/sys$common/syshlp/helplib.hlb EXIT, Parameter  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 status-code

    Defines a numeric value for the reserved global symbol $STATUS.
    You can specify the status-code parameter as an integer or an
    expression equivalent to an integer value. The value can be
    tested by the next outer command level. The low-order 3 bits
    of the value determine the value of the global symbol $SEVERITY.

    If you specify a status code, DCL interprets the code as a
    condition code. Note that even numeric values produce warning,
    error, and fatal error messages, and that odd numeric values
    produce either no message or a success or informational message.

    If you do not specify a status code, the current value of $STATUS
    is saved. When control returns to the outer command level,
    $STATUS contains the status of the most recently executed command
    or program.