Source : Free On-Line Dictionary of Computing

first generation computer
     
         A prototype computer based on {vacuum tubes}
        and other esoteric technologies.  Chronologically, any
        computer designed before the mid-1950s.  Examples include
        {Howard Aiken}'s {Mark 1} (1944), Maunchly and Eckert's
        {ENIAC} (1946), and the {IAS} computer.
     
        (1996-11-22)