Int 21H, AH=33H, AL=02H

3.0 and higher

GET AND SET EXTENDED CONTROL-BREAK CHECKING STATE

      AX = 3302h
      DL = new state (00h for OFF, 01h for ON)

DL = old state of extended BREAK checking

this function does not use any of the DOS-internal stacks and may thus
        be called at any time; one possible use is modifying Control-Break
        checking from within an interrupt handler or TSR
      not supported by DR DOS through version 6.0 (error code 01h);
        newly-supported by Novell DOS 7

AH=33h

Text based on Ralf Brown Interrupt List Release 61