🚀 go-pugleaf

You can get gobs of neat information from INT 21, AH=52.  To find the
number of block devices (drives) in a system, look at offset 20h from
the pointer returned by ES:BX.

Example:

#include <dos.h>

main()
{
        union REGS regs;
        struct SREGS sregs;
        unsigned char far *ptr;

        regs.h.ah = 0x52;
        intdosx(&regs, &regs, &sregs);

        ptr = (unsigned char far *) (((unsigned long) sregs.es<<16)+regs.x.bx);

        printf("Number of block devices: %d\n", (int) *(ptr+0x20));
        printf("Value of LASTDRIVE: %d\n", (int) *(ptr+0x21));

        return(0);
}