 Tenberry Software's DOS/4GW startup banner Developed in the 1980s to cope with the memory limitations of MS-DOS and its derivatives, DOS extenders are programs which enable software to run under the protected mode environment initially introduced with the Intel 80286 processor and later expanded upon with the Intel 80386, even though host operating system is only capable of operating in real mode Image File history File links DOS4GWbanner. ...
Image File history File links DOS4GWbanner. ...
The 1980s refers to the years from 1980 to 1989. ...
Microsofts disk operating system, MS-DOS, was Microsofts implementation of DOS, which was the first popular operating system for the IBM PC, and until recently, was widely used on the PC compatible platform. ...
Protected mode is an operational mode of x86-compatible CPUs of the 80286 series or later. ...
AMD 80286 at 12 MHz. ...
The Intel386[1] is a microprocessor which was used as the central processing unit (CPU) of many personal computers from 1986 until 2007. ...
Real mode (also called real address mode in Intels manuals) is an operating mode of 80286 and later x86-compatible CPUs. ...
DOS extender operation
Strictly speaking, a DOS extender is a program that does exactly what its name implies: it "extends" DOS so that programs running in protected mode can transparently interface with the underlying API provided MS-DOS (and compatible) operating system. This was necessary because many of the functions provided by DOS required 16-bit segment and offset addresses pointing to memory locations within the first megabyte of memory. Protected mode, however, uses an incompatible addressing method where the segment registers (now called selectors) are used to point to an entry in a table which describes the characteristics of the segment. The two methods of addressing are mutually exclusive, with the processor having to make costly switches to real (or V86) mode to services non-protected mode requests. API may refer to: In computing, application programming interface In petroleum industry, American Petroleum Institute In education, Academic Performance Index This page concerning a three-letter acronym or abbreviation is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ...
Conventional memory is the first 640 kibibytes of an IBM PCs memory. ...
Relationship between pages addressed by virtual addresses and the frames in physical memory, within a simple address space scheme. ...
In the 80386 and later, Virtual 8086 mode, also called virtual real mode (or VM86), allows the execution of real mode applications that violate the rules under the control of a protected mode operating system. ...
In addition to setting up the environment and loading the actual program to be executed, the DOS extender also provides (amongst other things) a translation layer that maintains buffers allocated below the 1MB real mode memory barrier. These buffers are used to transfer data between the underlying real mode operating system and the protected mode program. Since switching between real/V86 mode and protected mode is a relatively time consuming operation, the extender attempts to minimize the number of switches by duplicating the functionality of many real mode operations within its own protected mode environment. As DOS uses interrupts extensively for communication between the operating system and user level software, DOS extenders intercepted many of the common hardware (e.g. the real-time clock and keyboard controller) and software (e.g. DOS itself and the mouse API). Some extenders also handle other common interrupt functions, such the video BIOS routines. In computing, a buffer is a region of memory used to temporarily hold output or input data, comparable to buffers in telecommunication. ...
In computer engineering, an interrupt is a signal from a device which typically results in a context switch: that is, the processor sets aside what its doing and does something else. ...
A real-time clock (RTC) is a computer clock (most often in the form of an integrated circuit chip) that keeps track of the current time even when the computer is turned off. ...
Essentially, a DOS extender is like a miniature operating system, handling much of the functionality of the underlying operating system itself.
Limitations The first DOS extenders took advantage of the 16-bit protected mode features introduced with the 80286 processor. In 16-bit protected mode software could access up to 16 megabytes of memory, which at the time was a huge increase over the 640K limit software had been restricted to since the PC's introduction.
The 80386 processor improved upon the 286 in several ways, one of which was to increase the size of the fields in the segment descriptor from the 286's 16-bit base address and limit, to a full 32-bit base address with a 20-bit limit. The 386 also introduced a flag in the descriptor entry to indicate the granularity of the segment limit, which could be either as bytes or 4KB pages. This had the effect of increasing the maximum memory limit to 4 gigabytes.
Not all DOS extenders are capable of accessing the full amount of memory installed in the computer, however. In order to maintain compatibility with older software, extenders must work with any pre-existing memory management software already running (such as extended memory managers like HIMEM and expanded memory managers like EMM386). When a memory manager is running, the DOS extender must cooperate with it to ensure that the extender does not attempt to use any resources already allocated by the memory manager. Any limitations of the memory management software are thus inherited by the DOS extender. For example, MS-DOS 6.22's HIMEM could only handle 64MB of memory, while EMM386 could only grant access to 32MB of expanded memory. Extended memory refers to memory above the first megabyte of address space in an IBM PC with an 80286 or later processor. ...
HIMEM is a DOS device driver which allows DOS programs to store data in extended memory via the Extended Memory Specification (XMS). ...
Expanded Memory was a trick invented around 1984 that provided more memory to byte-hungry, business-oriented MS-DOS programs. ...
