context

    OpenVMS usage:context
    type:         longword (unsigned)
    access:       read only
    mechanism:    by reference
    Value identifying the data stream that DCX$EXPAND_DATA expands.
    The context argument is the address of a longword containing this
    value. DCX$EXPAND_INIT initializes this value; you should not
    modify it. You can define multiple context arguments to identify
    multiple data streams that are processed simultaneously.

 in_rec

    OpenVMS usage:char_string
    type:         character string
    access:       read only
    mechanism:    by descriptor
    Data record to be expanded. The in_rec argument is the address of
    the descriptor of the data record string.

 out_rec

    OpenVMS usage:char_string
    type:         character string
    access:       write only
    mechanism:    by descriptor
    Data record that has been expanded. The out_rec argument is the
    address of the descriptor of the expanded record returned by
    DCX$EXPAND_DATA.

 out_length

    OpenVMS usage:word_signed
    type:         word integer (signed)
    access:       write only
    mechanism:    by reference
    Length (in bytes) of the expanded data record. The out_length
    argument is the address of a word into which DCX$EXPAND_DATA
    returns the length of the expanded data record.