DOS API
Interrupt vectors used by DOS
The following is the list of interrupt vectors used by programs to invoke the DOS API functions.

DOS API

Section Title: Interrupt vectors used by DOS
Table Section Text: The following is the list of interrupt vectors used by programs to invoke the DOS API functions.

Interrupt vector	Description	Version	Notes

20h	Terminate program	1.0+	Implemented in DOS kernel

21h	Main DOS API	1.0+	Implemented in DOS kernel

22h	Program terminate address	1.0+	Return address in calling program

23h	Control-C handler address	1.0+	Default handler is in the command shell (usually COMMAND.COM)

24h	Critical error handler address	1.0+	Default handler is in the command shell (usually COMMAND.COM)

25h	Absolute disk read	1.0+	Implemented in DOS kernel, enhanced in DOS 3.31 to support up to 2 GB partitions

26h	Absolute disk write	1.0+	Implemented in DOS kernel, enhanced in DOS 3.31 to support up to 2 GB partitions

27h	Terminate and stay resident	1.0+	Implemented in COMMAND.COM in DOS 1.0, DOS kernel in DOS 2.0+

28h	Idle callout	2.0+	Called by DOS kernel when waiting for input

29h	Fast console output	2.0+	Implemented by the builtin console device driver or a replacement driver like ANSI.SYS

2Ah	Networking and critical section	3.0+	Called by DOS kernel to interface with networking software

2Bh	Unused

2Ch	Unused

2Dh	Unused

2Eh	Reload transient	2.0+	Implemented in COMMAND.COM

2Fh	Multiplex	3.0+	Implemented in DOS kernel and various programs (PRINT, MSCDEX, DOSKEY, APPEND, etc.) depending on subfunction number

Sentence(s)

In DOS 3.31, the INT 25h/26h functions were enhanced to support hard disks greater than 32 MB.
In DOS 3.31, the INT 25h/26h functions are enhanced.

final_sentence: In DOS 3.31, the INT 25h/26h functions were enhanced to support hard disks greater than 32 MB.
final_sentence: In DOS 3.31, the INT 25h/26h functions are enhanced.