02/06/84  pl1_io_

The pl1_io_ subroutine is a collection of utility functions for
extracting information about PL/I files that is not available within
the language itself.


Entry points in pl1_io_:
   (List is generated by the help command)


:Entry:  error_code:  02/06/84 pl1_io_$error_code


Function: returns the last nonzero status code encountered by PL/I I/O
while performing file operations.  This is a standard Multics status
code and describes the most recent error more specifically than the
PL/I condition which is raised after an error.


Syntax:
declare pl1_io_$error_code entry (file) returns (fixed bin(35));
code = pl1_io_$error_code (file_variable);


Arguments:
file_variable
   is a PL/I file value.  (Input)
code
   is the last nonzero status code associated with the file.  (Output)


Notes:  The specific values returned by this function are subject to
change.  See "Handling Unusual Occurrences" in the Programmer's
Reference Manual.


:Entry:  get_iocb_ptr:  02/06/84 pl1_io_$get_iocb_ptr


Function: returns the I/O control block pointer for the Multics I/O
System switch associated with an open PL/I file.  This pointer may be
used to perform control and modes operations upon the switch
associated with that file.


Syntax:
declare pl1_io_$get_iocb_ptr entry (file) returns (ptr);
iocb_ptr = pl1_io_$get_iocb_ptr (file_variable);


Arguments:
file_variable
   is a PL/I file value.  (Input)
iocb_ptr
   is a pointer to the I/O control block for the file.  (Output)


Notes:  Performing explicit operations via the Multics I/O System upon
switches in use by PL/I I/O is potentially dangerous unless care is
taken that certain conventions are observed.  No calls should be made
that affect the data in the PL/I data set being accessed, the
positioning of the data set, or the status or interpretation of any I/O
operations that may be in progress.  In general, this limits such calls
to those which obtain status information.


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Historical Background

This edition of the Multics software materials and documentation is provided and donated
to Massachusetts Institute of Technology by Group BULL including BULL HN Information Systems Inc. 
as a contribution to computer science knowledge.  
This donation is made also to give evidence of the common contributions of Massachusetts Institute of Technology,
Bell Laboratories, General Electric, Honeywell Information Systems Inc., Honeywell BULL Inc., Groupe BULL
and BULL HN Information Systems Inc. to the development of this operating system. 
Multics development was initiated by Massachusetts Institute of Technology Project MAC (1963-1970),
renamed the MIT Laboratory for Computer Science and Artificial Intelligence in the mid 1970s, under the leadership
of Professor Fernando Jose Corbato. Users consider that Multics provided the best software architecture 
for managing computer hardware properly and for executing programs. Many subsequent operating systems 
incorporated Multics principles.
Multics was distributed in 1975 to 2000 by Group Bull in Europe , and in the U.S. by Bull HN Information Systems Inc., 
as successor in interest by change in name only to Honeywell Bull Inc. and Honeywell Information Systems Inc. .

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Permission to use, copy, modify, and distribute these programs and their documentation for any purpose and without
fee is hereby granted,provided that the below copyright notice and historical background appear in all copies
and that both the copyright notice and historical background and this permission notice appear in supporting
documentation, and that the names of MIT, HIS, BULL or BULL HN not be used in advertising or publicity pertaining
to distribution of the programs without specific prior written permission.
    Copyright 1972 by Massachusetts Institute of Technology and Honeywell Information Systems Inc.
    Copyright 2006 by BULL HN Information Systems Inc.
    Copyright 2006 by Bull SAS
    All Rights Reserved