GA: Global Arrays
The Global Arrays (GA) is a public domain toolkit that provides an efficient and portable shared-memory programming interface for distributed-memory computers. Unlike other shared-memory environments, the GA model exposes to the programmer the non-uniform memory access (NUMA) characteristics of the high performance computers and acknowledges that access to a remote portion of the shared data is slower than to the local portion. The locality information for the shared data is available, and a direct access to the local portions of shared data is provided. Global Arrays have been designed to complement rather than substitute for the message-passing programming model. The programmer is free to use both the shared-memory and message-passing paradigms in the same program, and to take advantage of existing message-passing software libraries. Global Arrays are compatible with the Message Passing Interface (MPI).

GAMS: General Algebraic Modeling System
The General Algebraic Modeling System (GAMS) is a high-level modeling system for mathematical programming problems. The program itself consists of a language compiler and a group of integrated solvers. Thus, GAMS is not a solver itself.

Gas: GNU Assembler
GNU assembler (Gas) is the default GNU Compiler Collection (GCC) back-end and is used to compile Linux and other operating systems such as the GNU operating system. It is a part of the GNU Binutils package. It runs and assembles on and for a number of different architectures. Gas uses the AT&T assembler syntax, instead of the Intel syntax used in many other assemblers.

GCA
In computing, GCA is a freeware compression utility created in 2000 by Shin-ichi Tsuruta. GCA is a compressed archive format. It has higher compression capabilities than ZIP, especially with binary files. The next generation of GCA is 'DGCA'.

GCC: GNU Compiler Collection
The GNU Compiler Collection (GCC) is a set of programming language compilers produced by the GNU Project. It is free software distributed by the Free Software Foundation (FSF) under the GNU GPL and GNU LGPL, and is a key component of the GNU toolchain. It is the standard compiler for the free software Unix-like operating systems, and several proprietary operating systems, notably Apple Mac OS X. Originally named the GNU C Compiler, because it only handled the C programming language, GCC was later extended to compile C++, Objective-C, Java, Fortran, and Ada among others.

GCJ: GNU Compiler for Java
The GNU Compiler for Java (GCJ) is a compiler for the Java programming language that is part of the GNU Compiler Collection (GCC). It can compile Java source code to either Java Virtual Machine bytecode, or directly to machine code for any of a number of CPU architectures. It can also compile class files containing bytecode or entire Java archives (JARs) containing such class files into machine code. Almost all of the runtime library used by GCJ come from the GNU Classpath project.

GDB: GNU Debugger
GNU Debugger (GDB) is the standard debugger for the GNU software system. It is a portable debugger that runs on many Unix-like systems and works for many programming languages, including C, C++, and FORTRAN. Originally written by Richard Stallman in 1988, GDB is free software released under the GNU General Public License. GDB offers extensive facilities for tracing and altering the execution of computer programs.

GDL: GNU Data Language
GNU Data Language(GDL) is a free IDL (Interactive Data Language) compatible incremental compiler. It runs existing IDL programs from the Research Systems Inc.

GDM:  GNOME Display Manager
GNOME Display Manager(GDM) provides an alternate display manager for the X Window System. The X Window System by default uses the X display manager (XDM). However, resolving XDM configuration issues typically involves using the command line. GDM allows users to customize or troubleshoot settings without having to resort to a command line. Users can pick their session type on a per-login basis. GDM also features easy customisation with themes.

Geeklog
Geeklog is Open-Source software that works as a Weblog, CMS or Web Portal. Geeklog is written in PHP and uses MySQL as a backend database. Geeklog allows you to create your own virtual community portal complete with user administration, story posting, customised look, comments, polls, calendar, web links, content syndication, and more.

Generic Software
Generic Software, contrast with "custom software", refers to the ready-made software, traditionally shrink-wrapped but downloadable in today's market. 

GeoGebra
GeoGebra is a free dynamic mathematics software that joins [[geometry[[, [[algebra[[ and [[calculus[[. It is developed for education in secondary schools by Markus Hohenwarter at the University of Salzburg.

