instead of a custom class hierarchy.
LSP	Liskov Substitution Principle — subtypes must be substitutable for their base.	A subclass shouldn't strengthen preconditions or weaken postconditions.
MVC	Model–View–Controller — separate data, presentation, and control flow.	Controllers orchestrate; Views render; Models hold domain data.
MVVM	Model–View–ViewModel — bind UI to a ViewModel that exposes state/actions.	Two-way binding in front-end frameworks.
OCP	Open/Closed Principle — open for extension, closed for modification.	Add a new strategy class instead of editing a switch.
SDI	Single-Document Interface — application model where each document is opened in its own separate top-level window.	Web browsers, VS Code; each window is an independent instance.
SoA	Struct of Arrays — layout that keeps each field in its own contiguous array to enable SIMD/vectorization and cache-friendly columnar processing.	Separate x[N], y[N], z[N] arrays for particles to update components with wide vector loads.
SoC	Separation of Concerns — isolate responsibilities into distinct modules.	Keep validation, business logic, and persistence in separate layers.
SOLID	Five OO design principles: SRP, OCP, LSP, ISP, DIP.	Extract interfaces and inject dependencies via constructors.
SRP	Single Responsibility Principle — one reason to change.	Split parsing and rendering into separate classes.
UML	Unified Modeling Language — notation to visualize/design systems.	Class and sequence diagrams for architecture and behavior.
WET	Write Everything Twice — tongue-in-cheek opposite of DRY.	Duplicate code rather than refactor.
WIMP	Windows, Icons, Menus, Pointer — classic graphical user interface paradigm built around overlapping windows, iconography, menu bars, and a pointing device.	Xerox Star and Apple Macintosh popularized WIMP desktops; modern desktop OSes retain the model.
YAGNI	You Aren't Gonna Need It — don't build features until necessary.	Skip a caching layer until profiling shows the need.
Legacy
MDI	Multiple-Document Interface — application model where multiple child windows are contained within a single parent window.	Classic desktop apps (early Photoshop/Office); child windows for each document.

Software Engineering

Acronym	Meaning	Example
BDD	Behavior-Driven Development — specify behavior in examples (Given/When/Then).	Feature files drive implementation and acceptance tests.
BDUF	Big Design Up Front — invest in upfront architecture/design before implementation.	Comprehensive UML/specs prior to coding (vs iterative/agile).
CD	Continuous Delivery/Deployment — automated release pipeline to ship safely.	Tagging main triggers a production deploy.
CI	Continuous Integration — frequently merge to main with automated tests.	Every PR runs unit and integration tests in CI.
CI/CD	Combined practice of Continuous Integration and Delivery/Deployment.	Build, test, artifact, deploy stages in one pipeline.
DSC	Desired State Configuration — declarative configuration management approach that defines the target state and lets tooling converge systems to it continually.	PowerShell DSC or Azure Automanage enforces web server configs by applying declarative manifests and reporting drift.
DX	Developer Experience — overall quality of tools, workflows, and docs that make developers productive and happy.	One‑command setup, fast feedback loops, clear errors, great CLIs.
E2E	End-to-End — tests or flows that cover the full user journey across systems and components.	Cypress/Playwright tests from UI through API to DB.
EOL	End Of Life — product/version no longer supported with fixes or updates; plan upgrades before EOL to remain secure and compliant.	Ubuntu 20.04 reaches EOL → migrate to 22.04 LTS.
GA	General Availability — broad production release status following beta/RC; officially supported.	Mark v1.0 as GA and enable default rollout.
HCI	Human-Computer Interaction — discipline focused on designing, evaluating, and implementing user interfaces and human-centered systems.	Usability studies, prototyping flows, accessibility reviews for a new feature.
I18N	Internationalization — design for multiple languages/locales.	Externalize strings; ICU formatting; locale-aware dates/numbers.
ICU	International Components for Unicode — a mature and widely used set of C/C++ and Java libraries for Unicode support, internationalization, and globalization.	Use ICU for collation, date/time formatting, and character set conversion.
KPI	Key Performance Indicator — metric tracking performance toward a goal.	Conversion rate, p95 latency, crash-free sessions.
L10N	Localization — adapt an internationalized product for a locale.	Translate resources; RTL layout; localized units/images.
LTS	Long-Term Support — release line maintained with security/critical fixes for an extended period.	Choose Node.js LTS for production; receive patches without feature churn.
MQ	Merge Queue — automation that sequences merges and runs required checks on up-to-date commits so main stays green.	GitHub/GitLab merge queue rebases the next PR onto main, runs CI, and auto-merges when green.
MVP	Minimum Viable Product — smallest thing to deliver value/learning.	Ship a CLI prototype before a full GUI.
OKR	Objectives and Key Results — align goals and track outcomes.	Company-level objectives with measurable KRs.
PoC	Proof of Concept — quick prototype to validate feasibility.	Spike code to test a new database driver.
PR	Pull Request — propose code change for review/merge.	Open a PR for CI checks and team review.
QA	Quality Assurance — practices to ensure product quality via process and testing.	Test plans, manual/exploratory testing, and sign-off before release.
RAD	Rapid Application Development — iterative, prototyping‑focused approach emphasizing quick delivery and user feedback over heavy upfront planning.	Build a working prototype with low‑code/4GL tools and iterate with users.
RC	Release Candidate — build believed to be release‑ready, pending final validation.	Ship RC to staging for UAT and smoke tests.
RFC	Request For Comments — proposal/spec for feedback before adoption.	RFC for a breaking API change.
SCM	Source Control Management — processes/tools for tracking changes to source code and related assets; often used interchangeably with VCS.	Git as an SCM; branching strategies, code reviews, and CI integration.
SDLC	Software Development Life Cycle — structured process for planning, designing, building, testing, deploying, and maintaining software.	Phases: requirements → design → implementation → testing → deployment → maintenance.
SWE	Software Engineer — practitioner who designs, builds, tests, and maintains software systems.	Full‑stack SWE implementing features, writing tests, and doing code reviews.
TDD	Test-Driven Development — write a failing test, pass it, refactor.	Red → Green → Refactor per behavior.
UAT	User Acceptance Testing — end users validate requirements.	Business stakeholders test before release.
UI	User Interface — the visual and interactive surface users operate.	Screens, components, and controls in web/mobile apps.
UX	User Experience — usability and satisfaction.	Research, UX writing, usability testing.
VCS	Version Control System — track changes to code and collaborate.	Git (branches, commits, PRs), Mercurial.
WIP	Work In Progress — items in progress; limit to improve flow.	Cap WIP per Kanban column.
XP	Extreme Programming — agile practices emphasizing feedback/simplicity.	Pair programming, CI, refactoring, and TDD.
Legacy
CVS	Concurrent Versions System — an early, influential client-server version control system that popularized features like branching and merging.	Superseded by Subversion (SVN) and later Git.
Historical
Y2K	Year 2000 problem — class of bugs related to storing years with two digits, causing issues with dates in and after the year 2000.	Remediation projects to expand date fields and fix date logic.

Web Development

Acronym	Meaning	Example
AJAX	Asynchronous JavaScript and XML — async HTTP from the browser.	Fetch data without full page reload.
ARIA	Accessible Rich Internet Applications — a W3C specification for making web content and applications more accessible to people with disabilities.	Use role="button" and aria-label to make a <div> accessible as a button.
ASGI	Asynchronous Server Gateway Interface — the modern, async-capable successor to WSGI for Python web applications.	Run a FastAPI or Django 3+ app with Uvicorn.
ASP.NET	Active Server Pages .NET — Microsoft's web application framework for building dynamic web sites and services with languages like C#.	Build web APIs and Razor Pages with ASP.NET Core.
CMS	Content Management System — application for creating, managing, and publishing website content, often with roles, workflows, and plugins; headless CMS expose content via APIs.	WordPress/Drupal; headless CMS like Contentful/Sanity.
CSR	Client-Side Rendering — render in the browser via JS.	React SPA renders views on the client.
CSS	Cascading Style Sheets — style language for HTML.	Tailwind/vanilla CSS styles pages.
DOM	Document Object Model — tree for HTML/XML.	document.querySelector() manipulates nodes.
ES	ECMAScript — JavaScript specification.	ES2023 features.
GraphQL	Query language/runtime for typed APIs.	Client requests specific fields only.
HTML	HyperText Markup Language — web markup.	<div>, <a>, <section> structure pages.
IIS	Internet Information Services — Microsoft's web server software for Windows.	Host ASP.NET applications on Windows Server with IIS.
JS	JavaScript — language of the web.	Frontend apps, Node.js scripts.
LTR	Left-To-Right — text direction where writing proceeds from left to right; default for Latin scripts.	HTML dir="ltr"; ensure proper bidi handling with Unicode markers where needed.
NPM	Node Package Manager — default package manager and registry client for Node.js, distributing JavaScript packages and managing project dependencies/scripts.	npm install react adds dependencies; package.json defines scripts run via npm run build.
OpenAPI	Standard to describe HTTP APIs (Swagger).	Generate clients from openapi.yaml.
PWA	Progressive Web App — offline/installable web app.	Add service worker and manifest.
REST	Representational State Transfer — resource APIs.	GET /posts/42 returns a Post.
RTL	Right-To-Left — text direction where writing proceeds from right to left; used by scripts like Arabic and Hebrew.	HTML dir="rtl"; use logical CSS properties (margin-inline-start) for bidi layouts.
SEO	Search Engine Optimization — improve visibility/traffic.	Add metadata; optimize content.
SPA	Single Page Application — dynamic single page.	React/Vue app with client routing.
SSR	Server-Side Rendering — render HTML on server.	Next.js SSR pages.
TS	TypeScript — typed superset of JavaScript that compiles to plain JS.	Add static types/interfaces; transpile with tsc or bundlers.
UA	User Agent — identifier string a client sends describing the software, version, and sometimes device/OS.	HTTP User-Agent header; spoof/rotate UA for testing/scraping.
URI	Uniform Resource Identifier — generic identifier for names/addresses of resources; includes URLs (locators) and URNs (names).	mailto:hello@example.com, urn:isbn:9780143127796, https://example.com/.
URL	Uniform Resource Locator — reference (address) to resources on a network using a scheme, host, and path.	https://example.com/docs/index.html.
URN	Uniform Resource Name — a URI that names a resource without specifying its location; persistent, location‑independent identifiers.	urn:isbn:9780143127796, urn:uuid:123e4567-e89b-12d3-a456-426614174000.
WASM	WebAssembly — portable fast binary format.	Run Rust/C++ in the browser.
WCAG	Web Content Accessibility Guidelines — the primary international standard for web accessibility, published by the W3C.	Aim for WCAG 2.1 AA compliance with sufficient color contrast and keyboard navigation.
WSGI	Web Server Gateway Interface — the standard interface between Python web applications and web servers.	Gunicorn/uWSGI running a Flask/Django app via a WSGI callable.
WWW	World Wide Web — system of interlinked hypertext documents and resources accessed via the internet using HTTP(S) and URLs.	Browse websites over HTTPS with a web browser.
Legacy
ASP	Active Server Pages — Microsoft's first server-side script engine for dynamically generated web pages; superseded by ASP.NET.	Classic ASP with VBScript (<% ... %>) on IIS.
CGI	Common Gateway Interface — standard for web servers to execute external programs and generate dynamic content.	Apache invoking a CGI script to render a page.
IE	Internet Explorer — Microsoft's legacy web browser, superseded by Edge.	IE11 compatibility mode; legacy intranet sites requiring ActiveX.
JSP	Jakarta Server Pages (JavaServer Pages) — a technology for creating dynamically generated web pages with Java code embedded in HTML.	.jsp files compiled into servlets on a Java application server.
WSDL	Web Services Description Language — an XML-based interface definition language for describing the functionality of a SOAP web service.	Generate a client proxy from a .wsdl file; ?wsdl endpoint on a SOAP service.
XHR	XMLHttpRequest — legacy browser API for making HTTP requests from JavaScript (superseded by fetch).	xhr.open('GET', '/api'); handle onreadystatechange.

Programming Languages

Acronym	Meaning	Example
PHP	PHP: Hypertext Preprocessor — a widely-used open source general-purpose scripting language that is especially suited for web development.	WordPress, Laravel, and Symfony are built with PHP.
VB.NET	Visual Basic .NET — the modern, object-oriented successor to classic VB, running on the .NET platform.	Build Windows Forms or ASP.NET applications with VB.NET.
VBA	Visual Basic for Applications — the scripting language for Microsoft Office, used for automation and macros.	Automate Excel reports with VBA macros in the VBE.
Legacy
APL	A Programming Language — an array-oriented language known for its concise syntax using a special character set.	Financial modeling and data manipulation with APL's vector and matrix operations.
AWK	Aho, Weinberger, and Kernighan — a domain-specific language for text processing, typically used for data extraction and reporting.	awk '{print $1}' file.txt to print the first column of a file.
BASIC	Beginner's All-purpose Symbolic Instruction Code — simple, interactive language designed for accessibility, popular on microcomputers.	10 PRINT "HELLO", 20 GOTO 10; Microsoft BASIC, Dartmouth BASIC.
COBOL	COmmon Business-Oriented Language — verbose, English-like language for business, finance, and administrative systems on mainframes.	IDENTIFICATION DIVISION., PERFORM ... UNTIL ...; legacy financial systems.
FORTRAN	FORmula TRANslation — pioneering compiled language for numeric and scientific computing.	DO loops, GOTO, COMMON blocks; used in HPC and scientific libraries.
LISP	LISt Processing — early, influential high-level language family based on lambda calculus, pioneering many FP concepts and featuring code-as-data (homoiconicity).	(defun factorial (n) ...) in Common Lisp/Scheme; Emacs Lisp.
ML	MetaLanguage — an influential family of functional programming languages known for its static type system, type inference, and algebraic data types.	Standard ML (SML) and OCaml are popular dialects; influenced F#, Rust, and Haskell.
PL/I	Programming Language One — an imperative language developed by IBM for scientific, engineering, and business applications, combining features from FORTRAN and COBOL.	Legacy applications on IBM mainframes (z/OS).
RPG	Report Program Generator — a high-level language for business applications, primarily on IBM i (AS/400) systems.	Business logic in fixed-format RPG IV on an IBM iSeries server.
SML	Standard ML — a popular dialect of the ML programming language, known for its formal definition and use in language research.	SML/NJ and MLton are common compilers; used in theorem provers.
VB	Visual Basic (Classic) — event-driven language and IDE for rapid application development on Windows before .NET.	VB6 applications with COM components and ADO database connections.
Historical
ALGOL	ALGOrithmic Language — influential early family of imperative languages that introduced block structure, lexical scope, and formal grammar definition (BNF).	ALGOL 60/68 influenced Pascal, C, and many other languages.

Programming

Acronym	Meaning	Example
AAA	Arrange–Act–Assert — unit testing pattern that structures tests into setup (arrange inputs/fixtures), execution (act), and verification (assert expected outcomes).	Arrange a service and mocks; Act by calling the method; Assert on result and interactions.
ADT	Abstract Data Type — specification of behavior independent of implementation.	Stack/queue ADTs with array- or list-based implementations.
ADT	Algebraic Data Type — composite types formed by sums (variants) and products (fields), enabling expressive, type-safe modeling.	Rust enums/Haskell data types; Option/Either in FP.
AIO	Asynchronous I/O — a form of I/O processing that permits other processing to continue before the transmission has finished.	Linux io_uring or Windows IOCP for high-performance servers.
API	Application Programming Interface — a defined surface for one piece of software to interact with another.	POSIX file APIs, a graphics library API, or an HTTP endpoint.
ASM	Assembly Language — low-level programming language with a strong correspondence between instructions and the machine's architecture.	Write syscall wrappers in ASM; optimize hot loops with SIMD intrinsics or inline assembly.
AVL	Adelson-Velsky and Landis tree — self‑balancing binary search tree that maintains height balance via rotations to ensure O(log n) search/insert/delete.	Implement an ordered map/set with AVL rotations (LL/LR/RL/RR).
BAR	Base Address Register — PCI/PCIe register that stores the base address and size of a device resource so the host can map memory-mapped I/O or port ranges into the system address space.	GPUs/network cards expose VRAM or control registers via BARs; "Resizable BAR" allows mapping full GPU memory on modern systems.
BCL	Base Class Library — the standard library of core types and functions in the .NET Framework and its successors.	Use types from System namespace like String, List<T>, and HttpClient.
BEAM	Bogdan's Erlang Abstract Machine — the virtual machine at the core of the Erlang and Elixir ecosystems, known for its concurrency and fault tolerance.	The BEAM VM powers highly concurrent systems like WhatsApp.
BFS	Breadth-First Search — graph/tree traversal that visits neighbors level by level using a queue; finds shortest paths in unweighted graphs.	Level-order traversal of a tree; BFS from a source to compute distances/parents.
BSP	Binary Space Partitioning — recursively subdivide space with hyperplanes (planes in 3D, lines in 2D) to organize geometry for visibility, rendering order, and collision queries.	Classic FPS engines (e.g., Quake) use BSP trees for visibility/culling and painter's algorithm ordering.
BST	Binary Search Tree — ordered binary tree supporting average O(log n) search/insert/delete when balanced; worst‑case O(n) if unbalanced.	Implement sets/maps; inorder traversal yields keys in sorted order.
CAS	Compare-And-Swap — atomic operation that updates a memory location only if it still equals an expected value; foundation for lock‑free algorithms.	CAS loop for a lock‑free stack push; beware the ABA problem.
CLI	Command-Line Interface — text-based commands.	git, kubectl, custom CLIs.
CLI	Common Language Infrastructure — the open specification (ECMA-335) for the .NET runtime environment.	The .NET CLR is an implementation of the CLI standard.
CLR	Common Language Runtime — .NET VM.	Runs C# assemblies.
CRUD	Create, Read, Update, Delete — basic data ops.	REST endpoints map to CRUD on users.
CUI	Character User Interface — text/character-based UI typically rendered in terminals with limited graphics; overlaps with TUI.	Installer wizards and ncurses-style menus in a terminal.
DAG	Directed Acyclic Graph — directed graph with no cycles; commonly used to model dependencies and enable topological ordering in compilers, build systems, and task scheduling.	Topologically sort to order compilation units; represent dependencies in build graphs or AST passes.
DFS	Depth-First Search — graph/tree traversal that explores as far as possible along each branch before backtracking; typically implemented with recursion or an explicit stack.	Topological sort, cycle detection, connected components, subtree times.
DSL	Domain-Specific Language — tailored language.	SQL, Regex, build DSLs.
EOF	End Of File — no more data to read.	Read returns EOF on file end.
FASM/MASM/NASM/TASM	Flat Assembler / Microsoft Macro Assembler / Netwide Assembler / Turbo Assembler — popular assemblers for the x86 architecture.	Writing bootloaders or optimizing code with x86 assembly.
FFI	Foreign Function Interface — mechanism to call functions across language/ABI boundaries.	Rust extern "C" to call C; Python ctypes/cffi bindings.
FIFO	First In, First Out — queue discipline.	Message queues processing order.
FP	Functional Programming — pure functions/immutability.	Map/filter/reduce pipelines.
FSM	Finite State Machine — computational model with a finite number of states and transitions driven by inputs/events.	UI workflows, protocol handlers, and parsers modeled as FSMs.
GADT	Generalized Algebraic Data Type — ADT whose constructors can refine the result type, enabling more precise typing and safer pattern matches.	Haskell/OCaml GADTs for typed ASTs; matching narrows types.
GC	Garbage Collection — automatic memory management.	JVM/CLR collectors free unused objects.
gRPC	High-performance RPC over HTTP/2 with Protobuf.	Define .proto; generate client/server stubs.
GUI	Graphical User Interface — visual interaction.	Desktop app windows, buttons.
I/O	Input/Output — transfer of data to/from a program and external systems or devices.	File I/O, network I/O; blocking vs non‑blocking/async I/O.
IDE	Integrated Development Environment — all-in-one dev app.	IntelliJ, VS Code (w/ extensions).
IDL	Interface Definition Language — specification language to describe interfaces and data types for generating cross-language bindings and IPC stubs.	Define COM interfaces in MIDL or CORBA IDL; generate proxies/stubs for RPC.
IIFE	Immediately Invoked Function Expression.	(function(){ })() in JS.
JDBC	Java Database Connectivity — DB API.	DriverManager.getConnection(...).
JDK	Java Development Kit — Java dev tools.	javac, jar.
JRE	Java Runtime Environment — run Java apps.	java -jar app.jar.
JVM	Java Virtual Machine — runs bytecode.	JVM-based languages (Kotlin, Scala).
LINQ	Language-Integrated Query — a .NET feature that adds native data querying capabilities to languages like C#.	Use LINQ to query collections, databases (via EF), and XML.
LRU	Least Recently Used — cache eviction policy that discards the least recently accessed items first.	LRU caches/maps in memory-constrained systems.
LSB	Least Significant Bit — the bit with the lowest positional value in a binary number (2^0); determines odd/even and is affected first by increment.	In 0b1011, the LSB is 1; little‑endian stores LSB byte first.
LSP	Language Server Protocol — standard JSON-RPC protocol between editors and language servers for code intelligence.	VS Code/Neovim language servers for hover, completion, diagnostics.
MSB	Most Significant Bit — the bit with the highest positional value; often used as the sign bit in signed integers.	In 0b1011, the MSB is 1; big‑endian stores MSB byte first.
MST	Minimum Spanning Tree — subset of edges that connects all vertices in a weighted, undirected graph with minimum total weight and no cycles.	Compute MST with Kruskal (sort edges + DSU) or Prim (priority queue).
NaN	Not a Number — IEEE 754 floating‑point special value representing undefined/invalid results; propagates through computations and is unordered (not equal to any value, including itself).	0.0/0.0 or sqrt(-1.0) produce NaN; NaN != NaN is true; use isnan() to test.
NOP	No Operation — instruction or operation that intentionally does nothing; used for timing, alignment, patching, or as a placeholder.	CPU NOP instruction; inserting a no‑op in pipelines or bytecode.
NPE	Null Pointer Exception — runtime error arising from dereferencing a null reference/pointer in languages with nullable references.	Java NullPointerException, C# NullReferenceException; avoid with null checks, Option/Optional, or null‑safety features.
ODBC	Open Database Connectivity — cross-platform C API and driver model for accessing relational databases.	Configure DSNs; apps connect via ODBC drivers to SQL Server/MySQL/Postgres.
OLE	Object Linking and Embedding — Microsoft technology (built on COM) for embedding and linking documents/objects between applications.	Embed an Excel sheet in a Word doc; OLE automation for Office apps.
OOM	Out Of Memory — condition where available memory is exhausted and allocations fail.	Linux OOM killer terminates processes; runtime throws OOM error.
OOP	Object-Oriented Programming — encapsulation/inheritance/polymorphism.	Classes, interfaces, virtual methods.
ORM	Object-Relational Mapping — map objects to relational tables.	ORM entities and repositories.
OTP	Open Telecom Platform — the standard library, design principles, and set of tools for building robust, concurrent systems in Erlang/Elixir.	gen_server and supervisor are key OTP behaviours.
PCRE	Perl Compatible Regular Expressions — regex libraries and syntax compatible with Perl's regex engine (PCRE/PCRE2).	grep -P, nginx, PHP use PCRE/PCRE2 for advanced regex features.
RAII	Resource Acquisition Is Initialization — lifetime control.	C++ locks released at scope end.
Regex	Regular Expression — declarative pattern syntax for matching, searching, and transforming strings; available in most languages and tooling with varying feature levels (POSIX, PCRE, etc.).	Use /^foo.*bar$/ to validate inputs; run `rg --ignore-case 'error
REPL	Read–Eval–Print Loop — interactive shell.	Python/Node REPL.
RPC	Remote Procedure Call — call functions on a service.	gRPC CreateUser method.
RPN	Reverse Polish Notation — postfix notation for arithmetic expressions that eliminates parentheses and associates operators with operands directly; naturally evaluated with a stack.	Evaluate 3 4 + 2 * with a stack; HP calculators and some compilers/VMs use RPN internally.
SDK	Software Development Kit — tools/libs for a platform.	AWS SDK for programmatic access.
SICP	Structure and Interpretation of Computer Programs — seminal MIT textbook that teaches computer science fundamentals through Scheme, abstraction, and metalinguistic evaluation.	Work through the SICP exercises, building interpreters and analyzers to internalize recursion, higher-order procedures, and data-driven design.
SUT	System Under Test — the specific component or boundary being exercised by a test, often isolated from collaborators via test doubles.	Unit test drives the SUT (a service class) while stubbing its repository and asserting outputs/interactions.
TLS	Thread-Local Storage — per-thread storage for data that gives each thread its own instance of a variable.	C/C++ thread_local/__thread, POSIX pthread_key_create; Rust thread_local!.
TUI	Text-based User Interface — terminal UI.	htop, ncurses apps.
UB	Undefined Behaviour — program operations for which the language standard imposes no requirements, allowing compilers to assume they never happen and enabling aggressive optimizations.	C/C++ out‑of‑bounds access, use‑after‑free, signed overflow; can lead to unpredictable results; use sanitizers to detect.
UTC	Coordinated Universal Time — global time standard.	Timestamps/logs in UTC.
UWP	Universal Windows Platform — a platform for creating apps that run across Windows devices.	Build a Windows Store app with UWP and XAML.
VBE	Visual Basic Editor — the integrated development environment for writing and editing VBA code within Microsoft Office.	Press Alt+F11 in Excel to open the VBE.
VS	Visual Studio — Microsoft's integrated development environment (IDE) for .NET and C++ development on Windows.	Develop, debug, and deploy applications with the Visual Studio IDE.
WPF	Windows Presentation Foundation — a UI framework for building Windows desktop applications with XAML.	Modern desktop apps with data binding and hardware acceleration.
WYSIWYG	What You See Is What You Get — direct-manipulation editor.	Rich text editors.
XAML	Extensible Application Markup Language — a declarative markup language used by Microsoft UI frameworks like WPF and UWP.	Define UI layouts and data bindings in .xaml files.
Historical {colspan=-3}
RMI	Remote Method Invocation — Java's distributed objects technology enabling method calls on remote JVMs via stubs/skeletons over JRMP (or IIOP for RMI‑IIOP).	Early Java distributed systems; largely supplanted by HTTP/REST, gRPC, and message queues.

