Interesting, didn't know that there were 4 groups. I do remember INT 21H and setting a value in a register to specify what syscall you want run. Turbo Pascal ha

Interesting, didn't know that there were 4 groups. I do remember INT 21H and setting a value in a register to specify what syscall you want run. Turbo Pascal had some support for assembly and even register handling, IIRC, so you could write such low-level programs in it. Also had absolute memory addressing which could be used for anything where you need to manipulate fixed, known memory addresses, such as video RAM.