02/18/85  mtape_set_defaults

Syntax as a command:  mtape_set_defaults OPN -control_args


Function: sets default arguments used by the mtape_ I/O module.


Arguments:
OPN
   is the type of tape operation (attach, open, close, or detach) that
   uses the default arguments.


Control arguments:
-arguments ARGS, -argument, -ag ARGS
   are the arguments appropriate to the specified operation and tape
   format.  They must be syntactically correct and appropriate to the
   conditions under which they are applied.  You must supply
   -arguments, which must be the last one specified on the command
   line.
-pathname path, -pn path
   is the name of the value segment in which the requested default
   values are stored.  If you omit it, the value segment >udd>[user
   project]>[user name]>[user name].value is used.


-volume_type VT, -vt VT
   specifies the volume type (ansi or ibm) used by mtape_ to select the
   per-format module for tape processing.  Give -volume_type when you
   specify either the open or close operations; omit it when you supply
   either the attach or detach operations.  This control argument,
   along with -operation, defines restrictions on the specification of
   the default arguments (see the mtape_ I/O module in the Subroutines
   manual).


Notes: The command sets the default arguments associated with a given
volume type and tape processing operation.  These default arguments are
eventually used to complete attach, open, close, and detach
descriptions when you have not explicitly supplied all the necessary
information.

The default arguments specified in the command line are processed by
the mtape_ argument processing subroutine to assure that they follow
all the restrictions imposed by their intended future usage.  The
result of this processing is then converted to a character string and
is stored in the data space of a specified value segment.  The stored
value is later located and used as default information for argument
processing when tapes are being processed by the mtape_ I/O module (see
the Programmer's Reference Manual for tape processing).


Notes on using default arguments: When it is necessary to use default
arguments in a particular application, they are located by the mtape_
argument processing routine using the mtape_arguments search list.  The
default mtape_arguments (mtape_args) search list, is as follows:
   mtape_arguments
   mtape_args
      >udd>[user project]>[user name]>[user name].value
      >site>mtape_arguments.value
      >sss>mtape_arguments.value

You can add or delete search paths as necessary using the search paths
commands.


In locating default arguments, the mtape_ argument processing routine
looks in every value segment in the search list and takes the
appropriate default arguments from each (if it finds them).  Whether a
group of default arguments is determined to be appropriate for an
application depends on the volume type and tape processing operation
for which is intended.

Default arguments from value segments at the top of the search list
take precedence over those from value segments at the bottom.
Equivalently arguments on the right side of an argument list take
precedence over arguments on the left.  This means that after all
default arguments for a particular application have been gathered from
the search list, if an argument occurs more than once, the argument
with the highest precedence is retained and the others are excluded.
The result is called the default linear form.


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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