INT 21,E - Select Disk

AH = 0E

DL = zero based, drive number (0-25, A: - Z:)

on return:

AL = one based, total number of logical drives including

hardfiles (1-26)

- for DOS 3.x+, this function returns the number of logical

drives or the value of LASTDRIVE (default of 5) in the

CONFIG.SYS file