INT 21 - DOS 2+ - EXTENDED BREAK CHECKING
AH = 33h
AL = subfunction
00h get current extended break state
Return: DL = current state, 00h = off, 01h = on
01h set state of extended ^C/^Break checking
DL = 00h off, check only on character I/O functions
01h on, check on all DOS functions
Note:   under DOS 3.1+, this function does not use any of the DOS-internal and
may thus be called at any time

See also: 213302

2133 - DOS 2+ - EXTENDED BREAK CHECKING