source-string
    OpenVMS usage:char_string
    type:         character string
    access:       read only
    mechanism:    by descriptor
    Source string used by LIB$SCANC to index into a table. The
    source-string argument contains the address of a descriptor
    pointing to this source string.
 table-array
    OpenVMS usage:vector_mask_byte
    type:         byte (unsigned)
    access:       read only
    mechanism:    by reference, array reference
    Table that LIB$SCANC indexes into and performs a logical AND
    operation with the byte-integer-mask byte. The table-array
    argument contains the address of an unsigned byte array that
    is this table.
 byte-integer-mask
    OpenVMS usage:mask_byte
    type:         byte (unsigned)
    access:       read only
    mechanism:    by reference
    Mask on which a logical AND operation is performed with bytes in
    table-array. The byte-integer-mask argument contains the address
    of an unsigned byte that is this mask.