Source : Free On-Line Dictionary of Computing

Control and Status Register
     
         (CSR) A {register} in most {CPU}s which stores
        additional information about the results of machine
        instructions, e.g. comparisons.  It usually consists of
        several independent flags such as {carry}, {overflow} and
        zero.  The CSR is chiefly used to determine the outcome of
        {conditional branch} instructions or other forms of
        conditional execution.
     
        (1998-06-26)