Compilers

Acronym	Meaning	Example
ANTLR	ANother Tool for Language Recognition — a popular parser generator for reading, processing, executing, or translating structured text or binary files.	Generate a parser from a grammar file for a custom language.
AOT	Ahead-Of-Time compilation — compile before runtime.	Angular AOT compiles templates during build.
AST	Abstract Syntax Tree — structured tree representation of parsed source code used by compilers and tooling.	AST nodes for statements/expressions in parsers/linters.
BNF	Backus–Naur Form — notation for expressing context‑free grammars used to define programming language syntax.	Language specs define grammar productions in BNF or EBNF.
CFG	Context‑Free Grammar — formal grammar class used to define programming language syntax; typically expressed in BNF/EBNF and parsed by LL/LR/GLR/PEG parsers.	Write grammar productions; generate parsers with yacc/bison/ANTLR.
CFG	Control Flow Graph — directed graph of basic blocks and edges representing possible control transfers within a function/program; foundation for data‑flow analysis and many optimizations.	Build CFG to compute dominators/loops; enable DCE, SSA construction, and liveness.
CIL	Common Intermediate Language — the bytecode language for the .NET runtime (CLR), to which languages like C# and VB.NET compile.	ildasm to inspect the CIL of a .NET assembly; also known as MSIL.
CSE	Common Subexpression Elimination — remove repeated identical expressions by computing once and reusing the value within a region.	Within a block, compute x+y once and reuse; global variants extend across blocks.
DCE	Dead Code Elimination — remove code shown by analysis to have no effect on program outputs/side effects, improving size and performance.	Eliminate unused assignments/branches after liveness/constant propagation; -O2 passes in LLVM/GCC.
DFA	Data Flow Analysis — family of static analyses that compute facts about program variables/paths over a control flow graph using lattice/transfer functions (e.g., reaching definitions, liveness, constant propagation).	Run forward/backward analyses on a CFG; feed results to optimizations like DCE, CSE, and register allocation.
DFA	Deterministic Finite Automaton — finite-state machine with exactly one transition per symbol for each state; used in lexers/pattern matching.	Tokenizer state machine generated from regular languages.
DWARF	Debug With Arbitrary Record Format — standardized debugging information format for compiled programs (types, symbols, line tables, call frames) used across platforms.	GCC/Clang emit DWARF in ELF/Mach-O; inspect with readelf --debug-dump or llvm-dwarfdump; GDB/LLDB consume DWARF.
EBNF	Extended Backus–Naur Form — BNF with additional operators (repetition, optional, grouping) for more concise grammar specifications.	{ } repetition, [ ] optional; used in many language grammars and docs.
FAM	Flexible Array Member — language/ABI feature where a struct’s last field is a size‑unspecified array used to tail‑allocate variable‑length data; not counted in sizeof and requires custom allocation/copy logic.	In C (C99+): struct S{size_t n; int a[];}; allocate with malloc(sizeof(struct S)+n*sizeof(int)); a occupies trailing storage.
GCC	GNU Compiler Collection — suite of compilers for C/C++/Fortran and more.	gcc/g++ toolchains for building software.
GL	Graphics Library — SGI's proprietary immediate-mode 3D graphics API for IRIS workstations; precursor to the portable OpenGL standard.	Develop IRIS GL applications on SGI hardware; OpenGL later standardized much of the API for cross-platform use.
GLSL	OpenGL Shading Language — high-level C-like language for writing programmable shaders targeting OpenGL and Vulkan (via SPIR-V).	Write vertex/fragment/compute shaders compiled by drivers or offline to SPIR-V for Vulkan pipelines.
GVN	Global Value Numbering — discover semantically equivalent computations (beyond syntactic equality) to eliminate redundancies across the dominator tree.	Treat t=x; z=t+y as x+y; coalesce values through copies/φ nodes in SSA.
HLSL	High-Level Shading Language — Microsoft’s shader language for DirectX that compiles to DXIL/DXBC and can be cross-compiled to SPIR-V for Vulkan.	Author shaders in HLSL for Direct3D 11/12; use DXC/FXC or SPIRV-Cross for other runtimes.
HM	Hindley–Milner — a classical type inference algorithm that automatically deduces the types of expressions in some statically typed languages.	The basis for type inference in ML-family languages and Haskell.
IR	Intermediate Representation — compiler/transformation-friendly program form between source and machine code.	LLVM IR, SSA-based IRs used for optimization.
JIT	Just-In-Time compilation — runtime optimization.	HotSpot JIT compiles hot methods.
LICM	Loop-Invariant Code Motion — hoist computations whose operands don’t change within a loop to preheaders, and sink post‑loop where safe.	Move len(arr)/c*2 out of the loop body to reduce work.
LLVM	Low Level Virtual Machine — modular compiler toolchain and IR used by many languages.	Clang/LLVM backends, llc, opt, and LLVM IR.
LTO	Link Time Optimization — whole‑program optimization performed at link time across translation units, typically by linking IR/bitcode and running interprocedural passes.	-flto in Clang/GCC; enables cross‑TU inlining, DCE, devirtualization, ICF/WPO.
MLIR	Multi-Level Intermediate Representation — an extensible compiler infrastructure in LLVM that models programs across dialects to enable reusable transformations for domain-specific compilers and accelerators.	Use MLIR dialects (Linalg, GPU, Tensor) to lower ML programs toward LLVM IR or hardware-specific codegen.
NFA	Nondeterministic Finite Automaton — automaton model for regular languages allowing ε‑transitions and multiple possible next states; typically converted to an equivalent DFA for efficient matching.	Build NFA from regex via Thompson's construction; convert to DFA by subset construction for lexers.
NRVO	Named Return Value Optimization — compiler optimization that elides copies/moves by constructing a named local return object directly in the caller’s storage.	T f(){ T x; return x; } constructs x in the caller (C++); differs from RVO on unnamed temporaries.
OBJ	Object File — intermediate binary produced by compilers/assemblers containing machine code, data, relocation records, and symbol tables to be linked into executables or libraries.	Build foo.o/foo.obj then link with ld/link.exe; inspect with objdump, otool, or llvm-objdump.
PEG	Parsing Expression Grammar — recognition‑based grammar formalism with ordered (prioritized) choice and unlimited lookahead; often parsed via packrat parsing with memoization for linear time.	Define a PEG for a language and parse with PEG.js/pest/PEGTL; use ordered choice instead of ambiguous CFGs.
PRE	Partial Redundancy Elimination — inserts computations to make partially redundant expressions fully redundant, then removes duplicates (often via Lazy Code Motion/SSA-PRE).	If a+b happens on some paths and later unconditionally, place it optimally so all uses share one computed value.
RTTI	Run-Time Type Information — runtime facility to query an object's dynamic type and perform safe downcasts/instance checks in languages with polymorphism.	In C++, use dynamic_cast<Base*> and typeid; in Java/C#, use instanceof/is and reflection APIs.
RVO	Return Value Optimization — compiler optimization that elides copies/moves by constructing a returned temporary directly in the caller’s storage.	T f(){ return T(); } constructs the T in the caller; guaranteed in C++17 (copy elision rules).
SPIR-V	Standard Portable Intermediate Representation — Khronos binary intermediate language for GPU compute/graphics shaders used by Vulkan, OpenCL, and WebGPU toolchains.	Compile GLSL/HLSL to SPIR-V for Vulkan pipelines; emit SPIR-V from MLIR/LLVM for compute shaders.
SSA	Static Single Assignment — IR form where each variable is assigned exactly once, using φ (phi) functions at merge points; simplifies data‑flow analysis and optimization.	Convert to SSA to enable efficient DCE, copy propagation, and value numbering; SSA in LLVM IR.
TCO	Tail Call Optimization — reuse the current stack frame for a tail call to avoid stack growth and enable efficient tail recursion.	Compilers transform tail-recursive functions into loops; mandated in some languages (Scheme), optional in others.
UFCS	Uniform Function Call Syntax — language feature that allows calling free/extension functions with method-call syntax by implicitly passing the receiver as the first argument.	D/Scala/Rust desugar x.f(y) to f(x, y); extension methods in C#/Kotlin/Swift.