The name EMM386 was used for the expanded memory managers of both Microsofts MS-DOS and Digital Researchs DR-DOS, which created expanded memory using extended memory on Intel 80386 CPUs. ...
Some extenders also took advantage another feature in protected mode: virtual memory. Using the VMM features of the processor, the extender can theoretically provide an application with access to the entire 4GB address space by paging blocks of memory from a secondary storage device (such as a hard disk drive) in and out of physical memory. Not all extenders supported this feature, however, as it adds additional complexity to the extender (and gives the user a reason to upgrade to a "professional" version of the DOS extender). The program thinks it has a large range of contiguous addresses; but in reality the parts it is currently using are scattered around RAM, and the inactive parts are saved in a disk file. ...
A hard disk drive (HDD), commonly referred to as a hard drive, hard disk or fixed disk drive,[1] is a non-volatile storage device which stores digitally encoded data on rapidly rotating platters with magnetic surfaces. ...
Development history
Tenberry Software's DOS/4G product logo The DOS extender was arguably invented by Phar Lap, but it was Tenberry Software, Inc.'s (formerly Rational Systems) 386 extender DOS/4GW that brought protected mode DOS programs to the masses. Included with Watcom's C, C++ and Fortran compilers for 386 class processors, it soon became a ubiquitous mainstay of PC games and applications such as id Software's successful game DOOM. Image File history File links No higher resolution available. ...
Image File history File links No higher resolution available. ...
Phar Lap was a software company specializing in software development tools for the MS-DOS/PC-DOS operating systems. ...
DOS/4GW is the most widely used 32-bit DOS extender, designed to allow DOS programs to eliminate the inherent DOS 640KB memory limit by addressing all the extended memory on Intel 80386 and above machines in MS-DOS, PC-DOS, DR-DOS, the DOS boxes of OS/2, Windows...
Watcom International Corporation was founded in 1981 from the research of the Computer Systems Group at the University of Waterloo, in Waterloo, Ontario, Canada. ...
id Software (IPA: officially, though originally ) is an American computer game developer based in Mesquite, Texas, a suburb of Dallas. ...
This article is about the game. ...
While initially it was the memory hungry business applications that drove the development of DOS extenders, it would be PC games that truly brought them into the spotlight. As a result of the development of DOS extenders, two new software interfaces were created to take care of the many potential conflicts that could arise from the varied methods of memory management that already existed, as well as provide a uniform interface for client programs.
The first of these interfaces was the Virtual Control Program Interface, but this was rapidly overshadowed by the DOS Protected Mode Interface Specification, which grew from the Windows 3.0 development. [1] They provided an API through which an extended program could interface with real mode software, allocate memory, and handle interrupt services. They also provided an easy method for the extender to set up the switch to protected mode, and allowed multiple protected mode programs to coexist peacefully. DPMI is the method which Microsoft prescribes for a DOS program to run in protected mode and to access extended memory under a multitasking operating system like Microsoft Windows. ...
DPMI is the method which Microsoft prescribes for a DOS program to run in protected mode and to access extended memory under a multitasking operating system like Microsoft Windows. ...
Obsolescence With release of Microsoft Windows 95 DOS extender popularity began to decline, with Windows providing much of the same functionality that drove people to create DOS extenders in the first place (the ever increasing memory requirements of modern software). With the release of Windows 2000 (Windows NT v5.0), Microsoft finally shed the few remaining vestiges of MS-DOS that remained in their consumer operating systems. DOS extenders, once a hot technology, became a minority product. In spite of the decline in both popularity and use of MS-DOS and compatible operating systems, a few DOS extender writers have continued development. Many modern DOS extenders have further enhanced the concept of the DOS extender by providing emulation for some of the functionality provided by Windows, enabling some console mode applications, and even some applications that use other features of Windows (such as the GUI), to run on DOS. Windows 2000 (also referred to as Win2K) is a preemptive, interruptible, graphical and business-oriented operating system designed to work with either uniprocessor or symmetric multi-processor computers. ...
It has been suggested that this article or section be merged into cmd. ...
GUI can refer to the following: GUI is short for graphical user interface, a term used to describe a type of interface in computing. ...
Notable DOS extenders DOS/4GW is the most widely used 32-bit DOS extender, designed to allow DOS programs to eliminate the inherent DOS 640KB memory limit by addressing all the extended memory on Intel 80386 and above machines in MS-DOS, PC-DOS, DR-DOS, the DOS boxes of OS/2, Windows...
Phar Lap was a software company specializing in software development tools for the MS-DOS/PC-DOS operating systems. ...
Tomasz (aka Thomas) Pytel is a Polish-American programmer, better known as Tran / Renaissance in the demoscene. ...
PMODE is a DOS extender used in several IBM PC compatible DOS applications in the mid and late 1990s. ...
The demoscene is a computer art subculture that specializes itself on producing demos, non-interactive audio-visual presentations, which are run real-time on a computer. ...
