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

 Message        <Context> the right shift count "<number>" is greater
                than or equal to the size of the unpromoted operand
                "<expression>".

 Description    The compiler has detected a right shift count that is
                greater than or equal to the size of the operand to
                be shifted (before application of the integral
                promotions).  This might not be what you intended, as
                the result contains none of the original bits of the
                operand.  For an unsigned operand, the result is
                always 0.  For a signed operand, the result is either
                0 or -1, depending on whether or not the operand had
                a negative value.  The same result would be achieved
                by shifting a signed operand one fewer bits.

 User Action    Correct the shift count (or replace the expression by
                0 if appropriate).