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

 source_va

    Source virtual address.

 dest_va

    Destination of virtual address of first byte within page.

 user_mask_addr

    Location of application-provided byte-within-page mask. If this
    argument is blank, the macro uses MMG$GL_BWP_MASK in OpenVMS
    Alpha systems and MMG$C-VAX-PAGE-SIZE - 1 (defined in $pagedef)
    in OpenVMS VAX systems.

 quad=YES

    If YES, the conversion supports 64-bit addressing. If NO, the
    conversion does not support 64-bit addressing.