Geronimo Application Server
The Geronimo Application Server is an open source application server developed by the Apache Software Foundation, and it is under the Apache licence. The Geronimo application server has already met the Sun J2EE 1.4 Technology Compatibility Kit (TCK) since version 1.0 M4.

gFTP
gFTP is a free/open source multithreaded FTP client. It is most used on Unix-like systems, but it can be used on Microsoft Windows and Mac OS X. It includes both a GUI (which utilizes the GTK+) and a command-line interface. gFTP is released under the terms of the GPL and has been translated into 41 languages.

GHC: Glasgow Haskell Compiler
Glasgow Haskell Compiler (GHC), also known as Glorious Haskell Compiler, is an open source native code compiler for the functional programming language Haskell which was developed at the University of Glasgow.

Ghost: General Hardware-Oriented Software Transfer
General Hardware-Oriented Software Transfer (Ghost) is a disk cloning program, originally produced by Binary Research, but purchased by Symantec in 1998. The Ghost program launched the market for disk-cloning software.

GIFT: GNU Image Finding Tool
GNU Image Finding Tool (GIFT) is a Content Based Image Retrieval System (CBIRS). The GIFT is based on Viper, the result of a research effort at the Vision Group at the computer science center of the University of Geneva. The GIFT is an open framework for content-based image retrieval. It is designed to accommodate new ways of querying the framework. The protocol for client-server communication, MRML, is XML based and fully documented. This aims to promote code reuse among researchers and application developers.

GIMP: GNU Image Manipulation Program
GNU Image Manipulation Program (GIMP) is a bitmap graphics editor, a program for creating and processing raster graphics. It also has some support for vector graphics. The project was started in 1995 by Spencer Kimball and Peter Mattis and is now maintained by a group of volunteers; it is licensed under the GNU General Public License.

glibc: GNU C Library
The GNU C Library (glibc) is GNU's C standard library, a free software package available under the GNU Lesser General Public License. Glibc is used in systems which run many different kernels and different hardware architectures. Its most common use is in Linux systems on x86 hardware, but officially supported hardware includes: x86, Motorola 680x0, DEC Alpha, PowerPC, ARM, ETRAX CRIS, MIPS, s390, and SPARC. 

GLPK: GNU Linear Programming Kit
The GNU Linear Programming Kit (GLPK) is a software package intended for solving large-scale linear programming (LP), mixed integer programming (MIP), and other related problems. It is a set of routines written in ANSI C and organized in the form of a callable library. The package is part of the GNU Project, which is released under the GNU General Public License.

Glueware
Glueware is a type of software that can be used to "glue" or integrate systems, software components and databases together, to form a seamless integrated system.

Gmail Drive
Gmail Drive, a free shell namespace extension ("add-on") for Microsoft Windows Explorer, makes it possible to create a new network share on the workstation. In order to use this add-on, you need a Gmail account from Google Gmail. The add-on enables you to use the normal Windows desktop file copy and paste commands to transfer files to and from your Gmail account just as if it was physically located on your local network.

GML: Generalized Markup Language
Generalized Markup Language (GML) is a set of macros (tags) for the IBM text formatter, "SCRIPT". SCRIPT is the main component of IBM's Document Composition Facility (DCF). GML simplifies the description of a document in terms of its format, organization structure and content parts and their relationship, and other properties. GML markup (or tags) describe such parts as chapters, important sections, and less important sections (by specifying heading levels), paragraphs, lists, tables, and so forth. Using GML, a document is marked up with tags that define what the text is, in terms of paragraphs, headers, lists, tables, and so forth. The document can then be automatically formatted for various devices simply by specifying a profile for the device. For example, it is possible to format a document for a laser printer or a line (dot matrix) printer or for a screen simply by specifying a profile for the device without changing the document itself.

GNAT: GNU NYU Ada Translator
GNU NYU Ada Translator (GNAT) is the GNU Ada Compiler based on GNU Compiler Collection (GCC). The front-end and runtime are written in Ada, and are licensed using the General Public License.

