Click above to get retro games delivered to your door ever month!

  When the main byte is an ASCII character value from 01H to FFH, one of two
  events has occurred: One of the standard keyboard characters was pressed,
  or an ASCII character was entered directly using the Alt-number method
  mentioned above. (See Appendix C for the complete ASCII character set.)
  For these ASCII characters, the auxiliary byte contains the scan code of
  the pressed key. (The scan code is 0 for characters entered with
  Alt-number.) Usually you can ignore this scan code. DOS does not report
  keyboard scan codes, nor do high-level programming language functions like
  getch() in C or INKEY$ in BASIC. However, a program can examine the
  auxiliary byte (scan code) to differentiate among duplicate keyboard
  characters.