The OpenVMS LDAP API supports both 32- and 64-bit client
    applications. In order to allow this, separate entry points are
    provided in the library for those functions that are sensitive to
    pointer size.

    When a user module is compiled, the header file LDAP.H determines
    the pointer size in effect and uses the C preprocessor to map
    the function names into the appropriate library entry point. This
    mapping is transparent to the user application and is effected by
    setting the /POINTER_SIZE qualifier at compilation time.

    For LDAP API users, switching between different pointer sizes
    should need only a recompilation-no code changes are necessary.

    This means that programs using the specification for the C LDAP
    API, as described in the Internet Engineering Task Force (IETF)
    documentation, can be built on OpenVMS with either 32-bit or
    64-bit pointer size, without having to change the source code.