Source : Free On-Line Dictionary of Computing

HAL
     
        1.  HAL 9000, the murdering computer on the
        spaceship in the science fiction classic "2001, A Space
        Odyssey" by Arthur C. Clark.
     
        "HAL" is "{IBM}" with each letter changed to the one before
        and there is an unconfirmed rumour that 9000 is the sum of the
        various IBM computer numbers that were in service at the time.
        However, in the sequel "2010", Clarke emphatically denies that
        HAL's name is supposed to be "one step ahead of IBM".  It is,
        rather, short for "heuristic algorithm".
     
        2.  {Hardware Abstraction Layer}.
     
        (1995-11-09)