DOS API: Difference between revisions

Revision as of 20:47, 18 May 2008

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The '''MS-DOS API''' is an [[API]] used in [[MS-DOS]], [[PC-DOS]] and other compatible operating systems. The DOS API is based on software interrupt 21h (int 21h). By calling int 21h with the subfunction in ahAH and the other parameters in other registers, one invokes various DOS services. DOS services include keyboard input, video output, disk file access, executing programs, memory allocation, and various other things. There are various implementations of the DOS API, including MS-DOS, PC-DOS, DR-DOS, FreeDOS, PTS-DOS, and others. The DOS API is based on the [[BIOS]], and [[DOS]] routines often internally access [[BIOS interrupt call]]s.

[[Microsoft Windows]] versions 1.0 through 3.1 were graphical shells that ran on MS-DOS and relied on the MS-DOS API. [[Windows 9x]] was also DOS based, but used a custom version of MS-DOS mainly as a bootloader and did not use the MS-DOS API much after booting. [[Windows NT]] is not based on MS-DOS, but features a DOS emulator called [[NTVDM]]. NTVDM works by running a DOS program in [[virtual 8086 mode]] (an emulation of [[real mode]] within [[protected mode]] available on [[80386]] and higher processors). [[DOSEMU]] for [[linux]] uses a similar approach.