VMS Help MACRO, /MIGRATION, Page-Related Calculations, $ROUND RETADR, Parameters  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 retadr

    Address of array of two 32-bit addresses, typically returned from
    $CRMPSC or a similar service. This value can be in the form of
    either "label" or "(Rx)".

 full_range

    Output array of two longwords. FULL_RANGE[0] is retadr[0]
    rounded down to a CPU-specific page boundary, and FULL_RANGE[1]
    is retadr[1] rounded up to one less than a CPU-specific page
    boundary (that is, to the last byte in the page).

 user_mask_addr

    Location of application-provided byte-within-page mask. If this
    argument is blank, the macro uses MMG$GL_BWP_MASK on an OpenVMS
    Alpha system and VA$M_BYTE on an OpenVMS VAX system.

 direction=ASCENDING

    Direction of rounding. The keywords are defined in the following
    table:

    ASCENDING          retadr[0] < retadr[1]
    DESCENDING         retadr[1] < retadr[0]
    UNKNOWN            Values are compared at run time, then proper
                       rounding is performed