[XT] [AT]
Expects: AH    4fH
AL    keyboard scan code received from hardware
CX    process ID
                                                                  
Returns: AL    keyboard scan code
CF = CY: replace input scan code with the one on AL
CF = NC: no change; use hardware scan code
                                                                  
Info: This fn is called by INT 09H when it obtains a keystroke from the
hardware, but before processing it or placing it in the keyboard
buffer.

Programs can intercept this fn to provide keyboard remapping or
to disable certain keystrokes, etc.

When unintercepted, the BIOS simply leaves the CF clear so
INT 09H will process the scan code without change.

Notes: This intercept is available only in later versions of XT and AT
BIOSes.  Use INT 15H c0H to see if this intercept is available.

See Also: INT 15H (extended AT services)
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INT 15H 4fH: Keyboard Intercept