Source : Free On-Line Dictionary of Computing

Vertical Redundancy Check
     
         (VRC) An {error checking} method
        performed on one 8-bit {ASCII} character, where the 8th bit is
        used as the {parity bit}.
     
        The resulting parity bit is constructed by {XOR}ing the
        {word}.  The result is a "1" if there is an odd number of 1s,
        and a "0" if there is an even number of 1s in the word.  This
        method is unreliable because if an odd number of {bits} are
        distorted, the check will not detect the error.  The
        {Longitudinal Redundancy Check} is an improvement.
     
        (2001-04-28)