INT 15h,  4Fh (79)       Keyboard Intercept                              many

    Called by the hardware keyboard handler (INT 09h), allowing the
    replacement or removal of a key.

       On entry:      AH         4Fh
                      AL         Scan code

       Returns:       Carry      Cleared if scan code removed, else set
                      AL         New scan code if changed, else original scan
                                 code

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    Upon entry to this service, AL will contain the scan code of the
    keystroke. If the user wishes to change the scan code, put the new
    scan code in AL and set the Carry Flag. If the scan code is to remain
    the same, then leave AL alone and set the Carry Flag. The user can
    remove or ignore the keystroke by returning with the Carry Flag clear.

       Notes:         This service is not available for the PC, PCjr, XT
                      dated 11/08/82, and the AT dated 1/10/84.

                      By writing a handler for this service, the user can
                      change the meaning of a key. The operating system
                      normally will return the scan code unchanged (that
                      is, it will leave AL alone and return with the Carry
                      Flag set).

                      To determine the machines that support this feature,
                      see Service C0h (Return System Configuration).