Source : Free On-Line Dictionary of Computing

US-ASCII
     
         The 7-bit version of {ASCII}, which preceded (and
        is the basis for) 8-bit versions such as {Latin-1}, {MacASCII}
        and later, even larger coded character sets such as {Unicode}.
     
        US-ASCII is defined in Standard ANSI X3.4-1986,
        "US-ASCII. Coded Character Set - 7-Bit American Standard Code
        for Information Interchange".
     
        (1998-10-18)