Operating Systems

Acronym	Meaning	Example
ABI	Application Binary Interface — low-level contract governing calling conventions, data layout, and linkage between compiled code and the OS/runtime.	x86‑64 System V ABI, Windows x64 ABI; stable FFI boundaries.
APK	Android Package Kit — archived bundle (ZIP with AndroidManifest.xml, resources, and compiled bytecode) used to distribute and install Android apps.	Build app-release.apk, sign it, and install with adb install or upload to Play.
ASLR	Address Space Layout Randomization — security technique that randomizes process address spaces (stack/heap/ASLR-enabled libs) to make memory corruption exploits less reliable.	cat /proc/sys/kernel/randomize_va_space; Windows system-wide ASLR.
BAT	Batch file — Windows Command Prompt script file executed by cmd.exe; commonly .bat or .cmd.	Automation scripts using built-ins like echo, set, if, for.
BSD	Berkeley Software Distribution — family of UNIX-like operating systems descended from research UNIX at UC Berkeley, known for its permissive license.	FreeBSD, OpenBSD, NetBSD used in servers and embedded systems.
BSS	Block Started by Symbol — segment for zero‑initialized or uninitialized static/global data that occupies memory at load/runtime but takes no space in the object file beyond metadata (size).	C static int buf[4096]; goes to .bss; reduces binary size versus storing zeros.
CMD	Windows Command Prompt — command-line interpreter (cmd.exe) for Windows providing batch scripting (.bat/.cmd) and built-in shell commands.	Run cmd.exe; use dir, copy, set and %PATH%; legacy scripts for automation.
COW	Copy-On-Write — share pages or objects until a write occurs, then copy to preserve isolation; reduces memory/IO and enables efficient forks/snapshots.	fork() shares pages COW; VM snapshots; filesystem COW in ZFS/Btrfs.
DLL	Dynamic-Link Library — shared library format on Windows loaded at runtime into a process address space.	foo.dll loaded via LoadLibrary; shared code/plugins.
DPC	Deferred Procedure Call — mechanism (notably in Windows) to queue a function for execution at a lower IRQL than the ISR that scheduled it, enabling faster interrupt handling.	A network driver's ISR queues a DPC to process incoming packets.
DSO	Dynamic Shared Object — generic term for a shared library (.so, .dll, .dylib) loaded at runtime and linked into a process's address space.	Use dlopen to load a DSO and dlsym to resolve symbols from it.
DYLIB	Dynamic Library — macOS shared library format loaded by the dynamic linker.	libfoo.dylib via dyld; install_name_tool/rpaths for relocation.
ELF	Executable and Linkable Format — standard binary format for executables, object files, and shared libraries on Unix-like systems.	Linux binaries with sections/segments; inspect with readelf/objdump.
EXE	Executable file — Windows program file using the Portable Executable (PE) format for executables and DLLs.	Launch .exe apps; inspect PE headers with dumpbin/objdump.
FS	File System — on-disk or logical structure and set of rules the OS uses to organize, store, and retrieve files/directories, including metadata and allocation.	ext4, NTFS, APFS, ZFS; mount/unmount volumes; permissions and journaling.
FUSE	Filesystem in Userspace — kernel interface to implement filesystems in user space processes.	Mount sshfs/rclone via FUSE; custom FS without kernel modules.
GDT	Global Descriptor Table — a core data structure in the x86 architecture that defines memory segments for the CPU.	Kernel setup of GDT for code/data segments in protected mode.
GNOME	GNU Network Object Model Environment — free, open‑source desktop environment for UNIX-like systems, part of the GNU Project.	Default desktop on many Linux distributions; GNOME Shell with Wayland/X11.
HAL	Hardware Abstraction Layer — OS layer that hides hardware specifics behind a uniform API so drivers/system code can run across platforms.	Windows HAL; OS kernels providing common driver interfaces across architectures.
IDT	Interrupt Descriptor Table — x86 data structure that associates interrupt vectors with the addresses of their interrupt service routines (ISRs).	OS populates the IDT to handle hardware interrupts and exceptions.
IFS	Installable File System — an API in an operating system that allows new file systems to be loaded dynamically.	Windows IFS for NTFS, FAT32, and third-party file systems; OS/2's IFS.
IPC	Inter-Process Communication — exchange/coordinate between processes.	Pipes, sockets, shared memory, signals.
ISR	Interrupt Service Routine — function invoked by the OS in response to an interrupt to handle the event and acknowledge the controller.	Keyboard ISR on IRQ1 reads scancode; timer ISR updates ticks and EOIs the APIC.
KDE	K Desktop Environment (now the KDE community and Plasma desktop) — free, open‑source desktop environment and software suite for UNIX-like systems.	KDE Plasma on Linux/BSD; highly configurable desktop with KWin and Qt apps.
L4	L4 microkernel family — influential second-generation microkernel design emphasizing minimality, high performance, and user-space servers.	seL4 (verified secure); Fiasco.OC; used in secure embedded systems and virtualization.
Mach-O	Mach Object — executable/object file format used by macOS/iOS for binaries and libraries.	Inspect with otool/lldb; libfoo.dylib and foo.app/Contents/MacOS/foo.
MSI	Microsoft Installer — an installer package file format and API for Windows.	.msi packages for installing software on Windows.
NDIS	Network Driver Interface Specification — a Microsoft API for network card drivers, forming a layer between the protocol stack and the hardware driver.	Writing an NDIS miniport driver; the standard for Windows network drivers.
NTFS	New Technology File System — Windows journaling filesystem with ACLs, alternate data streams, compression, and quotas.	Format a Windows system volume as NTFS; set ACLs with icacls.
OS	Operating System — system software that manages hardware resources and provides common services for programs.	Linux, Windows, macOS; kernel, drivers, processes, filesystems.
PCB	Process Control Block — kernel data structure containing the state of a process (registers, PID, scheduling info, memory maps).	The OS saves/restores the PCB during a context switch.
PE	Portable Executable — Windows binary format for executables, DLLs, and object files.	Inspect with dumpbin/objdump; sections, import/export tables.
PID	Process Identifier — numeric ID assigned by the kernel to a process.	pid=1 init/systemd; ps -o pid,comm.
POSIX	Portable OS Interface — Unix-like standard APIs.	fork, exec, pthread APIs.
PTY	Pseudo Terminal — virtual terminal pair (master/slave) used by terminal emulators and remote sessions to emulate a real TTY.	/dev/pts/*, ssh -t, forkpty, tmux.
QNX	QNX Neutrino RTOS — commercial Unix-like real-time operating system with a microkernel architecture, widely used in embedded systems.	Automotive infotainment (BlackBerry IVY), industrial controllers, medical devices.
RCU	Read-Copy-Update — synchronization mechanism allowing lock-free reads by deferring updates/reclamation until all readers in a grace period complete.	Linux kernel uses RCU for highly concurrent data structures in networking/VFS.
RPM	RPM Package Manager (originally Red Hat Package Manager) — a package management system used by many Linux distributions.	rpm -i package.rpm; yum/dnf use RPM packages.
RTOS	Real-Time Operating System — OS designed for deterministic response and bounded latency, with priority-based scheduling and real-time primitives.	FreeRTOS, Zephyr, VxWorks on microcontrollers/embedded systems; hard vs soft real-time.
SO	Shared Object — Unix/Linux shared library format loaded by the dynamic linker.	libfoo.so via ld.so/dlopen; sonames and rpaths.
SUS	Single UNIX Specification — standard defining UNIX interfaces and behavior maintained by The Open Group, ensuring POSIX compliance and application portability.	SUS/POSIX APIs (unistd.h, signals, threads); conformant systems like AIX, HP-UX, macOS.
TCB	Thread Control Block — kernel data structure that stores the state of a thread, including its registers, stack pointer, and scheduling information.	Analogous to a PCB but for a thread; managed by the scheduler.
TID	Thread Identifier — numeric ID for a thread (often equals PID for single-threaded processes; Linux has per-thread TIDs).	gettid() on Linux; pthread_self() maps to a TID.
TPF	Transaction Processing Facility — IBM's high-performance successor to ACP, optimized for nonstop, large-scale transaction processing on mainframes in aviation, finance, and hospitality.	Airlines, card networks, and hotels run IBM ZTPF/TPF on IBM Z to process reservations and payments at extreme throughput.
TTY	Teletype/Terminal — character device for text I/O; terminal sessions.	/dev/tty, PTY in shells.
Legacy
AIX	IBM's UNIX (Advanced Interactive eXecutive) for POWER systems, featuring LPARs, SMIT, JFS2, and enterprise tooling.	IBM Power Systems running AIX on POWER9/POWER10; manage with SMIT/VIOS.
COM	DOS executable — simple flat binary loaded at offset 0x100 with ~64KB segment limit and no header.	Classic .COM utilities/programs on MS‑DOS/PC‑DOS; tiny loaders/stubs.
IVT	Interrupt Vector Table — x86 real‑mode table at 0x0000:0000 with 256 interrupt pointers; superseded by IDT in protected/long mode.	Bootloaders may patch IVT entries before switching modes.
JCL	Job Control Language — scripting language used on IBM mainframes to control batch job execution.	//SYSIN DD * statements in a JCL deck to submit a batch job.
MCP	Master Control Program — Unisys mainframe OS in the Burroughs large‑systems line, featuring a stack machine architecture and strong language support; still in use but niche.	Unisys ClearPath MCP systems (Burroughs B5000 lineage) running enterprise workloads.
NT	New Technology — Microsoft’s NT family/architecture underlying Windows NT and its successors (2000/XP/Vista/7/8/10/11), featuring a hybrid kernel, HAL, NTFS, and Win32/NT native subsystems.	Windows NT lineage; ver shows NT versioning; services/session model and security based on NT architecture.
UAC	User Account Control — Windows elevation and consent mechanism to limit silent privilege escalation.	Admin tasks prompt for consent; split‑token admin accounts.
UDS	Unix Domain Socket — IPC mechanism using socket endpoints on the local host with filesystem pathnames or abstract namespace.	/var/run/docker.sock; faster than TCP on localhost.
VDSO	virtual Dynamic Shared Object — small shared library exposed by the kernel and mapped into user processes to provide fast, syscall-free access to certain kernel routines.	gettimeofday() calls on Linux are often implemented via the vDSO to avoid context switches.
VFAT	Virtual FAT — an extension to the FAT filesystem that introduced long filename support in Windows 95.	Enabled filenames longer than the 8.3 DOS convention.
VFS	Virtual File System — OS abstraction layer that provides a uniform API over different filesystems and devices.	Linux VFS layer exposes common inode/dentry APIs across ext4, XFS, NFS, FUSE.
VM	Virtual Memory — OS abstraction that gives processes isolated address spaces mapped to physical memory via paging/segmentation.	Per‑process address spaces, page tables, demand paging, copy‑on‑write.
X11	X Window System (Version 11) — network‑transparent windowing system and protocol for bitmap displays on UNIX‑like systems.	Xorg/XWayland on Linux; XQuartz on macOS; ssh -X X11 forwarding.
z/OS	IBM's mainframe operating system for IBM Z, successor to OS/390 and MVS; provides JES2/3, RACF security, JCL batch, and UNIX System Services (POSIX environment).	Enterprise workloads on IBM Z mainframes; partitioned datasets, CICS/IMS, and USS shells.
ZFS	Zettabyte File System — advanced filesystem/volume manager with snapshots, checksums, compression, and COW semantics.	Create ZFS datasets/pools; instant snapshots/zfs send replication.
Historical
A/UX	Apple UNIX — Apple's early implementation of Unix for their 68k-based Macintosh computers, featuring a Mac-like GUI.	An early attempt to merge the Mac GUI with a POSIX-compliant Unix kernel.
ACP	Airline Control Program — IBM's specialized high-throughput transaction processing operating system for System/360 and System/370, engineered for airline reservations and other real-time industries; predecessor to TPF.	Run on IBM mainframes to power reservation systems; later evolved into the Transaction Processing Facility (TPF).
CDE	Common Desktop Environment — classic UNIX desktop environment based on Motif and the X Window System; widely used on commercial UNIX workstations in the 1990s.	HP‑UX, Solaris, AIX shipped CDE as the default desktop; superseded by GNOME/KDE.
COFF	Common Object File Format — early, influential format for executables and object files on Unix-like systems.	Predecessor to ELF and PE; used in early System V.
CP/CMS	Control Program / Cambridge Monitor System — IBM's experimental virtualization-focused time-sharing system for the System/360 Model 67, pairing a hypervisor (CP) with per-user CMS interactive environments.	Demonstrated full virtual machines hosting guest OSes; evolved into VM/370 and laid the groundwork for modern IBM mainframe virtualization.
CP/M	Control Program for Microcomputers — early microcomputer OS preceding MS‑DOS.	1970s/80s 8‑bit systems running CP/M.
CTSS	Compatible Time-Sharing System — pioneering time-sharing OS developed at MIT for the IBM 7090/7094; introduced concepts like password logins and interactive command shells; precursor to MULTICS.	MIT Project MAC on IBM 7094; early 1960s interactive computing.
DG/UX	Data General's UNIX for AViiON servers/workstations; SVR4-based, multi-processor support; discontinued.	DG AViiON systems running DG/UX; enterprise UNIX of the 1990s.
DOS	Disk Operating System — family of disk‑based OSes.	MS‑DOS, PC‑DOS, DR‑DOS.
DTSS	Dartmouth Time-Sharing System — early time-sharing operating system co-developed with the Dartmouth BASIC language to provide interactive computing access to students and faculty.	Students logged into DTSS terminals to run BASIC programs; influenced later educational and commercial time-sharing services.
EMS	Expanded Memory Specification — paged memory technique (bank switching) to access >1MB of RAM on 8086/286 PCs in real mode via a 64KB page frame in the UMA.	Lotus/Intel/Microsoft (LIM) EMS; configure with EMM386.EXE for DOS games/apps.
GCOS	General Comprehensive Operating System — Honeywell/Bull mainframe OS originally launched as GECOS (General Electric Comprehensive Operating Supervisor), known for robust batch and transaction processing.	Unix /etc/passwd "gecos" field traces back to GCOS interoperability; enterprises still run GCOS on Bull mainframes.
GEM	Graphics Environment Manager — a WIMP-style GUI from Digital Research, used on the Atari ST and Amstrad PCs.	The GEM desktop environment; competitor to early Mac OS and Windows.
GEOS	Graphic Environment Operating System — a GUI-based operating system for 8-bit home computers and later for PCs.	Popular on the Commodore 64; PC/GEOS was an alternative to early Windows.
HMA	High Memory Area — the first ~64KB of extended memory, made accessible in real mode on 286+ CPUs by manipulating the A20 line.	Load DOS into the HMA (DOS=HIGH) to free up conventional memory.
IRIX	SGI's UNIX for MIPS workstations/servers; renowned for graphics and the original home of XFS; discontinued.	SGI Octane/Onyx systems running IRIX; MIPSpro toolchain; legacy SGI graphics stacks.
ITS	Incompatible Timesharing System — MIT's hacker-centric time-sharing OS for the PDP-6 and PDP-10 that introduced extensible systems, open access, and influential developer culture.	Hackers ran ITS on MIT AI Lab PDP-10s; today enthusiasts explore it via SIMH/KA/KI/KL emulators.
LM	LAN Manager — a network operating system (NOS) developed by Microsoft and 3Com, a predecessor to Windows NT Server.	Competed with Novell NetWare; ran on OS/2.
MFT	Multiprogramming with a Fixed number of Tasks — an early configuration of IBM's OS/360 that managed a fixed number of concurrent jobs in static memory partitions.	One of the primary OS/360 options alongside MVT (Variable number of Tasks).
MP/M	Multiprogramming Monitor for Microprocessors — a multi-user version of the CP/M operating system.	Early 8-bit multi-user business systems; predecessor to Concurrent CP/M.
MULTICS	Multiplexed Information and Computing Service — ambitious time-sharing OS jointly developed by MIT, Bell Labs, and GE, pioneering concepts like hierarchical file systems, ring-based security, and dynamic linking.	Ran on GE-645/Honeywell machines; inspired UNIX and modern OS designs; notable for shared memory segments and user ring protection.
MULTICS	Multiplexed Information and Computing Service — influential time‑sharing OS from MIT/GE/Bell Labs that inspired many UNIX concepts.	1960s/70s mainframes; security and modular design influenced Unix.
MVS	Multiple Virtual Storage — mainstream IBM mainframe OS from the System/370 era onward, providing robust batch and transaction processing; evolved into OS/390 and z/OS.	Run CICS/IMS transactions; submit JCL batch jobs; manage DASD with VSAM.
MVT	Multiprogramming with a Variable number of Tasks — a configuration of IBM's OS/360 that was a precursor to MVS, allowing for a dynamic number of concurrent jobs.	One of the primary OS/360 options alongside MFT (Fixed number of Tasks).
NLM	NetWare Loadable Module — a server module (driver, application, or utility) that could be dynamically loaded and unloaded in the Novell NetWare operating system.	.NLM files for drivers and server applications on a NetWare server.
OS/2	IBM/Microsoft then IBM OS succeeding DOS.	OS/2 Warp on 1990s PCs.
OS/360	Operating System/360 — IBM's influential mainframe OS for the System/360, introducing concepts like JCL, partitioned datasets, and a family of compatible systems.	Run batch jobs with JCL; manage datasets on DASD; MFT/MVT variants.
OS/370	Operating System/370 — successor to OS/360 for System/370 mainframes, introducing virtual memory (SVS/MVS).	MVS (Multiple Virtual Storage) became the mainstream OS/370 version.
OS/390	Successor to MVS/ESA, integrating UNIX services (USS) and other modern features into the core mainframe OS; predecessor to z/OS.	Run UNIX and batch workloads on the same system; prepare for Y2K.
OSF/1	Open Software Foundation's UNIX, later Digital UNIX/Tru64; SVR4-based with Mach kernel components and advanced features.	DEC Alpha systems running Digital UNIX; TruCluster high-availability.
PLATO	Programmed Logic for Automatic Teaching Operations — pioneering computer-based education system with touch-enabled terminals, graphical courseware, and early online community features (forums, chat).	University of Illinois' PLATO IV terminals delivered interactive lessons and multiplayer games; influenced modern e-learning and social computing.
RISC OS	Acorn's desktop operating system for ARM-based Archimedes and Risc PC machines, featuring a WIMP interface and cooperative multitasking.	Run on Acorn Archimedes/Risc PC systems; modern builds run RISC OS Open on Raspberry Pi.
RSTS	Resource Sharing Time-Sharing — DEC's multi-user PDP-11 operating system that merged RT-11 friendliness with RSX services for schools and business computing.	Boot RSTS/E on a PDP-11 or under SIMH to run BASIC, COBOL, and timeshared workloads.
RSX	Real-Time System Executive — DEC's multi-user, multitasking real-time operating system family for PDP-11 minicomputers.	Run RSX-11M/RSX-11M-Plus on PDP-11 hardware or via SIMH for industrial control and retrocomputing.
RT-11	Real-Time 11 — DEC's single-user real-time operating system for PDP-11 minicomputers, optimized for lab automation and embedded control.	Load RT-11 from floppy/disk on PDP-11 hardware or run under SIMH for vintage development.
SABRE	Semi-Automated Business Research Environment — American Airlines/IBM's pioneering real-time airline reservation system derived from SAGE concepts.	Early 1960s SABRE mainframes booked flights via networked agent terminals; evolved into modern Sabre GDS platforms.
SAGE	Semi-Automatic Ground Environment — Cold War-era air defense system combining massive AN/FSQ-7 computers, radar feeds, and real-time command software to track aircraft and coordinate intercepts.	1950s USAF direction centers ran SAGE consoles and radar plots; preserved today via simulations and museum restorations.
SVR4	System V Release 4 — AT&T/Sun UNIX unifying System V, BSD, and Xenix features; foundation for many 1990s commercial UNIXes.	Solaris 2.x and UnixWare derive from SVR4 with STREAMS networking and SVR4 package tools.
TENEX	TEN Executive — BBN's influential PDP-10 time-sharing operating system introducing demand paging, virtual memory, and ARPANET innovations that fed directly into DEC's TOPS-20.	Early ARPANET nodes ran TENEX; features like the Exec shell, JSYS calls, and paging hardware shaped later TOPS-20 and other networked OSes.
TOPS	Total Operating System — DEC's time-sharing operating systems for the PDP-10/DECsystem-10 (TOPS-10) and DECsystem-20 (TOPS-20), foundational during the ARPANET era.	Explore TOPS-10/TOPS-20 on emulated DECsystem hardware; develop with ITS-style monitors and early networking tools.
TSR	Terminate and Stay Resident — DOS resident utility/program.	Keyboard macros/clock TSRs in MS-DOS.
TSS/360	Time Sharing System/360 — IBM's ambitious but troubled time-sharing operating system for the System/360 Model 67, introducing virtual memory and interactive access; lessons informed later VM/370.	Provided remote terminal access on S/360-67 with DAT hardware; performance/complexity issues led IBM to focus on successor systems.
UMA	Upper Memory Area — the memory block between 640KB and 1MB on PCs, used for system BIOS, option ROMs, and video memory; free portions (UMBs) could map drivers/TSRs.	Load drivers high with DEVICEHIGH in CONFIG.SYS to free conventional memory.
VAXELN	VAX Embedded Local Network — DEC's real-time operating system for VAX systems that provided networked, event-driven control applications with VMS tooling.	Build VAXELN images on VMS hosts and deploy to VAX hardware or emulators for industrial automation use cases.
VM/370	Virtual Machine/370 — IBM's first official release of the VM hypervisor for the System/370, a landmark in virtualization.	Predecessor to later VM/ESA and z/VM systems.
VM/CMS	Virtual Machine / Conversational Monitor System — the combination of the VM hypervisor and its single-user interactive CMS operating system.	The primary user experience on IBM mainframe time-sharing systems.
VMS	Virtual Memory System — DEC's operating system for VAX (later Alpha/Itanium as OpenVMS), featuring robust clustering and security.	VAX/VMS in enterprises; OpenVMS clusters with RMS/DCL.
WAITS	Stanford's timesharing system — derived from SAIL's modifications to DEC's TOPS-10 for PDP-10s, adding advanced editing, graphics, and music tooling that influenced interactive computing.	Hosted SAIL's AI research tools, graphical displays, and early computer music systems; many WAITS ideas migrated back into TOPS-10/TOPS-20 ecosystems.
WfW	Windows for Workgroups — an early version of Microsoft Windows that integrated peer-to-peer networking directly into the OS.	Windows 3.11 for Workgroups with File and Print Sharing.
XMS	Extended Memory Specification — standard for DOS programs to access extended memory (>1MB) on 286+ CPUs via a driver (HIMEM.SYS) and A20 gate control.	Load DOS high (DOS=HIGH); use XMS for RAM disks and apps needing large buffers.

Document Markup

Acronym	Meaning	Example
LaTeX	Document preparation system built on TeX that provides high‑level markup for typesetting complex documents (sections, figures, bibliographies) with excellent math support.	Write papers/books with LaTeX classes/packages; pdflatex/xelatex build pipelines.
MD	Markdown — lightweight plain‑text markup language for formatting documents with simple syntax for headings, lists, emphasis, links, and code.	README.md, GitHub Flavored Markdown; code fences and tables in docs/blogs.
RST	reStructuredText — plaintext markup language used in the Python ecosystem and Sphinx documentation generator; emphasizes readable source and structured directives.	Sphinx .rst docs with directives/roles; PyPI/ReadTheDocs project documentation.
TeX	Low‑level typesetting system designed by Donald Knuth providing precise control over layout and mathematics; foundation for LaTeX and many formats.	Typeset math-heavy documents; plain TeX macros; outputs DVI/PDF via engines like pdfTeX/XeTeX/LuaTeX.
XML	Extensible Markup Language — verbose structured data.	XML configs, SOAP payloads.
XSLT	Extensible Stylesheet Language Transformations — declarative language for transforming XML documents using template rules, XPath selection, and functions.	Transform DocBook/XML to HTML/PDF with Saxon/Xalan; XSLT 1.0/2.0/3.0.
Legacy
DTD	Document Type Definition — schema language defining the legal structure/elements/attributes of SGML/XML documents.	Validate XML with a DTD; <!DOCTYPE ...> declarations; legacy vs XML Schema/Relax NG.
XSD	XML Schema Definition — the W3C standard for defining the structure and data types of XML documents; the powerful successor to DTD.	Validate XML against an .xsd schema; generate code from schemas.
Historical
SGML	Standard Generalized Markup Language — meta-language for defining markup languages; foundation for HTML/XML; rarely used directly today.	SGML-based HTML 2.0/3.2 era; modern stacks use XML/HTML5 instead.

File Formats

Acronym	Meaning	Example
AAC	Advanced Audio Coding — a lossy audio compression format that is the successor to MP3, offering better quality at similar bitrates.	Standard audio format for YouTube, Apple devices, and digital video broadcasting.
CAB	Cabinet archive — Microsoft compressed archive format that supports embedded digital signatures and is commonly used to bundle Windows drivers, updates, and setup payloads.	Windows Update distributions and driver packages ship .cab files; expand or DISM extracts them.
CHM	Compiled HTML Help — Microsoft compressed archive format packaging HTML, images, and navigation for offline help files, typically viewed via the WinHelp system.	Windows applications shipped .chm manuals; hh.exe opens them; security hardening blocks untrusted CHMs.
DVI	Device Independent file format — TeX's output format describing pages and typeset content in a device‑agnostic way, later converted to PostScript/PDF or displayed via drivers.	Generate .dvi from TeX; view/convert with dvips, dvipdfmx, or viewers like xdvi.
EPUB	Electronic Publication — a popular open standard for e-books, using web technologies like HTML, CSS, and SVG.	Read .epub files on an e-reader or with a software viewer.
ICO	Icon file format — container for one or more images in various sizes/color depths, used for favicons and application icons.	favicon.ico in the web root; Windows .exe icon resources.
INF	Setup Information file — plain-text configuration scripts that drive Windows installation and configuration of drivers, services, and components.	Windows driver packages ship .inf files consumed by SetupAPI; pnputil adds or stages them.
INI	Initialization file — simple key/value configuration format organized into sections for Windows applications and many cross-platform tools.	.ini files under %WINDIR% or alongside apps; parsed by GetPrivateProfileString/config libraries.
MSI	Microsoft Installer package — database-backed installation package format used by Windows Installer to deploy applications, updates, and patches.	Enterprise software ships .msi packages; msiexec installs/uninstalls with logging and transforms.
OTF	OpenType Font — cross-platform font format that can contain PostScript or TrueType outlines and supports advanced typographic features.	.otf fonts for professional typography; supersedes PostScript Type 1.
PNG	Portable Network Graphics — lossless raster image format with DEFLATE compression, alpha transparency, and gamma/metadata support.	.png UI assets/screenshots; better compression than BMP; supports transparency.
PS	PostScript — page description language and programming language used primarily in desktop publishing and printing workflows.	Generate vector/print-ready .ps files; printers interpret PostScript directly; PDF evolved from it.
SVG	Scalable Vector Graphics — XML-based vector image format for resolution-independent graphics.	Inline icons/diagrams in HTML; CSS/SMIL animations.
TOML	Tom's Obvious, Minimal Language — minimal configuration format with clear semantics.	pyproject.toml, Cargo.toml tool configs.
TTF	TrueType Font — outline font format using quadratic Bézier curves; widely supported across operating systems and browsers.	.ttf fonts for desktop/web (often inside .ttc collections or wrapped as WOFF/WOFF2 for the web).
WOFF	Web Open Font Format — compressed container format for web fonts (TrueType/OpenType), enabling faster delivery; WOFF2 offers improved compression.	Serve .woff2 with a .woff fallback for modern web typography.
YAML	Human-friendly serialization format.	docker-compose.yml files.
Legacy
BMP	Bitmap Image File — raster image format (Device‑Independent Bitmap) storing pixel data with optional RLE compression.	.bmp screenshots/icons; large files compared to PNG/JPEG.
GIF	Graphics Interchange Format — legacy lossless raster image format limited to 256 colors, best known for supporting simple animations.	Animated memes; superseded by PNG for static images and APNG/video for complex animations.
MP3	MPEG-1 Audio Layer III — a popular lossy audio compression format that revolutionized digital music.	.mp3 files for music; superseded by AAC but still widely used.
RTF	Rich Text Format — plain-text document format with markup (control words and groups) for character/paragraph styling; widely supported across editors.	Save/export .rtf from word processors to interchange formatted text.

Data Encodings

Acronym	Meaning	Example
ASCII	American Standard Code for Information Interchange — 7‑bit character encoding defining codes 0–127; subset of UTF‑8.	Plain ASCII text files; printable characters and control codes.
BOM	Byte Order Mark — optional Unicode signature at the start of a text stream indicating endianness/encoding (UTF‑8/UTF‑16/UTF‑32).	Avoid UTF‑8 BOM in Unix scripts; UTF‑16 LE files start with FE FF.
CRLF	Carriage Return + Line Feed — sequence \r\n used by Windows and many network protocols as a line terminator.	HTTP headers and CSV on Windows use CRLF line endings.
DER	Distinguished Encoding Rules — binary ASN.1 encoding used for certificates/keys.	.cer/.der X.509 certs; binary form of ASN.1 structures.
EBCDIC	Extended Binary Coded Decimal Interchange Code — 8‑bit character encoding used primarily on IBM mainframes; incompatible with ASCII.	Converting EBCDIC files to ASCII/UTF‑8 when integrating with mainframe systems.
GUID	Globally Unique Identifier — Microsoft’s term for UUID.	{3F25...C3301} COM-style format.
LF	Line Feed — newline control character (0x0A) used by Unix/Linux/macOS to terminate lines.	\n in text files; contrast with CR (0x0D) and CRLF (\r\n).
MIME	Multipurpose Internet Mail Extensions — standardized media types and encoding for content on the internet.	Content-Type: application/json; multipart/form-data with boundaries.
PEM	Privacy-Enhanced Mail — Base64 (PEM) encoding with header/footer lines for certs/keys.	-----BEGIN CERTIFICATE----- blocks; .pem/.crt/.key files.
UCS	Universal Character Set — ISO/IEC 10646 standard defining the full repertoire of Unicode code points; Unicode is kept synchronized with UCS.	UCS-2/UCS-4 historical encodings map to UTF‑16/UTF‑32; code points vs encodings distinction.
UTF	Unicode Transformation Format — encodings of Unicode code points (e.g., UTF‑8/UTF‑16/UTF‑32).	UTF‑8 is the dominant encoding on the web and in APIs.
UUID	Universally Unique Identifier — 128-bit unique ID.	UUID v4 random, v5 namespace.
Legacy
BCD	Binary-Coded Decimal — encoding that represents each decimal digit with its own binary nibble (4 bits), enabling precise decimal arithmetic.	Packed BCD in financial systems; CPU decimal adjust instructions (DAA/DAS).
MBCS	Multi-Byte Character Set — legacy variable-length encodings that use one or more bytes per character (often DBCS for CJK) prior to widespread Unicode adoption.	Windows "ANSI" code pages (Shift_JIS, EUC‑JP); prefer UTF‑8 today.
Historical
CR	Carriage Return — control character (0x0D) historically used to move the print head to column 0; used by classic Mac OS as line terminator.	\r in classic Mac text files; pairs with LF in CRLF on Windows.

