
appendix d
list of dos and bios functions
In this, some of the DOS 21H functions and the BIOS 10H and 16H functions are listed.
i) List of important DOS INT 21H services
DOS system calls use the 21H vector. Some of the important INT 21H services are listed here.
Function No. Action Returns/Expects
AH = 01
Read character from standard input
device with echo
Returns:
AL = ASCII of the input key
AH = 02
Write character to standard output
device
Expects:
DL = ASCII code of output data
AH = 05
Write character to printer Expects:
DL = ASCII of the output
AH = 08
Read character input from standard
input device, without echo
Returns:
AL = ASCII of the input key
AH