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

  Compares two objects, byte by byte.  The compare operation starts
  with the first byte in each object.  It returns an integer less
  than, equal to, or greater than 0, depending on whether the lexical
  value of the first object is less than, equal to, or greater than
  that of the second object.

  Syntax:

       #include <string.h>

       int memcmp (const void *s1, const void *s2, size_t size);