Data Formats (Interchange)

Acronym	Meaning	Example
BSON	Binary JSON — binary serialization format with typed fields and efficient encoding designed for fast traversal and in-place updates.	MongoDB wire/storage format; supports types like ObjectId, Date, binary; drivers encode/decode BSON.
CBOR	Concise Binary Object Representation — compact, schema-optional binary data format designed for small code and message size (RFC 8949).	IoT/API payloads with maps/arrays; COSE for CBOR Object Signing and Encryption; diagnostic notation for debugging.
CSV	Comma-Separated Values — plain text tabular format.	users.csv exports/imports.
HDF5	Hierarchical Data Format version 5 — portable file format and library for storing large, complex, heterogeneous scientific data with groups/datasets and rich metadata.	Store arrays/tables/images with chunking/compression; used in scientific computing and ML datasets.
JSON	JavaScript Object Notation — data format.	{ "id": 1 } payloads.
JSON-LD	JSON for Linking Data — JSON‑based serialization for Linked Data/RDF that uses @context to map terms to IRIs and add semantics to JSON documents.	Embed schema.org with <script type="application/ld+json"> on web pages; exchange RDF graphs in JSON for knowledge graphs/APIs.
JSONL	JSON Lines — newline‑delimited JSON records for streaming/append‑friendly logs and datasets (aka NDJSON).	One JSON object per line; easy to process with line‑oriented tools.
netCDF	Network Common Data Form — self‑describing, portable data formats and libraries for array‑oriented scientific data; supports classic (CDF), 64‑bit offset, and netCDF‑4/HDF5.	Earth science datasets (grids/time series); interoperable with many scientific tools.
ORC	Optimized Row Columnar — columnar storage format optimized for analytics with predicate pushdown, compression, and statistics.	Store big data tables in ORC on Hadoop/Spark; efficient scans and compression.
OWL	Web Ontology Language — a family of knowledge representation languages for authoring ontologies, based on RDF and standardized by the W3C.	Define classes, properties, and relationships for a domain in an ontology.
RDF	Resource Description Framework — W3C model for describing and linking data using triples (subject–predicate–object), often serialized as Turtle/RDF/XML/JSON‑LD.	Knowledge graphs, linked data; schema.org markup via JSON‑LD.
RDFS	RDF Schema — a vocabulary for defining classes and properties for RDF data, providing a basic ontology framework.	rdfs:Class, rdfs:subClassOf, rdfs:domain, rdfs:range.
SKOS	Simple Knowledge Organization System — a W3C standard for representing knowledge organization systems like thesauruses and taxonomies.	Define concepts with skos:Concept and relationships like skos:broader.
SPARQL	SPARQL Protocol and RDF Query Language — the standard query language for RDF databases (triple stores).	SELECT ?s ?p ?o WHERE { ?s ?p ?o } to query a graph.
TSV	Tab-Separated Values — plain text tabular format using tabs as delimiters.	users.tsv exports with tab‑delimited fields.
Legacy
FOAF	Friend of a Friend — one of the earliest and most famous Semantic Web ontologies, used to describe people and their relationships.	Define a person's profile using foaf:Person, foaf:name, foaf:knows.
JSONP	JSON with Padding — legacy technique to circumvent same‑origin policy by wrapping JSON in a callback for script tags.	callback({ ... }) responses consumed via <script>; replaced by CORS.
MARC	Machine-Readable Cataloging — a standard for the representation and communication of bibliographic and related information in machine-readable form.	Library automation systems use MARC records to manage catalogs.
RSS	Really Simple Syndication — XML-based web feed format for publishing updates.	Blog feed at /feed.xml; subscribe in a feed reader.

Data Formats (Compression & Archival)

Acronym	Meaning	Example
7z	7‑Zip archive format — open archive container supporting solid compression, advanced filters, and high ratios via LZMA/LZMA2 and others.	Create/extract with 7z a archive.7z files/ and 7z x; widely used for high‑ratio packaging.
BZIP2	Burrows–Wheeler block-sorting compressor — high compression ratio with moderate CPU cost; slower than gzip, faster than xz in many cases.	Compress archives/logs: bzip2 file, tar -cjf archive.tar.bz2 dir/; .bz2 packages.
DEFLATE	Lossless compression format combining LZ77 sliding‑window dictionary with Huffman coding; ubiquitous in ZIP, gzip, and PNG.	Compress HTTP responses (Content‑Encoding: gzip/deflate), ZIP entries, and PNG image data.
GZIP	GNU Zip — widely used lossless compression format using DEFLATE (LZ77+Huffman); good balance of speed and ratio.	Compress streams/files: gzip file, tar -czf archive.tar.gz dir/; HTTP Content-Encoding: gzip.
JAR	Java ARchive — ZIP‑based archive format for packaging Java classes/resources and metadata (META-INF/MANIFEST.MF); supports signing and class‑path entries.	Build/run .jar apps (jar cfm app.jar MANIFEST.MF -C out/ .); libraries on the classpath; fat/uber JARs bundle deps.
LZ4	Extremely fast lossless compression algorithm optimized for speed with modest compression ratios.	Compress logs/IPC payloads with LZ4 for low latency; .lz4 frames.
LZ77	Lempel–Ziv 1977 — dictionary-based lossless compression using a sliding window and back‑references (length, distance) to past data.	Foundation for DEFLATE (gzip/ZIP) and many formats; emits literals and copy tokens.
LZMA	Lempel–Ziv–Markov chain Algorithm — high‑ratio lossless compression with larger memory use and slower speeds than DEFLATE; foundation for 7z and XZ (LZMA2).	Create 7z archives with LZMA/LZMA2; xz uses LZMA2 for .xz/.tar.xz.
RAR	Roshal Archive — proprietary archive format supporting solid compression, recovery records, and strong encryption; widely used but not fully open.	Create/extract with WinRAR/rar/unrar; .rar multi‑part volumes; consider 7z/zip for openness.
RLE	Run-Length Encoding — simple lossless compression that replaces runs of repeated symbols with a count and value.	Bitmap/scanline compression (e.g., BMP RLE, fax/CCITT variants); good for large uniform areas.
TAR	Tape ARchive — stream/archive format that bundles multiple files/directories with metadata into a single sequential archive; often compressed (e.g., .tar.gz/.tgz).	Create/extract backups: tar -czf backup.tgz dir/; used for packaging and distribution.
XZ	XZ Utils format — high‑ratio lossless compression using LZMA2 with solid archives and strong compression at the cost of CPU/time.	Compress release artifacts/logs: tar -cJf, xz -T0 file; .tar.xz packages in Linux distros.
ZIP	ZIP archive format — ubiquitous container supporting per‑file compression (typically DEFLATE), random access, and metadata; widely supported on all platforms.	.zip files; zip/unzip; JAR/APK/Office Open XML use ZIP containers.
ZSTD	Zstandard — modern fast lossless compression algorithm offering high ratios with very high decompression speed; supports dictionaries.	Compress artifacts/logs with zstd; .zst files; use dictionaries for small data.
Legacy
LZW	Lempel–Ziv–Welch — dictionary-based lossless compression algorithm historically used in GIF and some TIFF variants; now patent-free.	Classic GIF image compression; replace with PNG for lossless images.

Data Processing

Acronym	Meaning	Example
ACID	Atomicity, Consistency, Isolation, Durability — transaction guarantees.	Bank transfer completes fully or not at all.
ADO.NET	ActiveX Data Objects .NET — the modern data access framework for the .NET platform, succeeding classic ADO.	SqlConnection and DataSet for database operations in C#/VB.NET.
BASE	Basically Available, Soft state, Eventual consistency — distributed tradeoff.	Eventual consistency across regions.
BI	Business Intelligence — processes/tools to analyze business data for insights and decision‑making.	Dashboards and reports in Looker/Power BI over a warehouse.
BLOB	Binary Large Object — large binary field in a DB.	Store images/files as BLOBs or in object storage.
CAP	Consistency, Availability, Partition tolerance — favor two under partition.	AP systems may return stale data during splits.
CBO	Cost-Based Optimizer — query planner that chooses execution plans by estimating cost using statistics.	Analyze stats; planner picks index scan vs full scan.
CDC	Change Data Capture — stream DB changes.	Debezium publishes events to Kafka.
CRDT	Conflict-free Replicated Data Type — data structures that merge deterministically without coordination for eventual consistency.	LWW-Element-Set, G-Counter; collaborative docs with Automerge/Yjs.
CTE	Common Table Expression — named temporary result set referenced within a statement.	WITH recent AS (SELECT ...) SELECT * FROM recent WHERE ....
DB	Database — organized data managed by a DBMS.	Postgres/MySQL database with tables, indexes, and transactions.
DB2	DB2 — IBM's family of relational database management systems (RDBMS) running on platforms from Linux/Unix/Windows to mainframes (z/OS).	Enterprise data warehousing and OLTP on DB2 for z/OS or LUW.
DBMS	Database Management System — software that manages databases, provides storage, query, and transaction processing.	PostgreSQL, MySQL, SQLite, Oracle, SQL Server.
DDL	Data Definition Language — SQL for defining/modifying schema objects.	CREATE TABLE, ALTER TABLE, CREATE INDEX.
DLQ	Dead Letter Queue — holding queue/topic for messages/events that could not be processed or delivered after retries, isolating poison messages for inspection and remediation.	SQS redrive policy sends failed messages to a DLQ; Kafka error/"-dlq" topic.
DML	Data Manipulation Language — SQL for querying and changing data.	SELECT, INSERT, UPDATE, DELETE.
DW	Data Warehouse — centralized, integrated repository optimized for analytics.	Snowflake/BigQuery/Redshift with star/snowflake schemas.
EF	Entity Framework — Microsoft's object-relational mapping (ORM) framework for .NET.	Map database tables to C# objects with EF Core; use LINQ to query data.
ELT	Extract, Load, Transform — load raw data then transform in the warehouse.	Modern ELT with dbt/BigQuery.
ERD	Entity Relationship Diagram — visual schema modeling notation that captures entities, their attributes, and relationships/cardinalities before implementing a database.	Sketch an ERD in crow's-foot notation to model Customer–Order–OrderLine relationships prior to creating tables.
ETL	Extract, Transform, Load — data integration pipeline.	Batch load to data warehouse.
FK	Foreign Key — constraint that enforces referential integrity by requiring values to exist in a referenced table.	orders.user_id references users.id; ON DELETE CASCADE.
GIS	Geographic Information System — system for capturing, storing, analyzing, and managing spatial or geographic data.	Analyze spatial data with ArcGIS or QGIS; build location-aware apps.
HLL	HyperLogLog — probabilistic algorithm for cardinality (distinct count) estimation that uses fixed, small memory with tunable relative error via stochastic averaging of leading-zero counts.	Approximate unique users/events with ~1–2% error using kilobytes of memory; streaming distinct counts in analytics pipelines.
LSMT	Log-Structured Merge-Tree — write-optimized indexing/storage structure that buffers writes in memory and flushes them as sorted runs (SSTables) to disk, with background compaction/merging; lowers random writes at the cost of read/space amplification.	Used by LevelDB/RocksDB; LSM-based stores like Cassandra and HBase.
MQ	Message Queue — durable, asynchronous messaging channel that buffers messages between producers and consumers to decouple services and smooth load.	RabbitMQ/SQS enqueue events; workers consume from the queue to process jobs off the critical path.
MVCC	Multi-Version Concurrency Control — concurrency control that lets readers and writers proceed by keeping multiple row versions and using snapshot visibility rules.	PostgreSQL snapshot reads; VACUUM removes obsolete versions.
NoSQL	Non-relational DBs: documents, key-values, graphs, wide columns.	MongoDB, Redis, Cassandra.
OLAP	Online Analytical Processing — read-heavy analytics.	BI cubes, columnar stores.
OLTP	Online Transaction Processing — write-heavy transactions.	Order processing systems.
PK	Primary Key — unique, non-null identifier for a table row.	users(id UUID PRIMARY KEY); composite keys across columns.
RDBMS	Relational Database Management System — DBMS based on the relational model using tables, rows, and SQL with constraints and ACID transactions.	PostgreSQL, MySQL, SQL Server, Oracle; normalized schemas and joins.
RDD	Resilient Distributed Dataset — fault-tolerant distributed collection in Apache Spark enabling parallel transformations across partitions with lineage-based recovery.	Spark job transforms an RDD with rdd.map()/filter() and caches it via persist() for reuse.
SQL	Structured Query Language — query/manage relational DBs.	SELECT * FROM users.
WAL	Write-Ahead Logging — durability mechanism that writes log records before data pages.	PostgreSQL WAL for crash recovery and replication.
Legacy
ADO	ActiveX Data Objects — a legacy Microsoft data access framework for connecting to databases from languages like classic VB and ASP.	ADODB.Connection and Recordset objects for database queries.
CICS	Customer Information Control System — IBM mainframe transaction processing monitor that provides high-volume, secure, and reliable online transaction processing.	Legacy banking and airline systems running CICS transactions.
CODASYL	Conference/Committee on Data Systems Languages — consortium behind COBOL and the DBTG network database model that specified schemas, subschemas, and navigation APIs for early DBMS.	CODASYL DBTG specs defined the network data model adopted by IDS, IDMS, and other mainframe DBMSs.
DAO	Data Access Objects — a legacy Microsoft data access API primarily used for accessing Jet (Microsoft Access) databases.	Predecessor to ADO; used heavily in classic VB applications.
IDMS	Integrated Database Management System — commercial network database derived from IDS, providing CODASYL DBTG-compliant data/navigation on IBM mainframes.	CA-IDMS on IBM z/OS runs core enterprise apps using CODASYL sets and schemas.
IDS	Integrated Data Store — Charles Bachman’s pioneering network database management system for GE mainframes, influencing CODASYL DBTG standards and later products like IDMS.	Run IDS/II on GE 600/635 systems to model hierarchical/network data; precursor to commercial IDMS releases.
IMS	Information Management System — IBM's combined hierarchical database and transaction manager for mainframes, a precursor to relational databases.	High-performance transaction processing on z/OS; IMS DB/DC.
OLE DB	Object Linking and Embedding, Database — a low-level Microsoft API for accessing a wide variety of data sources.	The underlying interface for ADO; connect to SQL Server via the OLE DB provider.
RDO	Remote Data Objects — a legacy Microsoft data access API for remote relational databases, superseded by ADO.	Early client-server applications in Visual Basic connecting to SQL Server.
VSAM	Virtual Storage Access Method — the primary data storage method on IBM z/OS for structured data.	Key-sequenced datasets (KSDS) used by CICS and batch applications.

Artificial Intelligence

Acronym	Meaning	Example
AI	Artificial Intelligence — techniques that enable machines to perform tasks associated with human intelligence (learning, perception, reasoning).	Use ML/DL models to power AI features like recommendations.
ANN	Artificial Neural Network — computational model inspired by biological neurons, used for function approximation and pattern recognition.	MLPs for tabular data; feedforward nets for classification.
CNN	Convolutional Neural Network — neural network architecture specialized for grid‑like data using convolutional filters.	Image classification/segmentation models.
CoT	Chain-of-Thought — prompting technique to elicit step-by-step reasoning.	"Let's think step by step" to improve math/logic.
GPT	Generative Pre-trained Transformer — transformer-based LLM architecture pre-trained on large text corpora and fine-tuned for tasks.	GPT-4 class models for chat, code, and reasoning.
LLM	Large Language Model — NLP model for generation/reasoning.	GPT/Llama used via APIs or locally.
MCP	Model Context Protocol — open protocol to expose tools/data to LLM clients via standardized servers.	Run an MCP server to provide DB/filesystem tools to an LLM client.
MoE	Mixture of Experts — sparse expert routing to scale parameters with near-constant compute.	Router selects top‑k experts per token (Switch-Transformer).
NER	Named Entity Recognition — extract and label entities in text.	Tag PERSON/ORG/LOC from documents.
NLP	Natural Language Processing — techniques for understanding and generating human language.	Text classification, NER, summarization, translation.
OCR	Optical Character Recognition — convert images/scans of text into machine‑encoded text using computer vision and sequence models.	Tesseract or deep‑learning OCR to extract text from documents/receipts.
RAG	Retrieval-Augmented Generation — ground model outputs by retrieving external knowledge at query time.	Retrieve top‑k docs from a vector store and include them in the prompt.
RL	Reinforcement Learning — learning by interaction with an environment via rewards.	Q‑learning, policy gradients; RLHF for model alignment.
RLHF	Reinforcement Learning from Human Feedback — align models using human preference signals via a learned reward model.	Collect preference pairs, train a reward model, then fine‑tune with PPO.
RNN	Recurrent Neural Network — sequence model with recurrent connections.	LSTM/GRU for language modeling and time series.
SFT	Supervised Fine-Tuning — fine‑tune a pretrained model on labeled input–output pairs to specialize behavior.	Fine‑tune a base LLM on instruction datasets before RLHF.
TTS	Text-to-Speech — synthesize speech audio from text.	Generate spoken responses from a chatbot.
VLM	Vision-Language Model — jointly processes images and text.	CLIP, BLIP, LLaVA for captioning and VQA.

Reliability & Operations

Acronym	Meaning	Example
DR	Disaster Recovery — restore service after catastrophic failure.	DR runbooks; backup restore drills.
HA	High Availability — design to minimize downtime.	Multi-zone deployment with failover.
MTTR	Mean Time To Repair/Recover — restore time after failure.	Track MTTR per incident.
RCA	Root Cause Analysis — identify underlying cause.	Postmortem documents.
RPO	Recovery Point Objective — max acceptable data loss.	5-minute RPO via frequent backups.
RTO	Recovery Time Objective — target restore time.	30-minute RTO for tier-1 services.
SLA	Service Level Agreement — contractual target.	99.9% monthly uptime.
SLI	Service Level Indicator — measured metric.	Request success rate, p95 latency.
SLO	Service Level Objective — internal target.	99.95% quarterly availability.
SPOF	Single Point Of Failure — outage if it fails.	Single DB primary without replica.
SRE	Site Reliability Engineering — SWE meets ops.	Error budgets, toil reduction.

Performance & Metrics

Acronym	Meaning	Example
Apdex	Application Performance Index — satisfaction score based on latency thresholds.	Apdex ≥ 0.9 target.
APM	Application Performance Monitoring — traces/metrics/errors for apps.	Distributed tracing spans across services.
CLS	Cumulative Layout Shift — visual stability (Web Vitals).	CLS < 0.1.
FLOPS	Floating-Point Operations Per Second — measure of compute performance for CPUs/GPUs/accelerators.	GPU rated at 30 TFLOPS; benchmark sustained vs peak GFLOPS.
FPS	Frames Per Second — render/update frequency for graphics/video; higher is smoother within latency/refresh constraints.	Games target 60+ FPS; VR aims for 90–120 FPS.
INP	Interaction to Next Paint — user input responsiveness (Web Vitals).	INP < 200 ms.
IOPS	Input/Output Operations Per Second — storage throughput measurement.	NVMe SSD sustaining 500k+ random read IOPS.
IPC	Instructions Per Clock/Cycle — measure of a CPU's architectural efficiency, independent of clock speed.	A CPU with higher IPC can be faster than one with a higher clock rate.
LCP	Largest Contentful Paint — main content render time (Web Vitals).	LCP < 2.5 s.
LoC	Lines of Code — simple size metric counting source lines; can indicate scope but is a poor proxy for complexity or value.	Compare module sizes; avoid using LoC alone for productivity.
MIPS	Million Instructions Per Second — rough measure of integer instruction throughput; varies widely by ISA and instruction complexity.	Historical CPU comparisons; not comparable across architectures/workloads.
P50/P95/P99	Latency percentiles — response time distribution.	P95 latency under 250 ms.
RPS/QPS	Requests/Queries Per Second — service throughput.	API serves 2k RPS at peak.
RUM	Real User Monitoring — measurements from real users.	In-browser beacons for Web Vitals.
TPS	Transactions Per Second — business-level throughput.	Payments at 150 TPS during sale.
TTFB	Time To First Byte — time to first response byte.	Aim for TTFB < 200 ms.
TTI	Time To Interactive — page becomes reliably usable.	TTI ~ 3.0 s.

