en:docs:dos:api

This is an old revision of the document!


DOS API

Most of DOS API calls are invoked using software interrupt INT 21H. In most cases AH register sets to function number.

DOS Interrupts

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
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

en/docs/dos/api.1536291218.txt.gz · Last modified: 2018/09/07 05:33 by prokushev