VMS Help MACRO, /MIGRATION, Macros for 64-Bit Addressing, $IS DESC64  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Tests the specified descriptor to determine if it is a 64-bit
    format descriptor, and directs the program flow based on the
    outcome of the test.

    Format

      $IS_DESC  desc_addr, target, size=long or quad

  Additional Information (explode) :

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