{
{    The purpose of this request is to open a file for segment access and
{  associate it with a previously defined unallocated common block.
{
{        PMP$OPEN_COMMON_BLOCK_FILE (FILE, COMMON_BLOCK, SEGMENT_POINTER,
{          STATUS)
{
{  FILE: (input) This paramener specifies the path name of the file to be
{        opened.  The value specified will be evaluated by this request as
{        an SCL <file expression>.
{
{  COMMON_BLOCK: (input) This parameter specifies the name of a previously
{        defined unallocated common block.  This common block cannot be
{        associated with a file at the time this request is issued.
{
{  SEGMENT_POINTER: (output) This parameter specifies a segment pointer to
{        the common block/file.
{
{  STATUS: (output) This parameter specifies the request status.
{        CONDITIONS:
{              pme$common_file_open
{              pme$common_not_unallocated
{
