INT 16H 00H: Read (Wait for) Next Keystroke

                                                                   [XT] [AT]
 Expects: AH    00H
 Returns: AH    scan code
          AL    ASCII character code or extended ASCII keystroke
    Info: If a keystroke is available in the keyboard buffer, this removes
          it from the queue and returns it in AH and AL.

          If no key is available, this waits for a keystroke.  If you want
          to avoid the wait, use INT 16H 01H to see if a key is ready.

   Notes: ■ On ATs, when the keyboard buffer is empty, this invokes
            INT 15H 90H, allowing an operating system to switch tasks or
            whatever, when awaiting a keystroke.

          ■ Also on ATs, this updates the keyboard LEDs to match the
            current shift status.

          ■ Extended key filtering: For compatibility with older 83-key
            'boards, this converts duplicated keys into their older
            equivalent keys.  Use INT 16H 10H to get unfiltered key codes.

See Also: INT 16H (BIOS keyboard services)
          BIOS Data Area
          ROM-BIOS Functions