1. ...
HX DOS-Extender is a free DOS extender with built-in Win32 PE file format support. ...
DPMI is the method which Microsoft prescribes for a DOS program to run in protected mode and to access extended memory under a multitasking operating system like Microsoft Windows. ...
DJ Delorie is a US-American software developer. ...
The GNU Compiler Collection (usually shortened to GCC) is a set of programming language compilers produced by the GNU Project. ...
DJGPP is a 32-bit C/C++/ObjC/Ada/Fortran development suite for 386+ PCs that runs under DOS (or any OS that runs DOS . ...
DJ Delorie is a US-American software developer. ...
The GNU Compiler Collection (usually shortened to GCC) is a set of programming language compilers produced by the GNU Project. ...
The FreePascal IDE for Linux. ...
Notable DOS extended applications AutoCAD is a CAD software application for 2D and 3D design and drafting, developed and sold by Autodesk, Inc. ...
Lotus 1-2-3 is a spreadsheet program from Lotus Software (now part of IBM). ...
Oracle Corporation (NASDAQ: ORCL) is one of the major companies developing database management systems (DBMS), tools for database development, middle-tier software, enterprise resource planning software (ERP), customer relationship management software (CRM) and supply chain management (SCM) software. ...
For other uses, see IBM (disambiguation) and Big Blue. ...
Founded in 1981, Interleaf was a company that produced a technical publishing software product with the same name. ...
The Major BBS (later renamed Worldgroup) was developed by Tim Stryker and launched in 1985 as the flagship product of Tims newly formed company called Galacticomm. ...
A bulletin board system or BBS is a computer system running software that allows users to dial into the system over a phone line and, using a terminal program, perform functions such as downloading software and data, uploading data, playing games, reading news, and exchanging messages with other users. ...
Phar Lap was a software company specializing in software development tools for the MS-DOS/PC-DOS operating systems. ...
Quarterdeck Office Systems, later Quarterdeck Corporation, was an American computer software company. ...
DESQview was a text mode multitasking program developed by Quarterdeck Office Systems which enjoyed modest popularity in the late 1980s and early 1990s. ...
Watcom International Corporation was founded in 1981 from the research of the Computer Systems Group at the University of Waterloo, in Waterloo, Ontario, Canada. ...
C is a general-purpose, block structured, procedural, imperative computer programming language developed in 1972 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system. ...
C++ (pronounced see plus plus, IPA: ) is a general-purpose programming language with high-level and low-level capabilities. ...
Fortran (previously FORTRAN[1]) is a general-purpose[2], procedural,[3] imperative programming language that is especially suited to numeric computation and scientific computing. ...
A diagram of the operation of a typical multi-language, multi-target compiler. ...
x86 or 80x86 is the generic name of a microprocessor architecture first developed and manufactured by Intel. ...
For the band, see 1990s (band). ...
id Software (IPA: officially, though originally ) is an American computer game developer based in Mesquite, Texas, a suburb of Dallas. ...
This article is about the game. ...
Zombies attacking the player at the starting of Episode 1, Mission 3: The Necropolis. ...
DJGPP is a 32-bit C/C++/ObjC/Ada/Fortran development suite for 386+ PCs that runs under DOS (or any OS that runs DOS . ...
Looking Glass Studios was a computer game development company during the 1990s. ...
For the Doctor Who novel, see System Shock (Doctor Who). ...
Parallax Software is the Midwest game developer who created the Descent [1] series. ...
Descent is a 3D first-person shooter video game which spawned two direct sequels (Descent II and Descent³). The Descent name was also used for an unrelated space simulator released by Volition, Inc. ...
Abuse is a run and gun computer game developed by Crack dot Com, and published by Origin Systems/Electronic Arts. ...
Blizzard Entertainment, a division of Vivendi Games, is an American computer game developer and publisher headquartered in Irvine, California. ...
The original box art for Warcraft: Orcs & Humans. ...
Warcraft II: Tides of Darkness (usually simply called Warcraft II; sometimes abbreviated to WCII or WC2) is a sequel to the popular real-time strategy game Warcraft, published by Blizzard Entertainment in December 1995. ...
3D Realms is the name of a computer game publisher and developer based in Garland, Texas. ...
Duke Nukem 3D is a first-person shooter computer game developed by 3D Realms and published by Apogee Software. ...
References - ^ Duncan, Ray (1992). Extending DOS: A Programmer's Guide to Protected-Mode DOS, 2nd ed., Addison-Wesley, pp. 433-462. ISBN 0-201-56798-9.
- ^ Williams, Al (1993). DOS and Windows Protected Mode: Programming with DOS Extenders in C. Addison-Wesley, pp. 30. ISBN 0-201-63218-7.
Pearson can mean Pearson PLC the media conglomerate. ...
Pearson can mean Pearson PLC the media conglomerate. ...
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