INT 21,33 - Get/Set System Values (Ctl-Break/Boot Drive)

AH = 33h

AL = 00 to get Ctrl-Break checking flag

= 01 to set Ctrl-Break checking flag

= 02 to set extended Ctrl-Break checking

= 05 get boot drive (DOS 4.x)

DL = 00 to set Ctrl-Break checking off

= 01 to set Ctrl-Break checking on

= boot drive for subfunction 5; (1=A:, 2=B:, ...)

on return:

DL = 00 Ctrl-Break checking OFF (AL=0 or AL=2)

= 01 Ctrl-Break checking ON (AL=0 or AL=2)

= boot drive number (1-26, A: - Z:) (function 05)

- retrieves DOS Ctrl-Break or extended Ctrl-Break setting which

determines if DOS will check for Ctrl-Break during INT 21 calls