2 ms·

The real-mode DOS system call interface is based on loading a function number into the AH register, other arguments in other registers, and calling interrupt 21

The real-mode DOS system call interface is based on loading a function number into the AH register, other arguments in other registers, and calling interrupt 21h. I haven't used CP/M before, but it sounds like the DOS function numbers must be numbered in a similar fashion as their CP/M equivalents. Edit: This list of BDOS system calls bears a passing resemblance, based on my foggy memory, to some of the interrupt 21h calls I remember: http://www.seasip.info/Cpm/bdos.html http://www.seasip.info/Cpm/bdos.html The conventions with arguments in registers is different, however.

linker3000 10y ago
From a link I posted in response to another comment about the calls: [SNIP] ;********************************************************** ;* * ;* Get the time from DOS * ;* * ;********************************************************** MOV AH,2CH ;Set up DOS call to get the current time INT 21H ;And go get it! [SNIP] MOV AX,04C00 ;Return to DOS INT 21H