INT 1bH: Keyboard Break

 This vector (0:006c) is taken by BIOS when it senses a press of the

 Ctrl-Break key.

 INT 1bH initially points to an IRET, but DOS sets it to point to local

 code that sets an internal DOS flag.  DOS tests every once in a while and

 acts upon it, depending upon the state of DOS break-testing.

 See DOS Fn 33H and INT 23H for descriptions of how DOS handles Ctrl-Break.

 A flag in the BIOS Data Area (0:0471) gets set upon the first occurrence

 of Ctrl-Break, but it never gets reset unless you do it yourself.  You

 might use this flag as a way to determine if a child process was aborted

 via Ctrl-Break.

See Also: DOS Interrupts

          ROM-BIOS Functions