02/25/85  signal_io_


The signal_io_ I/O module signals a condition whenever an iox_ I/O
operation is performed.  The condition has an info structure that
allows a handler of the condition to either abort the operation or
complete it by setting values in the structure and restarting the
condition signal.  When the condition is restarted, the signal_io_ I/O
module returns control to the caller of iox_ and returns the output
data in the structure as corresponding parameters of the iox_ call.

Applications using this I/O module must have a handler on the stack at
all times to handle the signal_io_ condition.


Attach description:
   signal_io_


Open operation:
All opening modes are supported.

I/O OPERATIONS (get_chars, get_line, put_chars, read_record,
rewrite_record, delete_record, read_length, position, seek_key,
read_key, write_record, control, modes)

All operations are supported in appropriate opening modes.  See NOTES
for a discussion of handing the condition associated with these
operations.


Notes:  When this module is called through iox_ to perform an I/O
operation as listed above, it signals the "signal_io_" condition with
an info structure given here.  The condition is restartable.

Applications using this module must establish a handler for the
condition that calls find_condition_info_ to locate the info structure.
If the condition is not handled, the default_error_handler_ will print
a default error message, unless the condition is associated with
user_i/o, user_output, user_input or error_output.  For these I/O
switches, terminates the process.

The returned_error_code in signal_io_info is initially set to
error_table_$action_not_performed, so if the condition is restarted
without first having the structure filled in, the iox_ call will return
error_table_$action_not_performed.


This condition does NOT pass through the condition walls established
when for new command levels.  If the application is attaching, for
example, user_i/o via this module, it must establish a command level
intermediary procedure (via cu_$set_cl_intermediary) that establishes a
new handler for the signal_io_ condition before calling the standard
intermediary (located via cu_$get_cl_intermediary).



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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
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    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