INT 15H 85H: SysReq Key
Expects: AH 85H
AL 00H = key make (pressed down)
01H = key break (released)
CF NC (0)
Returns: AX 0085H
CF NC (0) if no error; CY (1) if invalid value in AL on entry
Info: Called by INT 01H upon press and release of the SysReq key.
A multitasking operating system might intercept this fn in order
to monitor user-requests to switch tasks.
When unintercepted, the BIOS simply sets AH to 0 and clears CF.
See Also: INT 15H (extended AT services)
BIOS Data Area