These are a few programs I wrote in real mode x86 assembly for MS-DOS. They don't really serve any practical purpose, I just wanted to have a go at writing some programs in assembly so here they are.
I run DOS inside VirtualBox on Mac OS, so I have some shell scripts to build a disk image etc. They probably run under Linux (or Cygwin) too, but haven't tried them.
Assuming you have mtools installed, just run ./build.sh. This will create a
1.44MB floppy image called Build/zutl.img. Now open that disk image in
MS-DOS, and run ASMALL.BAT (assumes nasm is in your path). This will assemble
all the programs.
Note that build wipes out your disk image, so if you edit the files on the
DOS side, you will lose all your changes if you run this. You can use
fromFloppy.sh to copy the changes from DOS back to Unix.
APMINFO- checks if APM BIOS is present, if so prints the APM versionDUMPARGS- prints out its own command line and the environment varsINTDUMP- dumps the interrupt vector table in hex formatPCTYPE- prints PC type stored in ROM BIOS. Meaningless value except on 1980s vintage IBM hardware.POWEROFF- uses APM to turn off the computer powerRS232MON- shows RS-232 status flags in real-time. (I'm not sure whether values it displays are actually correct.)RUNSHELL- runs a subshell (i.e. child COMMAND.COM instance)VCLS- clears the screenVMODE- displays or changes video modeVPAGE- displays or changes video pageVPAUSE- equivalent to the MS-DOSPAUSEcommandZUTL- displays various system information