GNAVI
GNAVI is an open source visual software development environment licensed under the GPL. The language foundation of GNAVI is the international standard of engineering, Ada. GNAVI for Microsoft Windows offers comparable features to Delphi and Visual Basic including use of Active X controls and the ability to interface with .NET and Java.

GNOME:  GNU Network Object Model Environment
GNU Network Object Model Environment (GNOME) project is an international effort to create an easy-to-use computer desktop environment built entirely from software considered free by the Free Software Foundation.

GNU Arch
GNU arch is a software revision control system that is part of the GNU Project and licensed under the GNU General Public License. It is used to keep track of the changes made to a source tree and to help programmers combine and otherwise manipulate changes made by multiple people or at different times. GNU arch is decentralized, removing the need for a central server for which developers have to be authorized in order to contribute.

GNU Aspell
GNU Aspell (Aspell) is the standard spelling checker software for the GNU software system designed to replace Ispell. It also compiles for other Unix-like operating systems and Microsoft Windows. The main program is licensed under the GNU Lesser General Public License, the documentation under GNU Free Documentation Licence. Dictionaries for it are available for about 70 languages.

GNU Build System
The GNU build system, a part of GNU toolchain, is a suite of tools produced by the GNU project that assist in making packages portable to many UNIX-like systems.

GNU General Public License
GNU General Public License (GNU GPL) also known as General Public License (GPL) is a widely used free software license, originally written by Richard Stallman for the GNU project. The GNU Project was launched in 1984 to develop a complete UNIX style operating system which is free software: the GNU system. The latest version of the license, version 2, was released in 1991. The GNU Lesser General Public License (LGPL) is a modified version of the GPL, intended for some software libraries.

GNU Hurd
The GNU Hurd is a component of the core of the GNU operating system distributed as free software under the GPL. It is a set of servers (or daemons, in Unix-speak) that work on top of GNU Mach or the L4 microkernel. The Hurd aims to surpass Unix kernels in functionality, security, and stability, while remaining largely compatible with them. This is done by having the Hurd track the POSIX specification, while avoiding arbitrary restrictions on the user.

GNU Mach
GNU Mach, an implementation of the Mach microkernel, is the default microkernel in the GNU Hurd kernel of the GNU operating system. GNU Mach runs on IA-32 machines, and is expected to be ported to other computers. Mach is particularly well suited for SMP and network cluster techniques. Thread support is provided at the kernel level, and the kernel itself takes advantage of that. Network transparency at the IPC level makes resources of the system available across machine boundaries. GNU Mach is maintained by developers on the GNU project and distributed under GNU General Public License (GPL).

GNU MDK: GNU MIX Development Kit
The GNU MIX Development Kit(GNU MDK) is a software package for developing, running and debugging programs written in MIXAL, an assembly-like language for programming a fictional computer called MIX. It is a free package distributed under GNU General Public License (GPL).

GNU Readline
GNU readline is a software library created and maintained by the GNU project. It provides line-editing capabilities. For instance, in a readline-enabled application, pressing C-b (CTRL-B) moves the cursor back one space, whereas C-f moves the cursor forward one space; C-r searches in history; these key bindings (which are the default, although bindings like vi's are optional) are taken from one of GNU's earliest and most popular projects, the text editor Emacs. Readline supports a variety of advanced features, including a kill ring (a more flexible version of a copy/paste clipboard) and tab completion. As a cross-platform library, readline allows many applications on various systems to exhibit identical line-editing behavior. It is a free package distributed under GNU General Public License (GPL).

GNU Robots
GNU Robots is a computer game for programmers. The goal is to guide a robot simulation around a maze, consuming food, avoiding baddies, and collecting as many prizes as possible in the process. However, the player cannot control the robot once the game begins; the robot acts according to a Scheme script previously written by the player. It is a free package distributed under GNU General Public License (GPL).

GNU Savannah
GNU Savannah is a project of the Free Software Foundation, which serves as a collaborative software development management system for Free Software projects. Savannah currently offers CVS, mailing list, web hosting, file hosting, and bug tracking services. It is a free package distributed under GNU General Public License (GPL).

