The Extract a Zero-Extended Field routine returns a longword
    zero-extended field that has been extracted from the specified
    variable bit field. LIB$EXTZV makes the VAX EXTZV instruction
    available as a callable routine.

    Format

      LIB$EXTZV  position ,size ,base-address

1  –  Returns

    OpenVMS usage:longword_signed
    type:         longword integer (signed)
    access:       write only
    mechanism:    by value

    Field extracted by LIB$EXTZV, zero-extended to a longword.

2  –  Arguments

 position

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

    Position (relative to the base address) of the first bit in the
    field LIB$EXTZV extracts. The position argument is the address of
    a signed longword integer containing the position.

 size

    OpenVMS usage:byte_unsigned
    type:         byte (unsigned)
    access:       read only
    mechanism:    by reference

    Size of the bit field LIB$EXTZV extracts. The size argument is
    the address of an unsigned byte containing the size. The maximum
    size is 32 bits.

 base-address

    OpenVMS usage:longword_unsigned
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value

    Base address of the bit field LIB$EXTZV extracts. The base-
    address argument is an unsigned longword containing the base
    address.