Networking & Protocols

Acronym	Meaning	Example
AMQP	Advanced Message Queuing Protocol — open standard for asynchronous messaging between applications, enabling reliable, interoperable, and feature-rich communication.	RabbitMQ/ActiveMQ brokers implementing AMQP 0-9-1 or 1.0 for queuing and routing.
ARP	Address Resolution Protocol — map IP addresses to MAC addresses on a LAN.	ARP cache; gratuitous ARP.
AS	Autonomous System — a collection of IP networks under a single administrative control, identified by an ASN and used in BGP routing.	An ISP, a university, or a large tech company's network.
ASN	Autonomous System Number — a globally unique identifier for a network, used in BGP routing.	ISP route announcements include their ASN; AS15169 is Google's ASN.
BGP	Border Gateway Protocol — inter-domain routing protocol of the internet.	ISP peering and route advertisements.
BIND	Berkeley Internet Name Domain — a widely used, open-source DNS server.	Configure zones in named.conf; query a BIND server with dig.
BPF	Berkeley Packet Filter — kernel-level virtual machine for packet filtering/observability (eBPF on modern kernels).	Capture packets with tcpdump; eBPF programs for tracing.
CIDR	Classless Inter-Domain Routing — notation for IP prefixes and aggregation.	10.0.0.0/16 VPC; subnetting /24; route summarization.
CNAME	Canonical Name — DNS record that aliases one hostname to another.	www CNAME to example.com; avoid at zone apex without ALIAS/ANAME.
CLNP	Connectionless Network Protocol — OSI layer 3 datagram protocol (ISO/IEC 8473) that provides connectionless packet delivery using NSAP addressing within OSI stacks.	DECnet/OSI and X.25 backbones carried CLNP traffic with IS-IS routing NSAP-addressed packets between hosts.
NSAP	Network Service Access Point — OSI network-layer address format carrying AFI/IDI and DSP fields used by CLNP/IS-IS instead of IP addresses.	An OSI host might use NSAP 49.0001.1921.6800.1001.00 with IS-IS routing NSAP prefixes across an OSI backbone.
CR-LDP	Constraint-Based Routed Label Distribution Protocol — MPLS TE signaling that extends LDP with constraint advertisement and explicit route objects to set up engineered LSPs without RSVP.	Some carriers historically deployed CR-LDP to establish bandwidth-guaranteed LSPs before migrating to RSVP-TE.
CRC	Cyclic Redundancy Check — an error-detecting code used to detect accidental changes to digital data.	Ethernet frame check sequence (FCS); CRC-32 in ZIP/PNG files.
DHCP	Dynamic Host Configuration Protocol — automatic IP configuration.	DHCP assigns IP/gateway/DNS.
DHT	Distributed Hash Table — decentralized key-value store that partitions data across a peer-to-peer network, enabling scalable lookups without a central server.	BitTorrent Mainline DHT for peer discovery; IPFS for content addressing.
DoH	DNS over HTTPS — perform DNS resolution over HTTPS for privacy/integrity.	https://dns.google/dns-query DoH endpoint.
DWDM	Dense Wavelength Division Multiplexing — optical multiplexing technique that carries many tightly spaced light wavelengths on a single fiber pair to massively increase backbone capacity.	Telco long-haul links stack 100G/400G channels with DWDM mux/demux gear and optical amplifiers.
FC	Fibre Channel — high‑speed serial transport for storage networking (SANs) with switched fabrics, typically 8/16/32 Gbit/s, carrying SCSI/FCP.	Connect hosts to SAN arrays over FC via HBAs and switches; zoning and LUN masking.
FDDI	Fiber Distributed Data Interface — ANSI token-ring LAN standard operating at 100 Mbit/s over dual counter-rotating fiber rings with timed token passing and built-in redundancy; once popular for campus backbones before Fast/Gigabit Ethernet.	Interconnect building LANs via FDDI dual rings, with automatic wrap-around on fiber breaks to maintain service.
HDLC	High-Level Data Link Control — ISO bit-oriented layer 2 protocol using frame flag delimiters, bit stuffing, and sliding-window ARQ; foundation for derivatives like SDLC, LAPB, PPP, and Frame Relay.	Serial WAN links encapsulating packets in HDLC frames; routers using Cisco HDLC or LAPD signaling over ISDN.
HTTP	Hypertext Transfer Protocol — web application protocol.	GET /index.html over TCP.
HTTPS	HTTP over TLS — encrypted HTTP.	Padlock in browsers.
ICMP	Internet Control Message Protocol — diagnostics/control.	ping uses Echo Request/Reply.
IMAP	Internet Message Access Protocol — email retrieval/sync.	Mail clients syncing mailboxes.
IP	Internet Protocol — addressing/routing (IPv4/IPv6).	Packet delivery across networks.
IPsec	Internet Protocol Security — suite of protocols for authenticating and encrypting IP packets at the network layer (AH/ESP) with key exchange via IKE.	Site-to-site or remote-access VPNs using IKEv2 with ESP in tunnel mode; transport mode for host-to-host.
iSCSI	Internet Small Computer Systems Interface — block storage protocol that encapsulates SCSI commands over TCP/IP.	Connect initiators to targets on port 3260; boot from SAN; map LUNs over the network.
ISP	Internet Service Provider — company that provides internet connectivity and related services.	Residential broadband, business fiber links, and transit.
L2TP	Layer 2 Tunneling Protocol — encapsulates PPP frames to create tunnels across IP networks, typically paired with IPsec for encryption/authentication.	Remote-access VPN uses L2TP over IPsec (UDP 1701/500/4500) to tunnel client traffic through a secure gateway.
LAN	Local Area Network — network covering a limited geographic area such as a home, office, or campus.	Ethernet/Wi‑Fi LAN with switches and access points.
LDAP	Lightweight Directory Access Protocol — protocol for accessing and managing directory services.	Authenticate/lookup users and groups in an LDAP directory.
LDP	Label Distribution Protocol — MPLS control plane that advertises label bindings between neighbors to build label-switched paths based on IGP routes without explicit traffic engineering.	ISPs run LDP over their IGP so MPLS L3VPNs follow OSPF/IS-IS shortest paths by default.
LSP	Label-Switched Path — the unidirectional MPLS forwarding path created by label bindings that steer packets hop by hop through an MPLS network.	Traffic for a VPN flows along an LSP signaled by LDP or RSVP-TE from ingress PE to egress PE.
MAC	Media Access Control — data-link sublayer that governs medium access, framing, and addressing on LANs.	Ethernet MAC handles frame delimiting, MAC addressing, and channel access.
MPLS	Multiprotocol Label Switching — high-performance packet forwarding that uses short labels to make traffic-engineered L2.5 paths across provider cores.	ISP backbone uses MPLS L3VPNs/TE to steer customer traffic and provide QoS across the WAN.
MPLS-TE	MPLS Traffic Engineering — extensions that compute constraint-based LSPs using RSVP-TE/CR-LDP to steer traffic along engineered paths that meet bandwidth, affinity, and protection requirements.	Carriers pin backup-capable label-switched paths around congested links using RSVP-TE with fast reroute.
MQTT	Message Queuing Telemetry Transport — lightweight publish-subscribe protocol for constrained devices and low-bandwidth, high-latency networks; widely used in IoT.	IoT sensors publishing telemetry to an MQTT broker; mobile push notifications.
MTU	Maximum Transmission Unit — largest payload size (in bytes) that can be sent in a single layer‑2 frame without fragmentation.	Ethernet MTU 1500; jumbo frames MTU 9000; Path MTU Discovery avoids fragmentation.
MX	Mail Exchanger — DNS record that specifies the mail servers responsible for accepting email for a domain, with preferences for priority/failover.	example.com. MX 10 mail1.example.com. and MX 20 mail2.example.com. as backup.
NAT	Network Address Translation — remap private to public addresses.	Home routers performing PAT.
NFS	Network File System — distributed file system protocol for sharing files over a network.	Mount remote directories via NFSv3/NFSv4.
NS	Name Server — DNS server authoritative for a zone; also the DNS record type that delegates to authoritative servers.	NS records pointing to ns1.example.com for a domain.
NTP	Network Time Protocol — synchronize clocks over networks using a hierarchy of time sources.	chrony/ntpd syncing to NTP servers (stratum levels).
OSI	Open Systems Interconnection — conceptual seven‑layer networking reference model for describing protocols and interoperability (Layers 1–7: Physical→Application).	Map protocols to layers (e.g., Ethernet=L2, IP=L3, TCP=L4, HTTP=L7); teaching/troubleshooting taxonomy.
OSPF	Open Shortest Path First — interior gateway routing protocol.	Multi-area OSPF in enterprises.
OTN	Optical Transport Network — ITU-T G.709 digital wrapper standard that multiplexes client signals into optical channels with forward error correction and management for carrier backbones.	Carriers groom Ethernet/SONET traffic into ODUk containers and transport them over OTU4 wavelengths with OTN switches.
P2P	Peer-to-Peer — decentralized communication model where nodes act as both clients and servers without a central coordinator.	BitTorrent swarms; WebRTC data channels; DHT-based peer discovery.
PoE	Power over Ethernet — standard for providing electrical power through Ethernet cables to devices like IP cameras, VoIP phones, and wireless access points.	802.3af/at/bt standards for PoE/PoE+/PoE++.
QoS	Quality of Service — mechanisms that classify and prioritize traffic to meet latency, jitter, and loss requirements.	Configure DiffServ/DSCP queues on routers to give voice and video higher priority than bulk data.
QUIC	Quick UDP Internet Connections — encrypted, multiplexed transport over UDP.	HTTP/3 runs over QUIC.
RDP	Remote Desktop Protocol — a proprietary protocol from Microsoft for remote access to a graphical user interface on a Windows machine.	Connect to a Windows server with an RDP client; mstsc.exe.
RSVP-TE	Resource Reservation Protocol - Traffic Engineering — MPLS control-plane signaling that establishes label-switched paths with bandwidth reservations using RSVP extensions for constraints, fast reroute, and preemption.	Configure RSVP-TE tunnels between provider edge routers to reserve 10 Gbit/s paths with explicit hop lists and standby LSPs.
SDH	Synchronous Digital Hierarchy — ITU-T optical transport standard harmonizing SONET internationally with STM/STM-N rates, VC containers, and automatic protection switching for carrier backbones.	European telcos running STM-16/STM-64 rings that interop with SONET via gateways; metro networks reroute around fiber faults in <50 ms.
SFTP	SSH File Transfer Protocol — file transfer over SSH.	sftp user@host uploads/downloads.
SMB	Server Message Block — network file/printer sharing protocol used mainly by Windows; modern versions (SMBv2/v3) support signing/encryption.	Mount \\server\share; Samba on Unix; avoid SMBv1 due to security issues.
SMTP	Simple Mail Transfer Protocol — send email.	MTA relaying messages.
SNMP	Simple Network Management Protocol — protocol for monitoring and managing networked devices via a hierarchical MIB of OIDs, supporting polling and asynchronous traps/informs.	Poll interfaces/CPU via GET/GETNEXT/GETBULK; receive traps; v1/v2c (community) and v3 (auth/privacy).
SONET	Synchronous Optical Network — ANSI fiber transport standard using time-division multiplexed frames (STS/OC rates) with built-in protection switching; interoperable internationally via ITU-T SDH.	Telco backbones delivering OC-3/OC-12/OC-192 rings for voice/data; metro rings that auto-switch on fiber cuts.
SR-MPLS	Segment Routing over MPLS — control plane that encodes segment routing label stacks in MPLS to replace LDP/RSVP, enabling source-routed paths, traffic engineering, and fast reroute with simplified signaling.	Deploy SR-MPLS in a service provider core so ingress routers push segment lists to steer L3VPN traffic without RSVP-TE.
SRv6	Segment Routing over IPv6 — segment routing data plane that encodes instruction lists in IPv6 Segment Routing Headers (SRH), enabling source-routed paths, service chaining, and traffic engineering without MPLS labels.	Use SRv6 in a SP core so packets carry SID lists (2001:db8::A, ::B) to steer flows through specific functions or nodes; integrate with SRv6 TE and network programming.
SSE	Server-Sent Events — HTTP-based server→client stream.	EventSource('/events').
STP	Spanning Tree Protocol — network protocol that ensures a loop-free topology for bridged Ethernet networks.	Switches running STP/RSTP to prevent broadcast storms.
TCP	Transmission Control Protocol — reliable byte stream.	HTTP, TLS use TCP.
TCP/IP	Transmission Control Protocol / Internet Protocol — foundational internet protocol suite encompassing transport, network, and related layers.	Classic network stack model; "TCP/IP networking" on UNIX systems.
TLD	Top-Level Domain — the highest level in the DNS hierarchy, forming the rightmost label of a domain name.	.com, .org, country-code TLDs like .uk; ICANN-managed root zone.
TTL	Time To Live — lifetime for packets/cached records.	DNS TTL controls cache duration.
UDP	User Datagram Protocol — connectionless, low-latency.	DNS, streaming.
UNC	Universal Naming Convention — Windows network path notation for accessing resources by server/share.	\\\\server\\share\\folder\\file.txt; used with SMB.
VLAN	Virtual Local Area Network — Layer 2 network segmentation on a switch, isolating broadcast domains; tagging via IEEE 802.1Q.	VLAN 10/20 on access/trunk ports; tagged vs untagged frames.
WAN	Wide Area Network — network spanning large geographic areas interconnecting LANs over provider links or the public internet.	MPLS links, SD‑WAN, site‑to‑site VPN between offices.
WebRTC	Web Real-Time Communication — a framework providing browsers and mobile applications with real-time communication (RTC) capabilities via simple APIs.	Peer-to-peer video conferencing, screen sharing, and data channels in the browser.
WHOIS	WHOIS protocol — query/response protocol for retrieving registration information about internet resources such as domain names and IP address allocations.	whois example.com to get registrar/registrant data; RDAP is the modern HTTP-based successor.
WS	WebSocket — full-duplex over single TCP connection.	ws://example.com/socket.
WSS	WebSocket Secure — WebSocket over TLS.	wss://example.com/socket.
Legacy
ADSL	Asymmetric Digital Subscriber Line — a common type of DSL where download speeds are faster than upload speeds.	Consumer broadband over telephone lines.
CSU	Channel Service Unit — legacy telco/customer-premises device that terminates a digital leased circuit, provides line conditioning/loopback diagnostics, and hands off a clean interface to a paired DSU or router.	Standalone CSU on a T1 line or integrated CSU/DSU modules in enterprise routers delivering telco-managed point-to-point links.
DCE	Data Circuit-terminating Equipment — provides clocking, signal conversion, and circuit termination for serial/WAN links so attached DTEs can communicate.	CSU/DSU, cable/DSL modems, and telco demarc gear act as the DCE in leased-line setups.
DSL	Digital Subscriber Line — a family of technologies for transmitting digital data over telephone lines.	ADSL, SDSL, VDSL are all types of DSL.
DSU	Data Service Unit — legacy digital modem that converts the CSU-provided line signal into synchronous serial presented to DTE gear, completing the CSU/DSU pair on leased circuits.	External DSUs or router interface cards carrying T1/E1 circuits expose V.35/RS-449 ports for routers/terminals.
DTE	Data Terminal Equipment — end device that connects to a DCE to originate or receive data on a serial/WAN circuit, typically providing clocking recovery from the DCE.	Routers, terminals, or customer-edge gear plugging into a CSU/DSU; use show controllers serial to verify DTE/DCE role via cable pinout.
FTP	File Transfer Protocol — legacy, unencrypted by default.	ftp client for file transfers.
FTPS	FTP over TLS — encrypted FTP.	Implicit/explicit FTPS modes.
iPXE	Open-source network boot firmware/bootloader extending PXE with HTTP(S), iSCSI, FCoE, AoE, scripts, and TLS.	Chainload iPXE via PXE; fetch an HTTPS boot script to load kernel/initrd.
IRC	Internet Relay Chat — real-time text messaging protocol and networks for group channels and direct messages.	Join #project on Libera Chat using irssi or WeeChat.
NBT	NetBIOS over TCP/IP — transport that carries NetBIOS name, datagram, and session traffic over TCP/UDP (ports 137–139) so legacy NetBIOS applications work on IP networks.	Keep NBT only for backward compatibility with old Windows clients/printers; disable when moving fully to DNS/SMB over TCP 445.
NetBEUI	NetBIOS Extended User Interface — non-routable, broadcast-heavy transport protocol for NetBIOS communications on small LANs; superseded by NBT/TCP/IP.	Early Windows peer-to-peer networking used NetBEUI; administrators removed it when migrating to TCP/IP-based SMB.
NetBIOS	Network Basic Input/Output System — legacy API and naming services that provided session/datagram communication atop early LAN transports (NetBEUI, IPX/SPX, later NBT).	DOS/Windows for Workgroups apps used NetBIOS names for SMB file/print sharing; modern AD domains phase out NetBIOS names in favor of DNS.
NIS	Network Information Service — a legacy Unix directory service for distributing system configuration data like user and host names between computers on a network.	Originally known as Yellow Pages (YP); superseded by LDAP.
NNTP	Network News Transfer Protocol — application protocol for distributing, querying, and posting Usenet articles over TCP.	Connect to Usenet servers on 119 (or 563 for NNTPS) to read/post news.
POP3	Post Office Protocol v3 — simple email retrieval.	Fetch-and-delete mailbox flow.
PPP	Point-to-Point Protocol — data link layer protocol for encapsulating network traffic over serial links; supports authentication, compression, and multilink.	Dial-up links; PPPoE for broadband; CHAP/PAP authentication.
PPTP	Point-to-Point Tunneling Protocol — legacy VPN tunneling protocol that encapsulates PPP over GRE with MPPE encryption; considered insecure and deprecated.	Historical Windows VPNs using PPTP; replace with IPsec/OpenVPN/WireGuard/L2TP over IPsec.
PXE	Preboot Execution Environment — standard for network booting clients using DHCP/BOOTP to obtain boot info and TFTP/HTTP to fetch boot loaders/images.	PXE boot a workstation from a provisioning server into an installer.
RIP	Routing Information Protocol — distance-vector interior gateway protocol using hop count as its metric with periodic full-table updates.	RIP v2 on small LANs; max 15 hops; split horizon/poison reverse to mitigate loops.
RLOGIN	Remote Login — BSD plaintext remote login protocol; superseded by SSH.	rlogin host for interactive sessions on legacy UNIX systems.
RSH	Remote Shell — BSD plaintext remote command execution; superseded by SSH.	rsh host command on legacy UNIX; avoid due to lack of security.
TFTP	Trivial File Transfer Protocol — simple UDP-based file transfer protocol commonly used for network boot and configuration.	PXE firmware downloads boot images via TFTP; no auth/encryption.
UPnP	Universal Plug and Play — discovery and control protocols for devices/services on a local network; includes IGD for NAT port mappings.	Home routers auto‑open ports via UPnP IGD; device discovery/control on LANs.
VDSL	Very-high-bit-rate Digital Subscriber Line — a faster version of DSL, often used for fiber-to-the-curb deployments.	Higher speeds over shorter distances than ADSL.
WINS	Windows Internet Name Service — Microsoft's legacy database-backed NetBIOS name resolution service that replicates between servers and integrates with DHCP for old Windows clients.	Maintain WINS servers in mixed Active Directory environments; DHCP option 44/46 hands out WINS server IPs to legacy nodes.
XMPP	Extensible Messaging and Presence Protocol — open, federated XML-based protocol for instant messaging and presence.	Jabber, Google Talk (legacy); used in federated chat and IoT.
Historical
AIM	AOL Instant Messenger — a pioneering instant messaging service from AOL, popular in the late 1990s and 2000s.	Buddy Lists, away messages, and chat sounds.
ARPANET	Advanced Research Projects Agency Network — pioneering packet‑switched network and direct precursor to the modern Internet.	1969 UCLA–SRI link; IMPs; 1983 cutover from NCP to TCP/IP.
ATM	Asynchronous Transfer Mode — a telecommunications standard for cell-based switching, designed for high-speed voice, video, and data.	Used in telco backbones and for DSL; superseded by IP-based networks.
BBS	Bulletin Board System — pre‑web dial‑up systems.	Modem dial‑ins for forums/files before the web.
BITNET	Because It’s Time Network — early academic store-and-forward network linking universities via leased lines using IBM’s RSCS protocol; provided email, file transfer, and LISTSERV mailing lists.	Colleges connected mainframes to BITNET in the 1980s; LISTSERV communities flourished before widespread internet access.
USENET	User Network — decentralized, distributed discussion system operating via the UUCP and later NNTP protocols, enabling newsgroups and threaded conversations across servers worldwide.	1980s/1990s communities exchanged posts in comp.*, sci.*, alt.* newsgroups replicated between sites; content accessible via NNTP readers.
BOOTP	Bootstrap Protocol — assigns IP configuration to diskless clients at boot, predecessor to DHCP.	Network boot ROM requests IP/gateway/TFTP server; largely replaced by DHCP.
CSMA/CD	Carrier-Sense Multiple Access with Collision Detection — media access control method used by early Ethernet on a shared bus.	Half-duplex hubs; nodes listen before transmitting and detect collisions.
CSNET	Computer Science Network — an early computer network that provided services to university computer science departments, funded by the NSF.	A key stepping stone between ARPANET and the modern internet.
CYCLADES	French research packet-switching network (CYCLADES project) that pioneered datagrams, host responsibility for reliability, and end-to-end design principles that influenced TCP/IP.	1970s French R&D network connecting CYCLADES hosts via CIGALE routers; experience informed the Internet's datagram model.
DECnet	Digital Equipment Corporation's proprietary network protocol suite for DEC systems; largely superseded by TCP/IP.	VAX/VMS clusters and DEC systems communicating over DECnet Phase IV/V.
ICQ	"I Seek You" — one of the first internet-wide instant messaging services.	User identification numbers (UINs) and the "uh-oh!" sound.
JANET	Joint Academic Network — the UK’s national research and education network providing high-speed connectivity and services for universities, colleges, and research institutions.	JANET interconnects UK campuses, data centers, and global research networks via the backbone operated by Jisc.
IPX	Internetwork Packet Exchange — Novell's network-layer protocol used with SPX and NetWare; replaced by IP in modern networks.	Legacy NetWare LANs using IPX addressing and routing.
ISDN	Integrated Services Digital Network — circuit‑switched digital telephony offering voice and data over PSTN with separate bearer/signaling channels.	BRI (2B+D) for small sites; PRI (23B+D NA / 30B+D EU) for trunks.
MILNET	Military Network — the DoD-operated segment of the ARPANET split off in 1983 to carry unclassified military traffic while academic research continued on the remaining ARPANET.	MILNET backbone connected defense sites and gateways, later evolving into the Defense Data Network and precursors to NIPRNet.
MSN	The Microsoft Network — an early online service and ISP from Microsoft, later known for its web portal and instant messenger.	MSN Messenger was a major competitor to AIM and ICQ.
NCP	NetWare Core Protocol — Novell NetWare file/print service protocol suite running over IPX/SPX (later IP).	Legacy NetWare clients mapping drives/printers via NCP.
NCP	Network Control Program — early ARPANET host protocol providing a transport layer and flow control prior to the adoption of TCP/IP.	Used until the 1983 flag day cutover to TCP/IP; sockets over NCP.
NDS	Novell Directory Services — directory service for managing identities, resources, and access in Novell NetWare environments (later evolved into eDirectory).	Centralized users/groups/policies across NetWare; replaced/renamed as eDirectory.
NSFNET	National Science Foundation Network — U.S. government-funded backbone that expanded academic access to the ARPANET successor, catalyzing the transition to today’s commercial internet before its 1995 decommissioning.	Regional networks connected to NSFNET T1/T3 backbones; commercial ISPs emerged as NSFNET traffic opened to broader use.
PAD	Packet Assembler/Disassembler — X.25-era device that buffered character-stream or async terminal traffic and converted it to packets for a public data network (and vice versa).	Retail POS terminals or green-screen async devices connected through a PAD to reach hosts over public X.25 services.
PUP	PARC Universal Packet — early internetworking protocol suite developed at Xerox PARC that influenced XNS and later networking concepts.	Historical LAN internetworking; precursor to concepts adopted in later stacks.
RARP	Reverse Address Resolution Protocol — legacy protocol for discovering an IP address given a MAC address.	Early diskless boot; superseded by BOOTP/DHCP.
SDLC	Synchronous Data Link Control — IBM's bit-oriented data link layer protocol for SNA networks, using poll/select over multi-drop lines; superseded by HDLC-derived standards and TCP/IP transports.	Host mainframes controlling remote 3270/3780 cluster controllers across leased lines via SDLC.
SLIP	Serial Line Internet Protocol — simple encapsulation of IP over serial links; lacks features like authentication, negotiation, and error detection.	Early dial-up IP connectivity; superseded by PPP.
SNA	Systems Network Architecture — IBM's proprietary networking architecture for mainframes and enterprise networks; largely superseded by TCP/IP.	IBM 3270/5250 terminals and LU types; later SNA over IP via Enterprise Extender.
SPX	Sequenced Packet Exchange — Novell's transport-layer protocol running over IPX, analogous to TCP; superseded by TCP/IP.	NetWare clients/servers using IPX/SPX for file/print services.
UUCP	Unix-to-Unix Copy Protocol — store-and-forward system for transferring files, email, and netnews over dial-up/serial links; pre-internet era networking.	Early email/news via bang paths (uucp!host!user); largely replaced by SMTP/NNTP over IP.
UUNET	Unix-to-Unix Network — one of the first commercial internet service providers, evolving from a Usenet feed service into a major backbone operator that helped commercialize internet access.	Provided UUCP/Usenet feeds, then IP transit and dial-up services before mergers into MCI/WorldCom.
WAIS	Wide Area Information Servers — early distributed document indexing/search and retrieval system predating modern web search; used client/server over Z39.50.	1990s internet search across WAIS servers before mainstream web engines.
X.25	ITU-T legacy packet-switched WAN protocol using virtual circuits over carrier networks; superseded by Frame Relay/ATM/IP.	Early bank/pos/leased-line links using X.25 PADs and PVC/SVC connections.
XNS	Xerox Network Systems — Xerox's network protocol suite from PARC that influenced later protocols (e.g., IPX/SPX, AppleTalk).	Historical LAN stack alongside SNA/DECnet; precursor ideas to modern networking.