GNU Screen
GNU Screen is a GNU fullscreen console multiplexer which permits a user to multiplex one terminal into multiple terminals. Thus screen allows the user to perform several additional tasks over a normal terminal. It is a free package distributed under GNU General Public License (GPL).

GNU TEXMACS
GNU TEXMACS, alternatively called TeXmacs, is a free scientific word processor component of the GNU project, which was inspired by both TeX and GNU Emacs. The program allows you to write structured documents via a user-friendly WYSIWYG interface. New styles may be created by the user. The program implements high-quality typesetting algorithms and TeX fonts, which help the user to produce professional looking documents.

GNU Toolchain
The GNU toolchain refers to a collection of the programming tools produced by the GNU project. These tools form an integrated system that is used for programming both applications and operating systems. Parts of the toolchain are also widely used in the Solaris Operating Environment (which, in the opinion of many, needs the GNU tools for reasonable usability) and Microsoft Windows programming with Cygwin and MinGW/MSYS. Projects that are included in the GNU toolchain:
GNU make - build and compilation automation
The GNU Compiler Collection (GCC) - compilers for several languages
The GNU Binutils - linker, assembler and other tools
The GNU Debugger (GDB) - an interactive debugger
The GNU build system (autotools) - Autoconf, Autoheader, Automake, Libtool - makefiles generators 

GNU/kFreeBSD
GNU/kFreeBSD is an operating system that uses the kernel of FreeBSD in conjunction with GNU userland software. Currently, the following distributions of GNU/kFreeBSD are available: Debian GNU/kFreeBSD, Gentoo/FreeBSD. It should be noted that the k in kFreeBSD refers to the fact that only the kernel of the FreeBSD operating system is used.

GNU/Linux
GNU/Linux, simply called Linux in most cases, refers to all the variants GNU operating systems using the Linux kernel.

GNU/NetBSD
GNU/NetBSD is a term for an operating system using the NetBSD kernel but GNU userland software, like Debian GNU/NetBSD, a Debian version currently available for IA-32 and Alpha architectures.

GNU: Gnu's Not UNIX
GNU, a recursive acronym for “GNU's Not UNIX, is a project sponsored by the Free Software Foundation that develops and maintains a complete free UNIX like software environment including operating system kernel and utilities, editor, compiler and debugger. Variants of the GNU operating system, which use the kernel Linux, are now widely used; though these systems are often referred to as Linux, they are more accurately called GNU/Linux systems.

GNUstep
GNUstep is a free software implementation of NeXT's OpenStep Objective-C libraries (called frameworks), widget toolkit, and application development tools not only for Unix-like operating systems, but also for Microsoft Windows. It is part of the GNU project.

Goto
Goto, also spelled as "go to", "GO TO", "GOTO", is a construct and keyword found in several higher-level programming languages (e.g. Fortran, COBOL, BASIC, C) to cause an unconditional jump or transfer of control from one point in a program to another. The destination of the jump is usually indicated by a parameter after the command.

GPL: General Public License
General Public License(GPL) is a free license type applied to most software from the Free Software Foundation(FSF) and the GNU project and other authors who choose to use it. The normal licences as defined by the copyright law are designed to prevent users from sharing or changing it. By contrast, the General Public License is intended to provide the freedom to share and change software - to make sure the software including source code is open and free for all its users, distributors and modifiers (as long as the changes are clearly marked, the derivative work is not sold and is also licensed under the GPL.)

GPL: General Purpose Language
General Purpose Language(GPL), also known as general purpose programming language, is a programming language that can be used for any purposes. Examples of DSLs include C, C++, BASIC, FORTRAN, etc.

GPS: GNAT Programming Studio
GNAT Programming Studio (GPS), formerly known as the GNAT Programming System, is a free multi-language IDE for GNU/Linux, MS Windows and Solaris/Sparc. GPS uses GTK+ as graphical user interface. This IDE is released by AdaCore under the GNAT Modified General Public License.

