DOS/4G is a

32-bit In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in a maximum of 32- bit units. Compared to smaller bit widths, 32-bit computers can perform la ...

DOS extender A DOS extender is a computer software program running under DOS that enables software to run in a protected mode environment even though the host operating system is only capable of operating in real mode. DOS extenders were initially developed ...

developed by Rational Systems (later

Tenberry Software Tenberry Software (previously Rational Systems) was a software company notable for the development of DOS/16M and DOS/4G, which were the first industry standard DOS extenders. See also * Phar Lap Phar Lap (4 October 1926 – 5 April 193 ...

). It allows

DOS DOS (, ) is a family of disk-based operating systems for IBM PC compatible computers. The DOS family primarily consists of IBM PC DOS and a rebranded version, Microsoft's MS-DOS, both of which were introduced in 1981. Later compatible syste ...

programs to eliminate the 640 KB

conventional memory In DOS memory management, conventional memory, also called base memory, is the first 640 kilobytes of the memory on IBM PC or compatible systems. It is the read-write memory directly addressable by the processor for use by the operating system ...

limit by addressing up to 64 MB of

extended memory In DOS memory management, extended memory refers to memory above the first megabyte (220 bytes) of address space in an IBM PC or compatible with an 80286 or later processor. The term is mainly used under the DOS and Windows operating systems. D ...

Intel 80386 The Intel 386, originally released as the 80386 and later renamed i386, is the third-generation x86 architecture microprocessor from Intel. It was the first 32-bit computing, 32-bit processor in the line, making it a significant evolution in ...

and above machines.

Features

Functioning as a highly flexible and reusable memory extension library, DOS/4G allowed programmers to access extended memory without writing specialized code. It embeds itself in the executable file at linking time and executes before main application code, so usually DOS/4G initialization messages show up at launch. It can in principle operate within

MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few op ...

PC DOS PC or pc may refer to: Arts and entertainment * Player character or playable character, a fictional character controlled by a human player, usually in role-playing games or computer games * '' Port Charles'', an American daytime TV soap opera * ...

DR-DOS DR-DOS is a disk operating system for IBM PC compatibles, originally developed by Gary A. Kildall's Digital Research, Inc. and derived from Concurrent PC DOS 6.0, which was an advanced successor of CP/M-86. Upon its introduction in 198 ...

and other DOS clones, the DOS boxes of

OS/2 OS/2 is a Proprietary software, proprietary computer operating system for x86 and PowerPC based personal computers. It was created and initially developed jointly by IBM and Microsoft, under the leadership of IBM software designer Ed Iacobucci, ...

Microsoft Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...

Windows NT Windows NT is a Proprietary software, proprietary Graphical user interface, graphical operating system produced by Microsoft as part of its Windows product line, the first version of which, Windows NT 3.1, was released on July 27, 1993. Original ...

and

Windows 95 Windows 95 is a consumer-oriented operating system developed by Microsoft and the first of its Windows 9x family of operating systems, released to manufacturing on July 14, 1995, and generally to retail on August 24, 1995. Windows 95 merged ...

, and DOS emulators such as

DOSBox DOSBox is a free and open-source MS-DOS emulator. It supports running programs primarily video games that are otherwise inaccessible since hardware for running a compatible disk operating system (DOS) is obsolete and generally unavailab ...

. However, in practice few DOS/4G games or other applications will run on non-DOS-based versions of

Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...

, including

Windows 2000 Windows 2000 is a major release of the Windows NT operating system developed by Microsoft, targeting the server and business markets. It is the direct successor to Windows NT 4.0, and was Software release life cycle#Release to manufacturing (RT ...

and

Windows XP Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct successor to Windows 2000 for high-end and business users a ...

, since none of these allow direct access to the hardware as was used for display rendering in those days.

History

Rational Systems first announced DOS/4G in July 1991. It was available immediately, at a price of US$5000 and up. DOS/4GW 1.95 was a free limited edition of DOS/4G and was included with the Watcom C compiler with a commercial re-distribution license. It was made widely popular by computer games like ''

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Tomb Raider ''Tomb Raider'', known as ''Lara Croft: Tomb Raider'' from 2001 to 2008, is a media franchise that originated with an Action-adventure game, action-adventure video game series created by British video game developer Core Design. The franchise i ...

''. Initial versions of DOS/4G had trouble with secondary DMA channels on the

ISA bus Isa or ISA may refer to: Places * Isa, Amur Oblast, Russia * Isa, Kagoshima, Japan * Isa, Nigeria * Isa District, Kagoshima, former district in Japan * Isa Town, middle class town located in Bahrain * Mount Isa, Queensland, Australia * Mou ...

, which prevented 16-bit devices like Gravis Ultrasound series from normally functioning; Gravis even had to develop PREPGAME, a patch utility which updated the game executable with a new version 1.97 to fix the incompatibility. In case of problems, DOS/4G or DOS/4GW can be replaced with the newer and free

DOS/32 DOS/32 is an advanced 32-bit DOS extender created for replacing DOS/4GW extender and compatibles. This extender can be used in various environments, from embedded systems to DOS emulators, by both developers and end users alike. Unlike DOS/4GW, D ...

; a patch utility can even replace DOS/4G code embedded inside a compiled executable file.TOOLS:DOS32A - DOSBoxWiki
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References

External links

DOS/4GW FAQ
DOS extenders {{DOS-stub