Security

Acronym	Meaning	Example
2FA	Two-Factor Authentication — two independent proofs of identity.	Password + TOTP device.
ABAC	Attribute-Based Access Control — attribute-driven permissions.	Policies on user/resource attributes.
ACL	Access Control List — list of permissions attached to an object specifying which principals are allowed which operations.	Filesystem/network ACLs granting read/write/execute or allow/deny rules.
AES	Advanced Encryption Standard — widely used symmetric block cipher (Rijndael) with 128‑bit blocks and 128/192/256‑bit keys.	AES‑GCM for TLS and at‑rest encryption.
BYOD	Bring Your Own Device — policy allowing use of personal devices for work, requiring security controls and management.	Enforce MDM, device compliance, and conditional access for email/apps.
BYOK	Bring Your Own Key — customer-managed encryption keys used with a cloud provider’s services instead of provider‑managed keys.	Store CMKs in KMS/HSM; configure services to use them; rotate regularly.
CA	Certificate Authority — issues digital certificates (X.509).	Let's Encrypt TLS certs.
CFI	Control-Flow Integrity — restricts indirect branches/returns to valid targets to thwart code‑reuse attacks (ROP/JOP).	LLVM/Clang CFI, Intel CET/IBT, ARM Pointer Authentication (PAC) harden control flow.
CORS	Cross-Origin Resource Sharing — control cross-site requests.	Allow specific origins/headers.
CSP	Content Security Policy — control resource loading; mitigate XSS.	default-src 'self'.
CSRF	Cross-Site Request Forgery — unintended actions by a victim.	CSRF tokens, same-site cookies.
CVE	Common Vulnerabilities and Exposures — public identifier for disclosed security issues.	CVE-2024-XXXXX referenced in advisories and patches.
DAST	Dynamic App Security Testing — test running apps.	Zap/Burp scans.
DDoS	Distributed Denial of Service — many-source DoS.	Botnet floods traffic.
DKIM	DomainKeys Identified Mail — cryptographic email authentication using domain-signed headers.	Receivers verify DKIM-Signature with the sender's DNS key.
DMARC	Domain-based Message Authentication, Reporting, and Conformance — email authentication policy leveraging SPF and DKIM with alignment and reporting.	Publish v=DMARC1; p=quarantine; rua=mailto:dmarc@example.com.
DoS	Denial of Service — make a service unavailable.	Single-source flood.
DRM	Digital Rights Management — technologies to control access, copying, and usage of digital content via encryption and licensing.	Browser EME with Widevine/PlayReady; app checks license server before playback.
GPG	GNU Privacy Guard — OpenPGP implementation.	gpg --sign --encrypt file.
HMAC	Hash-based Message Authentication Code — keyed hash for message integrity and authenticity.	HMAC‑SHA256 for API request signing; JWT HS256.
HSM	Hardware Security Module — tamper‑resistant hardware appliance or cloud service for secure key generation, storage, and cryptographic operations with strong access controls and auditing.	Use an HSM/KMS to generate and store TLS/CA private keys; perform signing inside the module.
HSTS	HTTP Strict Transport Security — force HTTPS for a period.	Strict-Transport-Security header.
IAM	Identity and Access Management — users/roles/permissions.	Cloud IAM policies.
IDS	Intrusion Detection System — monitors networks/hosts for malicious activity or policy violations, generating alerts for investigation.	Network IDS like Zeek/Snort; host IDS like OSSEC/Wazuh; alert to SIEM.
IPS	Intrusion Prevention System — inline security control that inspects traffic/events and can automatically block or remediate detected threats.	IPS mode in next‑gen firewalls; Snort/Suricata inline dropping malicious packets.
JWT	JSON Web Token — compact auth/claims token.	Authorization: Bearer <jwt>.
MAC	Message Authentication Code — short, fixed-length tag produced from a message and secret key that enables verification of message integrity and authenticity.	Compute an AES-CMAC or HMAC-SHA256 over API payloads; receivers recompute the MAC to detect tampering.
MDM	Mobile Device Management — administer and secure mobile/end-user devices via policies, enrollment, and remote actions.	Enforce passcodes, disk encryption, app whitelists; remote wipe on loss.
MFA	Multi-Factor Authentication — 2+ factors.	Password + hardware key.
MITM	Man-In-The-Middle — intercept/alter comms.	Rogue Wi-Fi AP sniffing.
mTLS	Mutual TLS — both client and server present certificates.	Service-to-service auth in meshes.
NX	No-eXecute bit — CPU feature that marks memory pages as non-executable to prevent code execution from data segments like the stack and heap.	OS sets the NX bit on the stack to mitigate buffer overflows; also known as DEP/XD/W^X.
OAuth	Delegated authorization protocol.	Access token for API calls.
OIDC	OpenID Connect — identity layer over OAuth 2.0.	ID token for login.
OTP	One-Time Password — short‑lived code used for authentication; delivered or generated per login.	App‑generated TOTP/HOTP codes; avoid SMS OTP when possible.
PGP	Pretty Good Privacy — encryption/signing format.	Email encryption/signing.
PKCS	Public-Key Cryptography Standards — RSA-led standards defining formats and algorithms used in public-key crypto.	PKCS #1 (RSA), #7/CMS (cryptographic messages), #8 (private keys), #12 (PFX/P12), #5 (PBES), #10 (CSR).
PKI	Public Key Infrastructure — system of CAs, certs, keys, and policies.	Issue and validate X.509 certs.
PoLP	Principle of Least Privilege — grant only the minimum permissions necessary for a user or system to perform its function.	IAM roles with narrowly scoped permissions; run services as non-root users.
RBAC	Role-Based Access Control — role-granted permissions.	Admin/Editor/Viewer roles.
RCE	Remote Code Execution — run arbitrary code remotely.	Deserialization exploit.
ROP	Return-Oriented Programming — code reuse attack that chains existing instruction sequences ("gadgets") ending in ret to execute arbitrary code, bypassing DEP/NX.	Chain ROP gadgets from loaded libraries to call mprotect and make the stack executable.
RSA	Rivest–Shamir–Adleman — widely used public‑key cryptosystem for encryption and signatures.	2048‑bit RSA keys; RSA‑PKCS#1 signatures; TLS certs.
SAM	Security Accounts Manager — the database in Windows that stores user passwords (as hashes) and security principals.	The SAM file (%SystemRoot%/system32/config/SAM); lsass.exe protects it.
SAST	Static App Security Testing — analyze code/binaries.	SAST pipeline checks.
SBOM	Software Bill of Materials — inventory of components, dependencies, and versions in software artifacts for transparency and vulnerability management.	Generate CycloneDX/SPDX SBOMs in CI; scan against CVEs.
SFI	Software Fault Isolation — security technique that sandboxes untrusted code by rewriting its machine code to prevent it from accessing memory or calling functions outside its designated region.	Google Native Client (NaCl) uses SFI to safely run native code in the browser.
SHA	Secure Hash Algorithm — family of cryptographic hash functions (SHA‑2/256/512; SHA‑3/Keccak).	TLS cert signatures, file integrity checks; Git moving from SHA‑1 to SHA‑256.
SPF	Sender Policy Framework — DNS-based mechanism to authorize mail servers for a domain.	v=spf1 ip4:203.0.113.0/24 -all record.
SQLi	SQL Injection — inject SQL via input.	Parameterized queries prevent it.
SSH	Secure Shell — encrypted remote login/exec.	ssh user@host.
SSO	Single Sign-On — authenticate once, access many apps.	SAML/OIDC-based SSO.
SSRF	Server-Side Request Forgery — trick server to make requests.	Block metadata endpoints.
TLS	Transport Layer Security — secure comms.	HTTPS uses TLS.
TOTP	Time-Based One-Time Password — time-synced one-time codes.	Authenticator app 6-digit codes.
XSRF	Alternate name for CSRF in some frameworks.	Angular XSRF-TOKEN cookie/header.
XSS	Cross-Site Scripting — script injection into pages.	Output encoding, CSP.
Legacy
MD5	Message Digest Algorithm 5 — legacy 128-bit cryptographic hash function; cryptographically broken (collisions) and unsuitable for security, but still used for checksums.	md5sum file.iso to verify integrity; avoid for passwords/signatures.
NTLM	NT LAN Manager — a legacy Microsoft authentication protocol suite, superseded by Kerberos.	Windows workgroup authentication; fallback when Kerberos is unavailable.
RACF	Resource Access Control Facility — the primary security system on IBM mainframes (z/OS), controlling access to datasets, applications, and system resources.	Define user profiles and grant dataset access with RACF commands.
Historical
SSL	Secure Sockets Layer — legacy to TLS.	Deprecated; use TLS.

Privacy

Acronym	Meaning	Example
CCPA	California Consumer Privacy Act — US privacy law granting rights to access, delete, and opt out of sale of personal data.	Add Do Not Sell link; handle access/deletion requests.
CPRA	California Privacy Rights Act — amends/expands CCPA with new rights (correction), sensitive data category, and the CPPA regulator.	Honor opt-out for sharing; handle sensitive PI with limits.
DSAR	Data Subject Access Request — request by an individual to access, correct, delete, or obtain a copy of their personal data.	Process access/erasure/portability requests within statutory timelines.
GDPR	General Data Protection Regulation — EU law governing personal data protection, rights, and obligations.	Lawful basis, DPO, DPIA; data subject rights (access/erasure/portability).
HIPAA	Health Insurance Portability and Accountability Act — US law setting privacy/security standards for protected health information (PHI).	Covered entities sign BAAs; apply the HIPAA Privacy/Security Rules.
PII	Personally Identifiable Information — data that can identify an individual; subject to privacy laws and safeguards.	Names, emails, SSNs; apply minimization, masking, and access controls.

Infrastructure

Acronym	Meaning	Example
AD	Active Directory — Microsoft identity directory service.	Centralized auth/authorization.
CDN	Content Delivery Network — globally distributed cache.	Faster static asset delivery.
DNS	Domain Name System — resolve names to IPs.	A, AAAA, CNAME records.
DNSSEC	Domain Name System Security Extensions — adds origin authentication and data integrity to DNS using digital signatures (RRSIG) validated via a chain of trust from signed zones and DS records.	Sign zones with ZSK/KSK; validators check RRSIGs and DS chain from the root; prevents cache poisoning/spoofing.
FaaS	Function as a Service — serverless functions.	AWS Lambda handlers.
FQDN	Fully Qualified Domain Name — complete, absolute domain name that specifies all labels up to the root.	host1.db.eu-west.example.com. (trailing dot optional in practice).
HPC	High-Performance Computing — parallel, large-scale compute using clusters/supercomputers for scientific/engineering workloads.	Run MPI/Slurm jobs on a GPU/CPU cluster with InfiniBand.
IaaS	Infrastructure as a Service — virtual compute/storage/network.	EC2/Compute Engine.
IaC	Infrastructure as Code — manage infrastructure with code and VCS.	Use Terraform to provision cloud resources via PRs.
IoT	Internet of Things — networked embedded devices and sensors that collect data and interact with the physical world.	MQTT devices sending telemetry to an IoT hub.
K8S	Kubernetes — container orchestration.	kubectl get pods.
KMS	Key Management Service — managed key storage and cryptographic operations.	AWS KMS for envelope encryption and key rotation.
KVM	Kernel-based Virtual Machine — Linux kernel virtualization enabling VMs with hardware acceleration via KVM modules.	Run QEMU with KVM for near-native performance; manage with libvirt/virt-manager.
LB	Load Balancer — distributes traffic across multiple backends for scalability and resilience.	AWS ALB/NLB, HAProxy/Nginx with health checks and stickiness.
LXC	Linux Containers — OS-level virtualization using cgroups/namespaces to isolate processes.	Run lightweight containers without a separate kernel per instance.
MPI	Message Passing Interface — standardized API for distributed-memory parallel programming using processes that communicate via messages.	Launch ranks with mpirun (OpenMPI/MPICH); use collectives like MPI_Bcast/MPI_Reduce.
NAS	Network-Attached Storage — dedicated file storage accessible over a network.	Home/SMB NAS appliances exposing NFS/SMB shares.
OCI	Open Container Initiative — specs for container images and runtimes.	OCI Image format and OCI Runtime (runc).
PaaS	Platform as a Service — deploy apps without infra mgmt.	Heroku, App Engine.
QEMU	Quick EMUlator — open-source machine emulator and virtualizer supporting full-system emulation and hardware-accelerated virtualization across many architectures.	Boot ARM or RISC-V guests with qemu-system-*; pair with KVM for x86 virtualization on Linux hosts.
SaaS	Software as a Service — subscription-based software.	Hosted CRM/Email.
SAN	Storage Area Network — high-speed network providing block-level storage access to servers.	Fibre Channel/iSCSI SAN for shared volumes.
SIMH	Simulator for Historical Computers — open-source emulator suite for classic minicomputers/mainframes (PDP-11, VAX, IBM 1401, etc.), preserving vintage software environments.	Boot a PDP-11 running RT-11/RSX or a VAX/VMS system image for retrocomputing and software archaeology.
TCG	Tiny Code Generator — QEMU's dynamic binary translation engine that recompiles guest CPU instructions into host machine code at runtime when hardware acceleration isn't available.	Run QEMU in pure emulation mode; TCG translates ARM guest opcodes to x86 host instructions on the fly.
UPS	Uninterruptible Power Supply — device providing battery-backed power to keep equipment running through short outages and allow graceful shutdown.	Rack UPS for servers/network gear; runtime and VA/W ratings.
VM	Virtual Machine — emulated hardware environment to run OS instances.	KVM/Hyper-V VMs for isolation.
VPC	Virtual Private Cloud — isolated virtual network.	Subnets, route tables, SGs.
VPN	Virtual Private Network — secure tunnel.	Site-to-site/client VPN.

Hardware (Architecture)

Acronym	Meaning	Example
AMD64	64-bit x86 architecture introduced by AMD (aka x86-64, adopted by Intel as Intel 64) extending IA-32 with 64-bit registers, more general-purpose registers, and long mode.	Build for x86_64/amd64; Linux System V AMD64 ABI; Windows x64 with WOW64 for 32-bit apps.
ARM	Advanced RISC Machines — 32-bit RISC architecture (AArch32) originating from Acorn, spanning ARMv1-v7 cores widely used in mobile, embedded, and microcontroller systems.	Cross-compile for armv7/armhf; run 32-bit ARM Linux on Raspberry Pi models or Cortex-M firmware.
ARM64	64-bit ARM architecture (aka AArch64, ARMv8-A and later) with a new instruction set and execution state distinct from 32-bit ARM (AArch32).	Build for arm64/aarch64; Apple Silicon Macs, AWS Graviton/Neoverse servers, Android flagship SoCs.
ASIC	Application-Specific Integrated Circuit — a chip customized for a particular use, rather than for general-purpose use like a CPU.	Bitcoin mining ASICs; Google TPU for machine learning.
CHERI	Capability Hardware Enhanced RISC Instructions — architectural extensions that add tagged, unforgeable capabilities to enforce fine‑grained memory safety and compartmentalization.	CHERI‑RISC‑V/MIPS; pointers carry bounds/permissions; safer C/C++ and sandboxing.
CISC	Complex Instruction Set Computer — CPU design approach featuring larger, more complex, and variable‑length instructions, often implemented with microcode.	x86/x86‑64 architectures; REP MOVS, string ops, rich addressing modes.
CUDA	Compute Unified Device Architecture — NVIDIA's parallel computing platform and programming model for GPUs.	Launch kernels in CUDA C++; PyTorch/TensorFlow GPU ops.
EM64T	Extended Memory 64 Technology — Intel’s original branding for its AMD64‑compatible 64‑bit x86 implementation, now marketed as Intel 64.	Intel Core/Xeon CPUs report Intel 64; target x86_64 in toolchains.
IA-32	32‑bit Intel architecture — the classic 32‑bit x86 ISA (i386 and successors) with protected mode, paging, and SSE-era extensions; predecessor to x86‑64.	Build for x86/i386/i686; 32‑bit OSes/apps, WOW64 on Windows x64, multilib on Linux.
ISA	Instruction Set Architecture — contract describing a CPU’s instructions, registers, memory model, and privilege levels; distinct from microarchitecture.	x86‑64, ARMv8‑A; RISC‑V RV64GC with optional extensions.
MIPS	Microprocessor without Interlocked Pipeline Stages — classic RISC architecture used in embedded systems, networking gear, and historically in workstations/servers.	MIPS32/MIPS64 in routers and embedded devices; historical SGI workstations/IRIX.
NUMA	Non-Uniform Memory Access — architecture where memory access latency and bandwidth vary depending on whether memory is local to a CPU socket/node or remote.	Pin threads and allocate memory per NUMA node (e.g., numactl) to reduce cross-socket traffic.
PA-RISC	Precision Architecture RISC — Hewlett‑Packard’s RISC architecture used in HP 9000 servers/workstations, largely superseded by Itanium and then x86‑64.	HP‑UX on PA‑RISC systems (e.g., PA‑8700/8900); historical HP 9000 platforms.
POWER	IBM Performance Optimization With Enhanced RISC — IBM’s RISC architecture family used in servers/workstations (POWER4+), distinct but related to the PowerPC lineage.	IBM Power Systems running AIX/IBM i/Linux; POWER9/POWER10 CPUs.
PPC	PowerPC — RISC CPU architecture developed by the AIM alliance (Apple–IBM–Motorola), used in desktops historically and widely in embedded/console systems.	PowerPC 32/64‑bit (POWER/PowerPC); GameCube/Wii/PS3; embedded/controllers.
RISC	Reduced Instruction Set Computer — CPU design philosophy emphasizing a small, simple instruction set and efficient pipelines.	ARM and RISC-V architectures.
RISC-V	Open standard RISC instruction set architecture with modular extensions (e.g., I/M/A/F/D/V) and 32/64/128‑bit variants (RV32/64/128); free to implement without licensing.	Microcontrollers to servers; Linux on RV64GC; chips from SiFive, Andes; SBCs and accelerators.
SMP	Symmetric Multiprocessing — architecture where multiple identical CPUs/cores share the same memory and OS, enabling parallel execution of threads/processes.	Multi-core x86/ARM systems; OS scheduler runs threads across cores with shared memory.
SPARC	Scalable Processor ARChitecture — RISC CPU architecture originally developed by Sun Microsystems, widely used in servers/workstations and embedded systems.	SPARC V8/V9 (32/64‑bit); UltraSPARC/Oracle SPARC running Solaris/illumos.
X86-64	Generic name for the 64‑bit x86 ISA (defined by AMD as AMD64 and implemented by Intel as Intel 64/EM64T); adds 64‑bit mode and more registers over IA‑32.	Build for x86_64; 64‑bit OSes and apps on AMD/Intel processors.
Historical
AT	Advanced Technology — the IBM PC/AT was the successor to the XT, introducing the 16-bit ISA bus, the 286 processor, and the AT keyboard connector.	The AT form factor and motherboard design influenced PCs for years.
CD-i	Compact Disc Interactive — a multimedia CD player and platform developed by Philips and Sony.	Known for its games and educational titles in the early 1990s.
IA-64	Intel Itanium architecture — 64‑bit EPIC (Explicitly Parallel Instruction Computing) ISA developed by Intel/HP; distinct from x86/x86‑64 and now discontinued.	Itanium servers/workstations running HP‑UX, OpenVMS, and legacy Windows Server for Itanium‑based systems.
MSX	Machines with Software eXchangeability — a standardized home computer architecture from the 1980s.	Popular in Japan and Europe; Konami games on MSX.
PDP	Programmed Data Processor — DEC minicomputer line before VAX.	PDP‑8, PDP‑11 systems.
VAX	Virtual Address eXtension — DEC 32‑bit minicomputer architecture.	VAX/VMS systems in universities and industry.
XT	Extended Technology — the IBM PC XT was an early version of the PC that included a hard drive.	The 8-bit bus architecture of the PC/XT.

Hardware (CPU / General)

Acronym	Meaning	Example
ALU	Arithmetic Logic Unit — digital circuit in the CPU that performs integer arithmetic and bitwise operations.	Add, subtract, AND/OR/XOR, shifts/rotates executed by the ALU pipelines.
AP	Application Processor — any non‑bootstrap CPU core in an SMP system that is brought online by the BSP to run the OS scheduler and workloads.	OS sends INIT/SIPI to start APs after BSP init; threads scheduled across APs.
BSP	Bootstrap Processor — on multi-processor systems (e.g., x86 SMP), the primary CPU core that starts executing firmware/boot code and brings up the OS, which then initializes the remaining cores as Application Processors (APs).	Firmware runs on the BSP first; OS sends INIT/SIPI to start APs.
CPU	Central Processing Unit — main processor that executes instructions.	x86-64 CPUs with multiple cores/threads and SIMD.
FPU	Floating Point Unit — hardware for floating-point arithmetic.	IEEE 754 operations, SIMD extensions.
L1/L2/L3	Level 1/2/3 Cache — hierarchical caches in a CPU that store frequently accessed data to reduce latency to main memory.	L1 is fastest/smallest (per-core I/D); L2 is larger (per-core); L3 is largest (shared).
MMU	Memory Management Unit — hardware for virtual memory and address translation.	x86-64 paging with TLBs.
NMI	Non-Maskable Interrupt — high-priority hardware interrupt that cannot be disabled by normal interrupt masking, used for critical fault or watchdog conditions.	Watchdog parity/ECC errors trigger NMI; OS NMI handler logs/diagnoses hangs.
SIMD	Single Instruction, Multiple Data — vector parallelism executing the same instruction across multiple data lanes.	SSE/AVX on x86, NEON on ARM.
TLB	Translation Lookaside Buffer — small cache of virtual→physical address translations used by the MMU.	TLB hits speed up paging; TLB flush on context switch.

Hardware (CPU / ARM)

Acronym	Meaning	Example
EL0/1/2/3	Exception Levels — ARMv8 privilege levels: EL0 (unprivileged), EL1 (OS kernel), EL2 (hypervisor), EL3 (secure monitor).	User apps run at EL0; the kernel at EL1; KVM at EL2.
GIC	Generic Interrupt Controller — standard ARM architecture for managing interrupts, routing them from peripherals to CPU cores.	GICv2/v3/v4; the ARM equivalent of x86's APIC.
NEON	ARM's advanced SIMD (Single Instruction, Multiple Data) architecture extension for accelerating multimedia and signal processing.	NEON intrinsics for video encoding; equivalent to x86 SSE/AVX.
SVE	Scalable Vector Extension — next-generation SIMD instruction set for ARM AArch64, designed for HPC with vector-length agnostic programming.	High-performance computing workloads on ARM servers.

