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COBOL.BWR -- Beware file for COBOL-74 version 12C
Nov 1985






























COPYRIGHT (C) 1985 BY
DIGITAL EQUIPMENT CORPORATION, MAYNARD, MASS.


THIS SOFTWARE IS FURNISHED UNDER A LICENSE AND MAY BE USED AND  COPIED
ONLY  IN  ACCORDANCE  WITH  THE  TERMS  OF  SUCH  LICENSE AND WITH THE
INCLUSION OF THE ABOVE COPYRIGHT NOTICE.  THIS SOFTWARE OR  ANY  OTHER
COPIES  THEREOF MAY NOT BE PROVIDED OR OTHERWISE MADE AVAILABLE TO ANY
OTHER PERSON.  NO TITLE TO AND OWNERSHIP OF  THE  SOFTWARE  IS  HEREBY
TRANSFERRED.

THE INFORMATION IN THIS SOFTWARE IS SUBJECT TO CHANGE  WITHOUT  NOTICE
AND  SHOULD  NOT  BE  CONSTRUED  AS  A COMMITMENT BY DIGITAL EQUIPMENT
CORPORATION.

DIGITAL ASSUMES NO RESPONSIBILITY FOR THE USE OR  RELIABILITY  OF  ITS
SOFTWARE ON EQUIPMENT WHICH IS NOT SUPPLIED BY DIGITAL.

COBOL.BWR -- Beware file for COBOL-74 version 12C               Page 2


1.  Differences between 12B and 12C

COBOL-74 has been changed to conform to the standard so that if a file
is  opened  for  I/O  the  file  must already exist.  The file will no
longer be created.

The default for WRITE without any advancing information  is  different
between COBOL-68 and COBOL-74.  This is not a change, but the COBOL-74
documentation has been changed to correctly state that the default  is
AFTER ADVANCING 1 LINE.

2.  Extra carriage-return problem

To comply with Federal regulations for a FIPS certified  compiler  the
following  "feature"  had to be provided.  In general, if a record was
written with WRITE AFTER ADVANCING and the  next  record  was  written
with WRITE BEFORE ADVANCING, then the first record must be overprinted
by the next record.  In particular, if the last record in  file-1  was
written  with WRITE AFTER ADVANCING and the first record in file-2 was
written with WRITE BEFORE ADVANCING and file-2 was output to the  same
device  (e.g.   a LPT:) immediately after file-1, then the last record
of file-1 must be overprinted by the first record of file-2.  The FCTC
has a test which does just that.

Clearly we need an extra carriage-return between the two records.  The
two choices were, put it at the front of the BEFORE ADVANCING file, or
at the end of the AFTER ADVANCING file.  We chose the latter since  we
believe  it  is the less common case (even though it is the default in
COBOL-74) and an extra carriage-return will do less harm at the end of
a file.

If, for some reason, you do not wish this "feature" then you can  edit
CBLIO.MAC  to  remove  it.   At  location  NOXCR.  replace the current
instruction by a JFCL.  Note that we cannot support this change as  it
violates the Federal standard.

3.  COBOL-74 old REL files

At the REL file level if anyone keeps COBOL REL files except in a LINK
library  file),  the  only  problem  is with COBOL-74 and COBDDT.  The
compiler output of Debug paragraph names was changed to  be  identical
with COBOL-68.  This means that COBDDT V12C would display an incorrect
paragraph name for a COBOL-74 paragraph compiled with  COBOL-74  V12A.
We  do not think that this is a problem since people tend to recompile
before debugging, and working library files  should  not  need  to  be
debugged again.  In any case all that has to be done is to recompile.

4.  COBOL 12A and COBDDT 12C incompatibility

Except for the above-mentioned problem,  all  programs  compiled  with
version 12A of COBOL can be debugged with COBDDT 12C with no problems.
However, COBDDT 12C supports qualification of variables by  specifying
the  filename  (e.g.   "DISPLAY  A  IN FILE-1").  This is a feature of
COBDDT 12C which was not supported by COBDDT 12A, and compiler support
needed  to  be  implemented.   Thus you cannot use this new feature of

COBOL.BWR -- Beware file for COBOL-74 version 12C               Page 3


COBDDT 12C until you recompile the program module using COBOL 12C.

COBOL.BWR -- Beware file for COBOL-74 version 12C               Page 4


5.  SIMULTANEOUS UPDATE:

There is currently an incompatibility between TOPS-10 and TOPS-20 that
causes a problem for simultaneous update under TOPS-20.  Under TOPS-10
it is possible to have one  program  open  a  file  for  INPUT  (only)
without  simultaneous  update  control  while at the same time another
program is running that opens the same file for  simultaneous  update.
Currently  TOPS-20 does not support the open mode that allows this, so
that the first program to open the file will stop the other, with  its
different  mode,  from running (it will die with an open error).  This
incompatibility will be fixed in TOPS-20  Release  5.   The  necessary
changes  have  been  made  to  version  12C,  however they are under a
feature test switch TOPS2X which is currently turned off as  the  code
has  not  yet  been  extensively  tested.  It is not possible to patch
Release 4 so version 12C will ship with TOPS2X turned  off.   At  some
time  after Release 5 has shipped and the code in CBLIO tested we will
inform the customers of the pros and cons of turning on TOPS2X.


6.  SIMULTANEOUS UPDATE:

Because of a problem in the TOPS-20 monitor, records updated in a file
via  SMU mode which cause the length of the file to be extended by one
program will not be found by other users until both programs close and
reopen  the  file.   To  overcome this restriction for ISAM files, the
ISAM utility sets the file size for .IDX and .IDA files  to  +infinity
(2**35  -1)  in the file descriptor block (FDB).  Please note that the
files physical length is the correct number  of  bytes  written.   The
file's size in pages is displayed correctly by VDIRECTORY.

This fix allows  simultaneous  update  users  to  process  ISAM  files
correctly.   However  some programs or TOPS20 commands (such as FILCOM
or QUEUE LPT:  = FILE/PRINT:OCTAL) which attempt to  access  the  file
sequentially will run improperly - they will run and run and run...

A special purpose utility SETEOF.EXE is included in  the  BINARY  save
set.   SETEOF  may  be  used  to  extend the file size in the FDB to a
large, user specified size or to reduce a file with an  extended  file
size  to the actual file size (rounded upward to the next page).  This
will allow users of random files in simultaneous update mode to extend
the  file  size  before  processing.   Conversely, if a user wishes to
sequentially process a file with an extended file size, the  user  may
use  SETEOF  and  specify a file size of "0" to reduce the file to the
actual file size (rounded upward to the next page).

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