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 3.0 and later. This service is called the DPMI host. It is provided either by the host operating system (virtual DPMI host) or by 16-bit or 32-bit DOS extenders such as DOS4GW or CWSDPMI (real DPMI host). Microsoft Corporation (NASDAQ: MSFT, SEHK: 4338) is an international computer technology corporation has global annual sales of over 41. ... ‹ The template below has been proposed for deletion. ... Protected mode is an operational mode of x86-compatible CPUs of the 80286 series or later. ... Extended memory refers to memory above the first megabyte of address space in an IBM PC with an 80286 or later processor. ... In computing, multitasking is a method by which multiple tasks, also known as processes, share common processing resources such as a CPU. In the case of a computer with a single CPU, only one task is said to be running at any point in time, meaning that the CPU is... An operating system (OS) is an essential software program that manages the hardware and software resources of a computer. ... Microsoft Windows is a series of proprietary operating environments and operating systems created by Microsoft for use on personal computers and servers. ... DOS extender is the name invented in the 1980s for a technology to allow programs started from MS-DOS, which ran in Real mode, to actually run in protected mode. ... 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...

The DPMI specification version 0.9 was published in 1990 by the DPMI Committee, and it was extended to version 1.0 in 1991. It is available from Intel Literature Sales. However, version 1.0 was never implemented in Windows so programs have to be written to version 0.9. This article is about the year. ... 1991 (MCMXCI) was a common year starting on Tuesday of the Gregorian calendar. ... Intel Corporation (NASDAQ: INTC, SEHK: 4335), founded in 1968 as Integrated Electronics Corporation, is a U.S.-based multinational corporation that is best known for designing and manufacturing microprocessors and specialized integrated circuits. ...

VCPI

VCPI (Virtual Control Program Interface) was an earlier and incompatible method for doing the same thing. It was limited to 32-bit mode. VCPI was provided by the expanded memory manager in DOS (e.g. CEMM, QEMM, later EMM386). It got eclipsed by DPMI, notably because it was not supported for DOS programs run in Windows 3.0's most powerful 386 enhanced mode. It also did not work with OS/2 2.0 and later. Windows 3.0 only supported VCPI in Standard and Real modes. Earlier Windows/386 2.1 was not compatible with DOS extenders at all. // Overview Expanded Memory was a trick invented around 1984 in order to offer more memory to memory-hungry business-oriented MS-DOS programs, typically spreadsheets and databases, running on the original IBM PC and on successors like the IBM AT, but still in compatibility real mode. ... CEMM, for Compaq Expanded Memory Manager was probably the first so-called PC memory manager for Intel 80386 CPUs, able to transform extended memory into EMS expanded memory by using the virtual memory features and the virtual 8086 mode of the CPU. It was present in Compaq DOS 3. ... QEMM, the Quarterdeck Expanded Memory Manager by Quarterdeck, was the most popular memory manager for the DOS operating system. ... EMM386 was Microsofts expanded memory manager, which created expanded memory using extended memory on Intel 80386 CPUs. ... OS/2 is an operating system created by Microsoft and IBM and later developed by IBM exclusively. ...

VCPI also had a more limited scope, in that it basically only allowed a protected mode DOS program to run at all when such a program was started from DOS already running inside a virtual 8086 mode task, typically because a memory manager was installed and operating as a virtual [mode] control program for the processor. Indeed, because the virtual 8086 mode fully isolates programs from the hardware, without some support from the control program, it is not possible for another program to switch to protected mode by itself. In the 80386 and later, Virtual 8086 mode, also called virtual real mode, allows the execution of real mode applications that violated the rules mentioned here under the control of a protected mode operating system. ... A memory manager is a part of a computer program which accepts requests from the program to allocate and deallocate chunks of memory. ...

External links

• DPMI Specification, version 1.0 (PDF)

This article was originally based on material from the Free On-line Dictionary of Computing, used with permission. Update as needed. The Free On-line Dictionary of Computing (FOLDOC) is an on-line, searchable encyclopedic dictionary of computing subjects. ...