Hardware (CPU / x86)

Acronym	Meaning	Example
AMX	Advanced Matrix Extensions — x86 instruction set extensions providing tiled matrix operations accelerated in hardware.	Intel AMX for deep‑learning inference/training (tile registers, TMUL).
APIC	Advanced Programmable Interrupt Controller — modern local/IO APICs providing scalable interrupt delivery in SMP systems.	LAPIC per core and IOAPIC for external IRQs on x86.
AVX	Advanced Vector Extensions — x86 SIMD instruction set extensions for wide vector operations (256/512-bit in AVX/AVX-512).	AVX2 for integer ops; AVX-512 for HPC workloads.
SSE	Streaming SIMD Extensions — x86 SIMD instruction set extensions for parallel vector operations.	SSE2/SSE4 intrinsics; compiler autovectorization for math/graphics.
VMX	Virtual Machine Extensions — Intel x86 virtualization extensions (VT‑x) that add CPU modes/instructions (VMX root/non‑root, VMXON/VMXOFF, VMLAUNCH/VMRESUME) and a VMCS for hardware‑assisted virtualization.	Enable VT‑x in firmware; KVM/Hyper‑V/VMware use VMX to run guests with hardware assist.
xAPIC	Extended APIC — the default operational mode for the modern x86 APIC, using MMIO for register access.	The OS maps the LAPIC's MMIO region to send IPIs and manage local interrupts.
Historical
MMX	MultiMedia eXtensions — early x86 SIMD instruction set for integer vector operations.	Legacy MMX ops predating SSE on Pentium-era CPUs.

Hardware (Memory)

Acronym	Meaning	Example
DDR	Double Data Rate — class of synchronous DRAM that transfers data on both clock edges for higher bandwidth.	DDR4/DDR5 SDRAM in modern systems.
DIMM	Dual Inline Memory Module — standardized memory module form factor for SDRAM.	288‑pin DDR4/DDR5 DIMMs.
DRAM	Dynamic Random Access Memory — volatile memory storing bits in capacitors that require periodic refresh.	Main system memory (SDRAM/DDR).
ECC	Error-Correcting Code memory — memory modules/chipsets that detect and correct single‑bit errors (and detect some multi‑bit errors) to improve reliability.	ECC UDIMMs/RDIMMs in servers/workstations; machine check logs corrected errors.
EEPROM	Electrically Erasable Programmable Read-Only Memory — non-volatile memory that can be electrically erased and reprogrammed at the byte/page level; used for small configuration storage and microcontroller data.	I²C/SPI EEPROMs (24xx/25xx series); MCU calibration data; distinct from flash (block erase).
GDDR	Graphics Double Data Rate — high‑bandwidth memory variants optimized for GPUs and graphics workloads.	GDDR6/GDDR6X on modern GPUs; wide buses and high data rates.
HBM	High Bandwidth Memory — stacked memory connected via wide interfaces on‑package for very high bandwidth and energy efficiency.	HBM2/HBM3 on AI/ML accelerators and high‑end GPUs.
LPDDR	Low-Power DDR — mobile/embedded DRAM optimized for low power with deep power states and wide IO at low voltage.	LPDDR4/4X/5/5X in smartphones, tablets, ultrabooks, and SoCs.
NVRAM	Non-Volatile RAM — memory that retains data without power; implemented via flash, EEPROM, or battery‑backed SRAM; often stores firmware variables/settings.	UEFI variables in NVRAM; macOS NVRAM for boot args and device settings.
RAM	Random Access Memory — volatile memory used for working data and code.	DDR4/DDR5 DIMMs.
ROM	Read-Only Memory — non-volatile memory storing firmware or static data.	Boot ROM, option ROMs.
SDRAM	Synchronous Dynamic Random Access Memory — DRAM synchronized with the system clock, enabling pipelined access and higher throughput versus asynchronous DRAM.	PC100/PC133 SDRAM; basis for modern DDR (DDR/DDR2/3/4/5).
SO-DIMM	Small Outline Dual Inline Memory Module — compact memory module form factor used in laptops and small form-factor systems; electrically similar to DIMMs but physically smaller and not interchangeable.	DDR4/DDR5 SO‑DIMMs in laptops/NUCs; shorter modules with different keying.
SRAM	Static Random Access Memory — volatile memory using flip-flops; fast and does not need refresh.	CPU caches (L1/L2/L3) implemented with SRAM.
Historical
EDO	Extended Data Out DRAM — improved asynchronous DRAM that allows the data output to remain valid longer, enabling slightly higher performance than FPM before SDRAM became mainstream.	Mid‑1990s 486/Pentium systems with EDO SIMMs; replaced by SDRAM.
EPROM	Erasable Programmable Read-Only Memory — UV-erasable ROM chips with a quartz window; erased under UV light and reprogrammed with a programmer.	27xx-series EPROMs in retro computers/arcade boards; UV eraser tools.
FPM	Fast Page Mode DRAM — asynchronous DRAM access mode that speeds up accesses within the same row/page compared to plain DRAM; predecessor to EDO and SDRAM.	Early 1990s SIMM modules using FPM; superseded by EDO/SDRAM.
PROM	Programmable Read-Only Memory — one-time programmable ROM that can be programmed once after manufacturing and cannot be erased.	82S/27S series PROMs used for microcode/firmware; fuse/antifuse technologies.
RDRAM	Rambus DRAM — high‑bandwidth DRAM technology from Rambus used with RIMM modules and a packetized, narrow bus; briefly mainstream on Pentium 4 before being displaced by DDR SDRAM.	RIMM modules in Intel i850/i850E chipsets; now obsolete in favor of DDR/DDR2+.
RIMM	Rambus Inline Memory Module — module form factor for RDRAM with continuity requirements (CRIMMs in empty slots) and heat spreaders; used briefly in early‑2000s PCs/servers.	Populate paired RIMMs on i850 boards; install CRIMMs in unused slots; now obsolete.
SIMM	Single Inline Memory Module — older memory module form factor with a single set of contacts; used with FPM/EDO/early SDRAM.	30‑pin/72‑pin SIMMs on 386/486/Pentium-era systems.

Hardware (Buses & Interfaces)

Acronym	Meaning	Example
AHB	Advanced High-performance Bus — an AMBA bus protocol for connecting lower-performance peripherals.	Part of the on-chip bus fabric in an ARM SoC.
AMBA	Advanced Microcontroller Bus Architecture — a family of on-chip interconnect specifications for connecting functional blocks in an SoC.	AMBA protocols include AXI, AHB, and APB.
APB	Advanced Peripheral Bus — a low-bandwidth AMBA bus protocol for simple peripherals.	Connecting UARTs, GPIO, and timers in an SoC.
AXI	Advanced eXtensible Interface — a high-performance AMBA bus protocol for demanding components like CPUs, GPUs, and memory controllers.	The main high-speed bus in a modern ARM SoC.
CCIX	Cache Coherent Interconnect for Accelerators — an industry standard for coherent interconnects between processors and accelerators.	Connecting FPGAs or GPUs to an ARM server CPU.
CMN	Coherent Mesh Network — ARM's high-performance mesh interconnect for connecting components within an SoC and between multiple SoCs.	The socket-to-socket interconnect in multi-socket ARM servers.
DMI	Direct Media Interface — Intel's proprietary link between a CPU and the Platform Controller Hub (PCH).	DMI 3.0/4.0 providing bandwidth for peripherals connected to the PCH.
GPIO	General-Purpose Input/Output — configurable digital pins on microcontrollers/SoCs used for reading inputs and driving outputs; often support pull‑ups/downs and interrupts.	Toggle Raspberry Pi GPIO with libgpiod; configure pin mode and edge interrupts.
HBA	Host Bus Adapter — adapter that connects a host system to storage or network devices over a high‑speed bus/fabric (e.g., SAS, Fibre Channel).	FC/SAS HBAs in servers to attach SAN/storage arrays; visible via lspci.
HCI	Host Controller Interface — standardized command/event interface between a host stack and a hardware controller (notably in Bluetooth; also USB xHCI).	Capture Bluetooth HCI packets with btmon; interact via UART/USB HCI.
I2C	Inter-Integrated Circuit — a synchronous, multi-controller, multi-peripheral serial bus used for attaching low-speed peripherals to a motherboard or embedded system.	Connect sensors/EEPROMs to a microcontroller (SDA/SCL lines).
JTAG	Joint Test Action Group — industry standard for on-chip debugging, programming, and testing of integrated circuits.	Use a JTAG debugger to halt a CPU, inspect registers, and flash firmware.
MIDI	Musical Instrument Digital Interface — standard protocol/interface for transmitting musical performance data between instruments, controllers, and computers.	5‑pin DIN or USB‑MIDI; Note On/Off, Control Change; DAW controlling a synth.
PCI	Peripheral Component Interconnect — hardware bus standard for attaching peripherals.	PCI devices enumerated by bus/device/function.
PCIe	PCI Express — high-speed serial successor to PCI with lanes and links.	x16 GPU slot; NVMe drives over PCIe.
PS/2	Personal System/2 — legacy Mini‑DIN interface for keyboards and mice on PCs.	PS/2 keyboard/mouse ports on motherboards/KVMs; supports NKRO without USB polling.
SPI	Serial Peripheral Interface — synchronous serial bus with master/slave (controller/peripheral) and separate data lines for full-duplex transfers.	Connect sensors/flash to microcontrollers (MOSI/MISO/SCLK/CS); higher speed than I²C.
UART	Universal Asynchronous Receiver-Transmitter — hardware for serial communication using asynchronous framing (start/stop bits) over TTL/RS-232 levels.	Debug console on microcontrollers; /dev/ttyS*//dev/ttyUSB*; 115200 8N1.
UPI	Ultra Path Interconnect — Intel's current point-to-point processor interconnect for server CPUs, successor to QPI.	High-speed link between sockets on multi-processor Xeon systems.
USB	Universal Serial Bus — standard for cables and connectors between computers and peripherals.	USB 3.x devices; HID, storage, and serial classes.
Legacy
COM	Serial COM port — PC designation for RS‑232 serial interfaces (COM1/COM2/...), typically provided by 16550‑class UARTs on DB‑9 connectors.	Connect via null‑modem/USB‑serial; Windows COM3:; Linux /dev/ttyS0 serial consoles.
LPC	Low Pin Count — a bus used on PC-compatible motherboards to connect low-bandwidth devices to the southbridge.	Connects the Super I/O chip, BIOS ROM, and TPM.
QPI	QuickPath Interconnect — Intel's point-to-point processor interconnect that replaced the FSB; superseded by UPI.	High-speed link between CPU and I/O hub on Nehalem/Sandy Bridge-E systems.
Historical
BNC	Bayonet Neill-Concelman — coaxial RF connector with a quarter-turn bayonet lock, historically common for thin Ethernet, video, and instrumentation signals.	10BASE2 networks daisy-chained via BNC T-connectors with 50-ohm terminators; oscilloscopes and signal generators using BNC jacks.
EISA	Extended Industry Standard Architecture — 32-bit ISA-compatible bus developed by a consortium as an open alternative to MCA; supported bus mastering and IRQ sharing.	Server-class 486 systems with EISA expansion cards; later replaced by PCI.
FSB	Front-Side Bus — the main interface between the CPU and the northbridge in older PC architectures, superseded by on-chip memory controllers and point-to-point interconnects.	Pentium 4 on an 800MHz FSB; overclocking by raising the FSB speed.
ISA	Industry Standard Architecture — legacy 8/16‑bit PC expansion bus.	Sound/IO cards on 286/386 era PCs.
LPT	Line Printer port — PC parallel printer interface (Centronics/IEEE 1284), addressed as LPT1/LPT2; largely obsolete.	Parallel printers and hardware dongles; DB‑25 connectors; IEEE 1284 SPP/EPP/ECP modes.
MCA	Micro Channel Architecture — IBM's proprietary 32‑bit bus introduced with PS/2 systems as a successor to ISA; offered bus mastering and improved throughput but lacked industry adoption.	IBM PS/2 expansion cards; supplanted by EISA/PCI.
PCMCIA	Personal Computer Memory Card International Association — the standard for laptop expansion cards (e.g., modems, network cards) before USB and ExpressCard.	Also known as PC Card; Type I/II/III cards.
Q-BUS	DEC Q‑bus — asynchronous multiplexed address/data bus used in later PDP‑11 and early MicroVAX systems; lower-cost successor to Unibus with fewer signals.	Q‑bus backplanes/peripherals in PDP‑11/23 and MicroVAX; legacy DEC minicomputers.
Unibus	DEC Unibus — early synchronous shared backplane bus interconnecting CPU, memory, and peripherals in PDP‑11 systems; predecessor to Q‑bus.	PDP‑11 Unibus backplanes/peripherals; historical DEC minicomputers.
VLB	VESA Local Bus — high‑speed local bus before PCI.	486 motherboards with VLB video/IO cards.
VME	VMEbus (Versa Module Europa) — parallel backplane bus standard (IEEE 1014) widely used in embedded/industrial systems with Eurocard form factors (3U/6U) and modular CPU/I/O cards.	VME chassis in telecom, industrial control, and defense; CPU cards and I/O modules on a shared backplane.

Hardware (Storage)

Acronym	Meaning	Example
AHCI	Advanced Host Controller Interface — standard programming interface for SATA host controllers enabling features like NCQ, hot-plug, and native command queuing.	OS uses the AHCI driver; set SATA mode to AHCI in firmware for modern OS installs.
GPT	GUID Partition Table — modern disk partitioning scheme that supports large disks and many partitions, part of the UEFI standard.	Disks initialized with GPT instead of legacy MBR.
HDD	Hard Disk Drive — magnetic storage device with spinning platters and moving heads.	3.5"/2.5" SATA HDDs for bulk storage; higher latency than SSDs.
LBA	Logical Block Addressing — linear addressing scheme for block devices that replaces legacy CHS (Cylinder/Head/Sector) geometry.	512‑byte/4K sectors addressed by LBA; used by SATA/SCSI/NVMe.
LTO	Linear Tape-Open — open tape storage format for data backup/archive with generational roadmap (LTO‑1..LTO‑9), high capacity, and LTFS support.	LTO‑8/LTO‑9 tape drives/libraries in enterprise backups; use LTFS for file‑like access.
LUN	Logical Unit Number — identifier addressing a logical unit (virtual disk) within a SCSI/iSCSI/Fibre Channel target, used for mapping storage to hosts.	Present LUNs from a SAN array to servers; host multipath to the same LUN.
NCQ	Native Command Queuing — SATA feature allowing a drive to accept and reorder multiple outstanding requests to optimize head movement and throughput.	AHCI/SATA HDDs/SSDs improving random I/O by reordering commands.
NVMe	Non-Volatile Memory Express — interface protocol for SSDs over PCIe.	M.2 NVMe SSD with high IOPS/low latency.
RAID	Redundant Array of Independent Disks — combine multiple drives for redundancy and/or performance.	RAID 1 mirroring; RAID 5 parity; RAID 10 stripe+mirror.
SAS	Serial Attached SCSI — point‑to‑point serial interface for enterprise storage.	12Gb/s SAS HDDs/SSDs; SAS expanders/backplanes.
SATA	Serial ATA — interface for connecting storage devices.	2.5" SATA SSDs and HDDs.
SD	Secure Digital — flash memory card format with variants (SD/SDHC/SDXC) commonly used in portable devices; typically formatted with FAT32 or exFAT.	Cameras, handheld consoles, and phones; microSD cards with adapters.
SMART	Self-Monitoring, Analysis and Reporting Technology — monitoring system in disk drives to detect and report on indicators of drive reliability.	smartctl to read SMART data and predict drive failure.
SSD	Solid-State Drive — storage device using flash memory (no moving parts), offering low latency and high throughput.	NVMe SSDs for fast boot and build times.
Legacy
EIDE	Enhanced IDE — extensions to IDE/PATA.	Support for larger drives and ATAPI.
IDE/PATA	Integrated Drive Electronics / Parallel ATA — legacy parallel disk interface.	40/80‑wire ribbon cables for HDD/optical drives.
MBR	Master Boot Record — legacy partitioning scheme and first 512 bytes of a disk containing boot code and a partition table.	BIOS boots from MBR; up to 4 primary partitions or extended/logical.
UDMA	Ultra Direct Memory Access — ATA/IDE DMA transfer modes providing higher throughput and lower CPU usage than PIO; modes UDMA/33/66/100/133 (higher modes require 80‑wire cables).	PATA drive negotiates UDMA/5 (ATA/100); Linux dmesg shows UDMA/133.
WORM	Write Once, Read Many — non‑rewritable archival storage media.	Optical WORM jukeboxes for compliance archives.
Historical
CHS	Cylinder/Head/Sector — legacy disk geometry addressing scheme used by BIOS/MBR era systems; limited capacity and translation quirks.	1024‑cylinder limit; CHS/LBA translation in BIOS; superseded by LBA.
DDS	Digital Data Storage — magnetic tape data storage format derived from DAT (Digital Audio Tape), widely used for backups in the 1990s–2000s (DDS‑1..4, DDS‑DC, DAT72).	DAT/DDS tape drives and media for server/workstation backups; largely obsolete today.
DLT	Digital Linear Tape — half‑inch magnetic tape storage format popular in the 1990s–2000s for enterprise backups; superseded by LTO.	DLT/SDLT drives and media in tape libraries; largely obsolete now.
FDD	Floppy Disk Drive — magnetic removable storage.	5.25" and 3.5" floppies.
MFM	Modified Frequency Modulation — legacy disk encoding scheme.	Early HDDs and floppies using MFM/RLL.
QIC	Quarter-Inch Cartridge — magnetic tape data storage format using 1/4" tape in cartridges; common for backups on PCs/workstations in the 1980s–1990s (e.g., QIC-80/150, Travan).	Tape backup drives and cartridges; largely obsolete today.
RLL	Run Length Limited — denser successor to MFM for magnetic storage.	RLL controllers for higher HDD capacity.
SCSI	Small Computer System Interface — parallel peripheral bus widely used pre‑SATA/USB.	External SCSI disks and scanners on workstations.

Hardware (Video & Displays)

Acronym	Meaning	Example
DP	DisplayPort — digital display interface with high bandwidth, daisy‑chaining via MST, and adaptive sync support.	DP 1.4/2.0 to high‑refresh monitors; USB‑C DP Alt Mode; MST hub.
DPI	Dots Per Inch — measure of print/display resolution; colloquially used for screens though PPI is more precise.	300‑DPI print quality; “Retina” displays around ~220 PPI.
EDID	Extended Display Identification Data — data structure provided by a display to describe its capabilities (e.g., resolution, timings) to a video source.	GPU reads monitor's EDID over DDC to configure the display mode.
GPU	Graphics Processing Unit — highly parallel processor optimized for graphics and compute.	CUDA/OpenCL workloads; 3D rendering.
HD	High Definition — 720p (1280×720) and 1080i/p (1920×1080) resolution classes.	1080p monitor; HD streaming.
HDCP	High-bandwidth Digital Content Protection — copy protection scheme to prevent copying of digital audio/video content as it travels across connections.	HDMI/DisplayPort connections requiring HDCP for protected content playback.
HDMI	High-Definition Multimedia Interface — digital audio/video interface for connecting sources to displays.	HDMI 2.0/2.1 to monitors/TVs; HDCP for protected content.
LCD	Liquid Crystal Display — flat‑panel display technology that uses liquid crystals modulated by a backlight to produce images.	IPS/TN/VA LCD panels; requires LED backlight.
LED	Light‑Emitting Diode — semiconductor light source; in monitors/TVs, often shorthand for LED‑backlit LCDs (not emissive per‑pixel).	Status indicator LEDs; LED‑backlit LCD monitors/TVs.
OLED	Organic Light‑Emitting Diode — emissive display technology where each pixel emits light for high contrast and true blacks.	AMOLED smartphone screens; per‑pixel dimming on TVs/phones.
PPI	Pixels Per Inch — measure of display pixel density; often confused with DPI which is for print.	326‑PPI phone display; ~220‑PPI “Retina” laptop panels.
QHD	Quad High Definition — 2560×1440 (1440p) resolution at 16:9; roughly 4× 720p and about half the pixels of 4K UHD.	27" 1440p monitors; competitive gaming displays.
RGB	Red, Green, Blue — additive color model used in displays and imaging.	sRGB color space; RGB LED subpixels in LCD/OLED panels.
RGBA	Red, Green, Blue, Alpha — RGB color with an additional alpha (opacity) channel for transparency.	CSS rgba(255, 0, 0, 0.5); PNG images with alpha channel.
UHD	Ultra High Definition — 4K UHD (3840×2160) consumer resolution class; sometimes extends to 8K (7680×4320).	4K 2160p TV/monitor; UHD streaming.
VESA	Video Electronics Standards Association — industry group that defines and maintains display and related interface standards.	DisplayHDR, DP standards, EDID/DMT timing standards.
VRAM	Video RAM — memory used by GPUs/display controllers to store framebuffers, textures, and render targets; historically specialized types (e.g., SGRAM, GDDR).	Dedicated GDDR6 on discrete GPUs; shared system memory on iGPUs.
Legacy
SD	Standard Definition — legacy video resolution class around 480i/480p (NTSC) or 576i/576p (PAL), typically 4:3 aspect.	DVD 480p; SDTV broadcast.
SVGA	Super VGA — VESA extensions beyond VGA.	800×600 and higher resolutions.
VGA	Video Graphics Array — de facto PC graphics standard.	640×480 16‑color; mode 13h 320×200×256.
Historical
AGP	Accelerated Graphics Port — dedicated graphics slot pre‑PCIe.	AGP 4×/8× graphics cards.
CGA	Color Graphics Adapter — IBM PC color graphics standard.	320×200 4‑color modes on early PCs.
CRT	Cathode Ray Tube — vacuum tube display technology that steers electron beams across a phosphor‑coated screen to form images.	Legacy CRT monitors/TVs; scanlines, phosphor persistence, high refresh at lower resolutions.
EGA	Enhanced Graphics Adapter — improved IBM graphics adapter.	640×350 16‑color graphics.
MDA	Monochrome Display Adapter — the original text-only video card for the IBM PC.	80x25 character mode with a green or amber phosphor monitor.

