VMS Help RTL Routines, LIB$, LIB$INSV  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    The Insert a Variable Bit Field routine replaces the variable bit
    field specified by the base, position, and size arguments with
    bits 0 through (size-1) of the source field. If the size of the
    bit field is zero, nothing is inserted. LIB$INSV makes the VAX
    INSV instruction available as a callable routine.

    Format

      LIB$INSV  longword-integer-source ,position ,size ,base-address

1 - Returns

    None.

2 - Arguments

 longword-integer-source

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

    Source field to be inserted by LIB$INSV. The  longword-integer-
    source argument is the address of a signed longword integer that
    contains this source field.

 position

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

    Bit position relative to the base address where insertion of
    longword-integer-source is to begin. The position argument is
    the address of a longword integer that contains this relative bit
    position.

 size

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

    Size of the bit field to be inserted by LIB$INSV. The size
    argument is the address of an unsigned byte that contains the
    size of this bit field. The maximum size is 32 bits.

 base-address

    OpenVMS usage:address
    type:         address
    access:       read only
    mechanism:    by value

    Field into which LIB$INSV writes the source field. The base-
    address argument is an unsigned longword containing the base
    address of this aligned bit string.