Function 33h (51)        Get or Set Ctrl-Break Status

Reports the status of or sets extended Ctrl-Break checking.

On entry:      AH         33h
AL         00h      to get BREAK state
AL         01h      to set BREAK state
DL         00h      to set BREAK OFF
01h      to set BREAK ON

Returns:       DL         00h      BREAK is OFF
01h      BREAK is ON


With DOS versions 2.00 and later, Ctrl-Break checking can be extended
to take place any time input or output is requested via DOS. (DOS
normally acts on Ctrl-Break only under a limited set of
circumstances  during certain keyboard and screen functions.) Use
Function 33h to toggle extended Ctrl-Break monitoring on or off.

Note:          The default for Ctrl-Break monitoring is off.

The state of the control break flag can be set at
the DOS prompt with the "break on" command, so it is
a nice idea to save the state of the break flag and
restore it before returning to DOS.

33h (51) Get or Set Ctrl-Break Status