Greenware
Greenware is a software license which provides an end user with the right to use a particular program or obtain the source code, if he makes an effort to help out the environment such as using only recycled computer paper, recycling the computer paper after using it, using public transport, etc.

Greyware
Greyware refers to a malicious software or code that is considered to fall in the "grey area" between normal software and a virus. Greyware is a term for which all other malicious or annoying software such as adware, spyware, trackware, and other malicious code and malicious shareware fall under.

Groupware
Groupware, also known as Collaborative software, is a type of computer software or computer-based systems that support groups of people engaged in a common task (or goal) and that provide an interface to a shared environment. It is the basis for computer supported cooperative work. Such software systems as mail, calendaring, chat, wiki belong into this category.

GSL: GNU Scientific Library
GNU Scientific Library (GSL) is a software library written in the C programming language for numerical calculations in applied mathematics and science. The GSL is part of the GNU project and is distributed under the GNU GPL.

GTK+: GIMP Toolkit
GIMP Toolkit (GTK+), licensed under the LGPL as a free (and open source) software, is one of the two most popular widget toolkits for the X Window System, intended for creating graphical user interfaces. GTK+ and Qt have supplanted Motif, previously the most widely-used X widget toolkit. GTK+ uses the C programming language, although its designers use an object-oriented paradigm. The GNOME platform bindings provide for C++ (gtkmm), Perl, Ruby, Java and Python (PyGTK) bindings; others have written bindings for many other programming languages (including Ada, D, Haskell, Pascal, PHP, and all .NET programming languages).

GTK-Qt
The GTK-Qt Theme Engine is a project allowing GTK to use Qt widget styles. It behaves like a normal GTK theme engine, but calls functions from Qt instead of doing the drawing itself.

GUI: Graphical User Interface
A graphical user interface (GUI) is a method of human interacting with a computer through direct manipulation of graphical images and widgets in addition to text. A program with a GUI runs under some windowing system (e.g. The X Window System, Apple Macintosh, Microsoft Windows, Acorn RISC OS, NEXTSTEP). The program displays certain icons, buttons, dialogue boxes etc. in its windows on the screen and the user controls it mainly by moving a pointer on the screen (typically controlled by a mouse) and selecting certain objects by pressing buttons on the mouse while the pointer is pointing at them.

Guiltware
Guiltware refers to the kind of shareware software that attempts to make the user register and pay for the software by exploiting the user's sense of guilt. For example, when people are using a un-registered version software, on-screen messages are displayed, usually when the program is started, reminding users that they have an unregistered version of the program that they should pay for if they intend to continue using it. Some programs will also display the message at random intervals while the program is in use.

GVN: Global value numbering
Global value numbering (GVN) is a compiler optimization based on the SSA intermediate representation. It sometimes helps eliminate redundant code that common subexpression evaluation (CSE) does not. At the same time, however, CSE may eliminate code that GVN does not, so both are often found in modern compilers. Global value numbering is distinct from local value numbering in that the value-number mappings hold across basic block boundaries as well, and different algorithms are used to compute the mappings.

GW Basic
GW-BASIC was a dialect of BASIC developed by Microsoft from BASICA, originally for Compaq. It is compatible with Microsoft/IBM BASICA, but was disk based and did not require the resources of the ROM included on IBM's machines. It was bundled with MS-DOS operating systems on IBM PC compatibles by Microsoft. Like other early microcomputer versions of BASIC, GW-BASIC lacked many of the structures needed for structured programming such as local variables, and GW-BASIC programs executed relatively slowly, due to the fact that it was an interpreted programming language. It did have a large number of graphics commands.

Gzip: GNU zip
GNU zip (gzip) is a GNU free software file compression program. It was created by Jean-loup Gailly and Mark Adler. gzip is based on the DEFLATE algorithm, which is a combination of LZ77 and Huffman coding. DEFLATE was intended as a replacement for LZW and other patent-encumbered data compression algorithms which, at the time, limited the usability of compress and other popular archivers. "gzip" is often also used to refer to the gzip file format.