Source : Free On-Line Dictionary of Computing

Pulse Code Modulation
     
         (PCM) A method by which an audio signal is represented
        as digital data.
     
        Virtually all digital audio systems use PCM, including, {CD},
        {DAT}, F1 format, 1630 format, DASH, DCC, and MD.  Many people
        get confused because "PCM" is also slang for Sony's F1 format
        which stores PCM digital audio on videotape.
     
        (1995-02-09)