Hardware (General)

Acronym	Meaning	Example
ATX	Advanced Technology eXtended — PC motherboard and power supply form factor standard defining board sizes, mounting, I/O shield, and power connectors.	ATX/mATX/ITX cases; 24‑pin ATX, 8‑pin EPS12V, PCIe 6/8‑pin/12VHPWR.
CMOS	Complementary Metal‑Oxide‑Semiconductor — low‑power technology used for chips; in PCs, also refers to the small battery‑backed RAM storing firmware settings.	Replace CMOS battery; clear CMOS to reset BIOS/UEFI settings.
DMA	Direct Memory Access — device-initiated memory transfers without CPU involvement.	NICs use DMA for packet buffers.
FPGA	Field-Programmable Gate Array — reconfigurable semiconductor device consisting of programmable logic blocks and interconnects configured by a bitstream to implement custom digital circuits.	Prototype/accelerate designs; soft CPUs and hardware offload over PCIe; tools like Vivado/Quartus using HDL/RTL.
HID	Human Interface Device — USB device class for human input/output peripherals using structured HID reports.	USB keyboards, mice, gamepads; HID report descriptors parsed by OS.
HPET	High Precision Event Timer — modern hardware timer with multiple high-resolution counters/comparators, providing precise periodic interrupts and timestamps that supersede legacy PIT/RTC timers in PCs.	Program HPET registers via MMIO to drive scheduler ticks, high-resolution timers, or multimedia clocks with microsecond accuracy.
IRQ	Interrupt Request — a hardware signal line used by devices to interrupt the CPU for service.	Timer, keyboard, NIC raise IRQs; OS dispatches to ISRs.
KVM	Keyboard–Video–Mouse switch — hardware device to control multiple computers with a single keyboard, monitor, and mouse.	Toggle between two PCs with a USB/HDMI KVM switch.
MMIO	Memory-Mapped I/O — device registers mapped into the CPU address space for control/status.	Writing to MMIO addresses to control PCIe device registers.
NIC	Network Interface Controller — hardware that connects a computer to a network.	Ethernet adapters; 10/25/40/100GbE NICs with offloads.
OEM	Original Equipment Manufacturer — company that produces components or products that are marketed by another company; also denotes vendor‑specific builds/licenses.	OEM Windows licenses preinstalled on PCs; OEM parts used by system integrators.
PC	Personal Computer — general-purpose computer intended for individual use; commonly refers to IBM‑PC compatible systems running Windows/Linux.	Desktop/tower PC with x86‑64 CPU and discrete GPU.
PCH	Platform Controller Hub — the modern Intel chipset, handling I/O functions for peripherals.	The Z690 PCH provides USB, SATA, and additional PCIe lanes.
PSU	Power Supply Unit — converts AC mains to regulated DC rails to power computer components; rated by wattage and efficiency.	ATX PSUs providing +12V/+5V/+3.3V; 80 PLUS efficiency tiers; modular cabling.
RTC	Real-Time Clock — hardware clock that keeps time across reboots/power cycles, often backed by a battery.	System reads RTC (CMOS/ACPI) at boot to set the OS clock.
SBC	Single-Board Computer — complete computer on a single circuit board integrating CPU, memory, storage, and I/O.	Raspberry Pi, BeagleBone; runs Linux for embedded/edge.
SIMT	Single Instruction, Multiple Threads — GPU execution model where groups of threads execute the same instruction on different data.	NVIDIA warp execution; branch divergence reduces efficiency.
SMBIOS	System Management BIOS — firmware tables that describe hardware to the OS.	DMI/SMBIOS tables expose model, memory, and slots.
SoC	System on Chip — integrated circuit that consolidates CPU cores, GPU, memory controllers, and I/O peripherals on a single die/package.	Smartphone/tablet SoCs (Apple M‑series, Qualcomm Snapdragon); embedded ARM SoCs.
TPM	Trusted Platform Module — hardware-based security chip for keys and attestation.	TPM 2.0 used by Secure Boot and disk encryption.
VHDL	VHSIC Hardware Description Language — a hardware description language used in electronic design automation to describe digital and mixed-signal systems.	Design FPGAs and ASICs with VHDL; entity, architecture, process.
Historical
PDA	Personal Digital Assistant — a handheld device that combined computing, telephone/fax, and networking features; a precursor to the smartphone.	Palm Pilot, Apple Newton, Windows CE devices.
PIC	Programmable Interrupt Controller — legacy interrupt controller (e.g., Intel 8259A) that routes hardware IRQs to the CPU.	Classic x86 uses dual 8259 PICs remapped during OS init.
PIT	Programmable Interval Timer — legacy timer chip (e.g., Intel 8253/8254) that divides a ~1.193182 MHz input clock to produce periodic interrupts for task scheduling and timekeeping.	Configure PIT channel 0 to generate IRQ0 for early OS scheduler ticks; retained as a fallback timer during boot.

Firmware

Acronym	Meaning	Example
ACPI	Advanced Configuration and Power Interface — standard for power management and device configuration via tables provided by firmware.	ACPI tables (DSDT/SSDT) describe devices and power states to the OS.
AML	ACPI Machine Language — pseudo-code bytecode interpreted by the OS to evaluate ACPI objects and methods from the DSDT/SSDTs.	AML interpreter in the kernel executes methods to handle power events.
DSDT	Differentiated System Description Table — primary ACPI table from firmware containing the base definition of devices and power objects in AML.	The OS loads and interprets the DSDT at boot to enumerate devices.
FADT	Fixed ACPI Description Table — ACPI table that provides pointers to other tables and defines fixed hardware register blocks.	Contains addresses for power management timers and SCI interrupt info.
GRUB	GRand Unified Bootloader — a popular bootloader from the GNU project, used by most Linux distributions.	The GRUB menu for selecting an OS to boot; grub.cfg configuration.
MADT	Multiple APIC Description Table — ACPI table that describes all the interrupt controllers (APICs, IOAPICs) in the system.	The OS uses the MADT to initialize CPUs and route interrupts in an SMP system.
PnP	Plug and Play — automatic device detection, enumeration, and configuration by the OS/firmware, minimizing manual setup and IRQ/DMA conflicts.	ACPI/PCI PnP; USB devices enumerated and drivers auto‑loaded.
PSCI	Power State Coordination Interface — ARM standard for power management, allowing an OS to request power state changes from system firmware.	OS uses PSCI calls for CPU hotplug, idle, and system shutdown.
RSDP	Root System Description Pointer — firmware structure that locates the main ACPI tables (RSDT/XSDT) in memory for the OS.	The OS scans for the "RSD PTR " signature in low memory to find the RSDP.
RSDT	Root System Description Table — 32-bit ACPI table that contains pointers to all other description tables.	Superseded by the 64-bit XSDT on modern systems.
SBI	Supervisor Binary Interface — standard interface between a RISC‑V supervisor OS and machine‑mode firmware providing services (timers, IPIs, power, console) via SBI calls; commonly implemented by OpenSBI.	Boot flow: ROM/FSBL → OpenSBI (SBI firmware) → U‑Boot/Linux; OS issues ecall to SBI for privileged services.
SCI	System Control Interrupt — a dedicated interrupt used by ACPI to signal power management and other system events to the OS.	ACPI SCI handler for lid open/close or power button events.
SMI	System Management Interrupt — a high-priority interrupt that causes the CPU to enter System Management Mode (SMM).	Triggered by hardware or firmware to handle platform-specific events.
SMM	System Management Mode — a special-purpose CPU mode in x86 for handling system-wide functions like power management and proprietary OEM code, transparent to the OS.	SMI handler for power button events; legacy USB keyboard emulation.
SSDT	Secondary System Description Table — additional ACPI tables containing AML definitions that supplement or modify the DSDT.	Used for device-specific configuration or hot-plug support.
UEFI	Unified Extensible Firmware Interface — modern firmware replacing legacy BIOS with a flexible boot and runtime services model.	UEFI boot managers, GPT disks, Secure Boot.
XSDT	Extended System Description Table — 64-bit version of the RSDT that contains pointers to all other ACPI description tables.	Used by modern 64-bit operating systems to find ACPI tables.
Legacy
CSM	Compatibility Support Module — UEFI component that provides legacy BIOS services to boot non‑UEFI OSes and option ROMs; phased out on modern systems.	Enable CSM to boot legacy MBR media or old GPUs with legacy option ROMs.
Historical
APM	Advanced Power Management — legacy firmware interface for power management, superseded by ACPI.	APM BIOS calls for sleep/shutdown on pre-ACPI systems.
BIOS	Basic Input/Output System — legacy PC firmware that initializes hardware and boots the OS.	PC firmware POST and boot sequence on legacy/CSM systems.
POST	Power-On Self-Test — diagnostic sequence run by firmware (esp. legacy BIOS) at startup to check hardware integrity.	Beep codes on failure; memory/drive checks during boot.

Culture & Misc

Acronym	Meaning	Example
AFAICT	As Far As I Can Tell — based on current understanding.	“AFAICT, the bug only affects Safari.”
AFAIK	As Far As I Know — indicates incomplete knowledge.	“AFAIK, we don't support Windows 7 anymore.”
AFK	Away From Keyboard — temporarily unavailable.	“AFK 10 mins, brb.”
ASAP	As Soon As Possible — urgent request or prioritization; avoid ambiguity by specifying a concrete timeframe when possible.	“Please review ASAP” → “Please review by EOD.”
ATM	At The Moment — current status may change.	“ATM we're blocked on upstream changes.”
BDFL	Benevolent Dictator For Life — long-term project leader.	Python’s BDFL history.
BOFH	Bastard Operator From Hell — cynical sysadmin trope.	Humor in ops culture.
BRB	Be Right Back — brief step away.	“BRB, grabbing coffee.”
BTW	By The Way — add side note/context.	“BTW, the API changed in v2.”
DM	Direct Message — private one-to-one message in chat/social platforms.	“Send me a DM with the logs.”
ELI5	Explain Like I'm Five — request for simple explanation.	“ELI5 how RSA works.”
EOD	End Of Day — end of a working day; common deadline shorthand.	“I'll have a draft ready by EOD.”
EOW	End Of Week — end of the current work week; deadline shorthand.	“Targeting EOW for the feature toggle rollout.”
EOY	End Of Year — end of the calendar or fiscal year; deadline shorthand.	“Let's target EOY for GA after extended beta.”
ETA	Estimated Time of Arrival — expected completion/arrival time.	“ETA for fix is 3pm.”
FFS	For F***'s Sake — expression of frustration or exasperation; avoid in formal communication.	“FFS, the build broke again.”
FOMO	Fear Of Missing Out — anxiety about missing experiences or opportunities others are having.	“Skip the release party? FOMO is real.”
FTW	For The Win — enthusiastic endorsement or celebration of something that worked well.	“Feature flags FTW — painless rollback.”
FUD	Fear, Uncertainty, Doubt — disinformation tactic.	Competitor FUD.
FWIW	For What It's Worth — modest preface to share input without asserting authority.	“FWIW, retry with exponential backoff.”
FYI	For Your Information — share info without requiring action.	“FYI: maintenance window Sunday 2am.”
GTK	Good To Know — acknowledges helpful info.	“Rate limit resets hourly — GTK.”
HN	Hacker News — tech news and discussion site run by Y Combinator.	Post a launch on news.ycombinator.com; join the discussion.
HTH	Hope This Helps — friendly sign‑off when providing assistance or an answer.	“HTH! Ping me if you need more details.”
ICYMI	In Case You Missed It — pointer to noteworthy info shared earlier.	“ICYMI, the outage postmortem is posted.”
IDK	I Don't Know — lack of information.	“IDK the root cause yet; investigating.”
IIRC	If I Recall Correctly — hedged memory.	“IIRC, that was fixed in 1.2.”
IIUC	If I Understand Correctly — confirm interpretation.	“IIUC, only a config change is needed.”
IMHO	In My Humble Opinion — opinion preface.	“IMHO, we should simplify.”
IMO	In My Opinion — opinion preface; a slightly less self-deprecating variant of IMHO.	“IMO, we should ship feature‑flagged.”
IRL	In Real Life — referring to the physical/offline world as opposed to online/virtual contexts.	“Let's meet IRL next week.”
LGTM	Looks Good To Me — code review approval.	“LGTM, ship it.”
LMGTFY	Let Me Google That For You — snarky suggestion to search the web first; use sparingly as it can come across as dismissive.	“LMGTFY: how to clear npm cache.”
LMK	Let Me Know — request a follow-up.	“LMK if the deploy finishes.”
MAME	Multiple Arcade Machine Emulator — a free and open-source emulator designed to recreate the hardware of arcade game systems in software.	Preserve gaming history by playing classic arcade games with MAME.
MOTD	Message Of The Day — login banner/notice.	/etc/motd on login.
NBD	No Big Deal — indicates something is minor or not worth worrying about.	“Missed the standup — NBD.”
NIH	Not Invented Here — bias to build your own instead of using existing solutions.	Replacing a mature library with custom code.
NP	No Problem — acknowledgment that a request is fine or a task is acceptable.	“NP, I can take this.”
NSFW	Not Safe For Work — content that may be inappropriate for professional settings.	“NSFW: explicit language/images; open privately.”
OOO	Out Of Office — unavailable for work/response.	“OOO until Monday.”
OP	Original Poster — thread/issue creator.	“Per OP’s repro steps …”
OT	Off Topic — content not related to the main subject/thread.	“OT: anyone tried the new keyboard switches?”
OTOH	On The Other Hand — introduces a contrasting point or alternative perspective.	“We can optimize now; OTOH, premature optimization adds risk.”
PEBKAC	Problem Exists Between Keyboard And Chair — user error.	Misconfigured client settings.
PITA	Pain In The Ass — something annoying or cumbersome; avoid in formal communication.	“That migration was a PITA.”
PTO	Paid Time Off — time away from work.	“On PTO next week.”
QQ	Quick Question — brief, low‑effort question or nudge for a short answer.	“QQ: is staging using the new DB URL?”
RIP	Rest In Peace — tongue-in-cheek epitaph for a feature, service, or idea that just failed or was deprecated.	“RIP staging cluster after that migration.”
RPG	Role-Playing Game — a game in which players assume the roles of characters in a fictional setting.	Tabletop RPGs like D&D; computer RPGs like Final Fantasy.
RTFM	Read The F***ing Manual — read docs first.	git rebase --help.
SME	Subject-Matter Expert — domain expert.	Security SME review.
SMH	Shaking My Head — expresses disappointment or disbelief.	“Prod creds in a script? SMH.”
SO	Stack Overflow — popular Q&A site for programming and software development.	Link to an accepted SO answer for a solution/workaround.
TANSTAAFL	There Ain't No Such Thing As A Free Lunch — highlights that every choice has trade‑offs or hidden costs; nothing is truly free.	“TANSTAAFL: caching speeds reads but adds complexity/invalidation.”
TBA	To Be Announced — details later.	Rollout date TBA.
TBD	To Be Determined — not finalized.	Owner TBD after planning.
TBH	To Be Honest — candid preface.	“TBH, refactor first.”
TFA	The F***ing Article — read the article.	TFA explains REST vs RPC.
TIA	Thanks In Advance — polite sign‑off indicating appreciation for help to come; consider whether it pressures recipients.	“TIA for reviewing the PR.”
TIL	Today I Learned — sharing a new fact or insight just learned.	“TIL git worktree simplifies multi-branch checkouts.”
TL;DR	Too Long; Didn't Read — summary.	TL;DR: Use approach B.
TLA	Three-Letter Acronym — meta-acronym.	“Another TLA.”
TTYL	Talk To You Later — casual sign-off indicating you’ll continue the conversation later.	“Gotta run — TTYL.”
WCGW	What Could Go Wrong — tongue-in-cheek before risk.	“Deploy Friday, WCGW?”
WFH	Work From Home — remote from home.	“WFH today.”
WTF	What The F*** — expression of surprise, confusion, or frustration; avoid in formal communication.	“WTF happened to the build pipeline?”
YMMV	Your Mileage May Vary — results differ.	Different env outcomes.
YOLO	You Only Live Once — humorously justifies taking a risk; use with care.	"YOLO deploy" on Friday — probably don't.
Legacy
MUD	Multi-User Dungeon — a text-based, online multiplayer role-playing game; a precursor to MMORPGs.	Connect via Telnet; DikuMUD, LPMud, MUSH/MUCK/MOO variants.

Organizations

Acronym	Meaning	Example
ACM	Association for Computing Machinery — international learned society for computing, publishing journals, conferences, curricula, and best practices.	ACM SIGs (SIGGRAPH, SIGPLAN), ACM Digital Library, Turing Award.
ANSI	American National Standards Institute — U.S. standards organization that oversees and coordinates standards development and accredits standards bodies.	ANSI C (C89/C90) standardization; coordinates U.S. positions in ISO/IEC JTC 1.
ASF	Apache Software Foundation — non‑profit that supports Apache open source projects and communities.	Apache HTTP Server, Hadoop, Kafka, Spark under the ASF.
BBN	Bolt Beranek and Newman — pioneering research and engineering firm (now BBN Technologies) that built the ARPANET IMPs, advanced routing research, and contributed foundational internet and defense networking work.	BBN designed ARPANET IMPs, hosted early TCP/IP research, and continued DARPA-funded networking projects.
CNCF	Cloud Native Computing Foundation — part of the Linux Foundation hosting cloud‑native projects and standards.	Kubernetes, Prometheus, Envoy; CNCF landscape and graduation levels.
ECMA	Ecma International — industry association for information and communication systems standards.	ECMAScript (JavaScript), C# (ECMA-334), CLI (ECMA-335).
EFF	Electronic Frontier Foundation — a non-profit organization defending civil liberties in the digital world.	Advocates for privacy, free speech, and innovation online.
FSF	Free Software Foundation — GNU/GPL steward.	Publishes GPL family.
GNU	GNU’s Not Unix — FSF project and philosophy.	GNU toolchain/userland.
IANA	Internet Assigned Numbers Authority — coordinates global IP addressing, DNS root zone management (with ICANN), and protocol parameter registries (ports, DHCP options, etc.).	Port numbers and protocol parameters registries; root zone management with ICANN.
NIC	Network Information Center — organization responsible for domain registration, IP allocation, and directory services in early networks; historically includes SRI-NIC (ARPANET) and national NICs.	SRI's NIC handled ARPANET hostnames and RFC distribution; modern NICs manage ccTLDs (e.g., RIPE NCC, AFRINIC roles).
ICANN	Internet Corporation for Assigned Names and Numbers — oversees the global DNS root, IP address allocation policy coordination, and domain name registries/registrars.	gTLD/ccTLD policies; WHOIS/RDAP; root zone stewardship.
IEEE	Institute of Electrical and Electronics Engineers — professional association and standards body producing technical standards.	IEEE 802 (Ethernet/Wi‑Fi), IEEE 754 floating‑point.
IETF	Internet Engineering Task Force — open standards body that develops and publishes internet standards as RFCs.	HTTP/1.1 (RFC 723x), TLS (RFC 8446), QUIC (RFC 9000); working groups and I-Ds.
ISO	International Organization for Standardization — independent, non‑governmental international standards body.	ISO 8601 dates/times; ISO/IEC 9899 (C), ISO/IEC 14882 (C++).
ITU‑T	International Telecommunication Union — Telecommunication Standardization Sector; develops telecom standards (Recommendations) for networks, media, and services.	ITU‑T H.264/H.265 (with ISO/IEC), G.711/G.722 codecs; numbering, signaling, and transport Recs.
NIST	National Institute of Standards and Technology — U.S. federal agency that develops standards, guidelines, and measurements to improve technology, cybersecurity, and commerce.	NIST SP 800‑53/63/171 security guidelines; NIST hash/SHA competition; time services.
OASIS	OASIS Open — consortium that develops open standards for security, identity, content, and more.	SAML, STIX/TAXII, KMIP; technical committees and OASIS specifications.
OMG	Object Management Group — consortium that develops technology standards, notably modeling/specification standards.	UML, CORBA, BPMN standards; working groups and specifications.
OSI	Open Source Initiative — OSI-approved licenses.	Open Source Definition stewardship.
OWASP	Open Web Application Security Project — a non-profit foundation focused on improving software security.	The OWASP Top 10 list of critical web application security risks; OWASP ZAP scanner.
PARC	Palo Alto Research Center (formerly Xerox PARC) — famed industrial research lab that pioneered modern computing breakthroughs in GUIs, Ethernet, laser printing, and object-oriented systems.	PARC's Alto workstation, Smalltalk environment, and Ethernet prototypes seeded foundational ideas adopted across the industry.
PCI-SIG	Peripheral Component Interconnect Special Interest Group — consortium that develops and maintains PCI and PCI Express specifications and compliance programs.	PCIe 5.0/6.0 specs, CEM/ECNs; compliance workshops and device interoperability testing.
SPEC	Standard Performance Evaluation Corporation — develops industry‑standard benchmarks for computing performance and energy.	SPEC CPU, SPECjbb, SPECpower; widely cited performance metrics.
TPC	Transaction Processing Performance Council — benchmarks for database and transaction processing systems.	TPC‑C (OLTP), TPC‑H/TPC‑DS (analytics), audited results and full disclosure reports.
W3C	World Wide Web Consortium — standards body that develops web specifications and recommendations.	HTML/CSS/DOM specs; Working Groups and drafts at w3.org.
WHATWG	Web Hypertext Application Technology Working Group — community maintaining living standards for HTML, DOM, and related web platform technologies.	HTML Living Standard; DOM and URL standards co‑developed with browsers.

Licensing & Open Source

Acronym	Meaning	Example
AGPL	GNU Affero GPL — copyleft with network-use clause.	SaaS must release source of modifications.
BSD	Berkeley Software Distribution — permissive license family.	BSD-2, BSD-3 clause variants.
EULA	End-User License Agreement — contract between software provider and end user defining usage rights/restrictions; common for proprietary software.	Accept EULA during installation; governs redistribution and usage.
FLOSS	Free/Libre and Open Source Software — umbrella term.	General discussions of FLOSS.
FOSS	Free and Open Source Software — umbrella term.	FOSS projects and communities.
GPL	GNU General Public License — strong copyleft.	Derivatives must remain open.
LGPL	GNU Lesser GPL — weak copyleft for linking.	Use in libraries linkable from proprietary apps.
MIT	MIT License — simple permissive license.	Many JS libs under MIT.
OSS	Open Source Software — software under OSI licenses.	OSS adoption.