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

    The Find First Clear or Set Bit routines search the field
    specified by the start position, size, and base for the first
    clear or set bit. LIB$FFC and LIB$FFS make the VAX FFC and VAX
    FFS instructions available as callable routines.

    Format

      LIB$FFC  position ,size ,base ,find-position

      LIB$FFS  position ,size ,base ,find-position

1 - Returns

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

2 - Arguments

 position

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

    Starting position, relative to the base address, of the bit field
    to be searched by LIB$FFx. The position argument is the address
    of a signed longword integer containing the starting position.

 size

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

    Number of bits to be searched by LIB$FFx. The size argument is
    the address of an unsigned byte containing the size of the bit
    field to be searched. The maximum size is 32 bits.

 base

    OpenVMS usage:address
    type:         longword (unsigned)
    access:       read only
    mechanism:    by reference

    The base argument is the address of the bit field that LIB$FFx
    searches.

 find-position

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

    Bit position of the first bit in the specified state (clear or
    set), relative to the base address. The find-position argument
    is the address of a signed longword integer into which LIB$FFC
    writes the position of the first clear bit and into which LIB$FFS
    writes the position of the first set bit.