The Add Two Multiple-Precision Binary Numbers routine adds two
    signed two's complement integers of arbitrary length.

    Format

      LIB$ADDX  addend-array ,augend-array ,resultant-array

                [,array-length]

1  –  Returns

    OpenVMS usage:cond_value
    type:         longword (unsigned)
    access:       write only
    mechanism:    by value

2  –  Arguments

 addend-array

    OpenVMS usage:vector_longword_signed
    type:         unspecified
    access:       read only
    mechanism:    by reference, array reference

    First multiple-precision, signed two's complement integer that
    LIB$ADDX adds to the second two's complement integer. The addend-
    array argument is the address of the array containing the two's
    complement number to be added.

 augend-array

    OpenVMS usage:vector_longword_signed
    type:         unspecified
    access:       read only
    mechanism:    by reference, array reference

    Second multiple-precision, signed two's complement integer that
    LIB$ADDX adds to the first two's complement integer. The augend-
    array argument is the address of the array containing the two's
    complement number.

 resultant-array

    OpenVMS usage:vector_longword_signed
    type:         unspecified
    access:       write only
    mechanism:    by reference, array reference

    Multiple-precision, signed two's complement integer result of
    the addition. The resultant-array argument is the address of the
    array into which LIB$ADDX writes the result of the addition.

 array-length

    OpenVMS usage:longword_signed
    type:         longword integer (signed)
    access:       read only
    mechanism:    by reference

    Length in longwords of the arrays to be operated on; each array
    is of length array-length. The array-length argument is the
    address of a signed longword integer containing the length. The
    array-length argument must not be negative. This is an optional
    argument. If omitted, the default is 2.