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TOPS-20 Beware File
COPYRIGHT (C) 1976,1977,1978,1979,1980 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
This document supplements the TOPS-20 manuals by pointing
out hints and potential problems discovered at the last
2.0 TOPS-20 MONITOR AND UTILITIES
2.1 File and Directory Limitations
Due to the increased size of the file descriptor blocks
(FDBs) in Release 4, the following numbers will be somewhat
smaller than their Release 3A values:
1. The number of files in a directory
2. The number of subdirectories within a directory
3. The number of top-level directories in the system
2.2 Programs Running Under SYSJOB
The batch commands in PTYCON.ATO have been replaced by
commands in SYSJOB.RUN and SYSTEM.CMD. The programs are
invoked by commands in SYSJOB.RUN, and the commands to the
programs are in SYSTEM.CMD, which is read by OPR. The
defaults are 3 batch streams, 2 line printers, and 1 card
reader. If you wish to remove 1 line printer, delete one of
the "RUN SYS:LPTSPL" lines in SYSJOB.RUN, and change
SYSTEM.CMD to read "START PRINTER 0". To remove the card
reader, delete from SYSJOB.RUN "RUN SYS:SPRINT" and "RUN
SYS:CDRIVE", and delete the line in SYSTEM.CMD "START READER
2.3 EXEC Commands
The ^ESET STRUCTURE commands have been replaced by OPR
commands. (OPR runs under PTYCON.)
The SREMOVE command is replaced by the DISMOUNT STRUCTURE
name:/REMOVE command. The TMOUNT, SMOUNT, and SDISMOUNT
commands are in Release 4 for compatibility only. They have
been replaced by MOUNT TAPE, MOUNT STRUCTURE, and DISMOUNT
STRUCTURE, respectively, and will be removed in the next
release. The TMOUNT and SMOUNT commands will behave a
little differently under Release 4. The TMOUNT command will
work only if the ENABLE TAPE-DRIVE-ALLOCATION command is
included in the 4-CONFIG.CMD file.
2.4 2020 Card Reader
There is a problem in the processing of the hopper-empty
condition by card readers on 2020 systems. The data on the
last card in the hopper is not processed. This can be
circumvented with the following technique:
For each hopperful of data, append a blank card to the cards
in the hopper. This will cause the data on the former last
card to be processed. The blank card will be passed by the
reader, but its contents ignored. Note that this applies to
every physical hopperful of cards, not to logical "decks".
User-mode DDT (UDDT) now occupies pages 766 through 777 of
the user address space. Programs that rely upon using pages
766 and 767 may possibly not operate correctly if DDT is
merged with them.
2.6 PTY Handling
Prior to Release 4, if a program did a BOUT or a SOUT to a
PTY and the PTY's input buffer was full, one or more
characters would be lost and a bell would be echoed in the
output stream. In Release 4, a program trying to output to
a PTY with a full input buffer will receive an illegal
instruction trap with error code IOX33. The controlling job
can handle the error condition by employing an ERJMP or
ERCAL following the BOUT or SOUT.
2.7 Split-speed Terminal Lines
Terminals that send XOFF and XON characters automatically to
prevent the system from overflowing their internal buffers
(VT100 for example) may encounter difficulty if the input
baud rate is set slower than the output baud rate. This is
because the terminal will not be able to send the XOFF
character quickly enough to stop the system from
2.8 Execute-only Programs
Files that are protected as execute-only cannot be accessed
under 3A. Therefore, if you do drop back to 3A, be sure to
reprotect any files that were set to be execute-only under
More information is provided in chapter 2 of the release 4
TOPS20 Monitor Calls Reference Manual.
2.9 DFIN and DFOUT
The DFIN and DFOUT monitor calls now use the normal KL10
double-precision floating point format numbers as described
in the System Reference Manual. The KA10 double precision
format mentioned in the Monitor Calls Manual is no longer
2.10 The PLEASE Command
The only supported mechanism for invoking the PLEASE program
is via the PLEASE command. In particular R PLEASE or GET
SYS:PLEASE are not valid and the PLEASE program may not
operate correctly if invoked in these ways.
If the POLICY-PROGRAM clause is used in the ENABLE
CLASS-SCHEDULING command in the 4-CONFIG.CMD file, SETSPD
will not process it correctly. If only the word POLICY is
used, the intended result will occur.
Please refer to the file DECNET.BWR on the DECNET tape for
"beware" information regarding DECNET.
4.0 BUILDING PROGRAMS FROM SOURCES
4.1 Building the TOPS-20 Monitor
The TOPS-20 monitor must be built using the MACRO and LINK
that are distributed with Release 4. Note that in Release
4, no PSECT overlaps are permitted when building the
4.2 Building RUNOFF
Building RUNOFF generates a copy of SCNMAC.UNV that is not
the correct version for building other software. To avoid
any problems, build RUNOFF in a separate directory.
5.1 Hardware Field Change Order (FCO)
Because of extensive changes to the terminal handling code
in Release 4 of TOPS-20, FCO 20FE-R-0001 must be installed
in all 2040, 2050, and 2060 processors before running
Release 4. This is a required FCO, released February, 1979.
The FCO places a DB11-A bus repeater in the first system
unit slot of the expansion box in the front end. Please
check and be sure that the FCO is installed and a DB11-A is
already in the first system unit.
If you require this FCO, contact your Regional FCO
Coordinator immediately (EQ-00920-00).
PLEASE NOTE: TOPS-20 WILL NOT RUN ON A 2040, 2050, OR 2060
PROCESSOR WITHOUT THIS FIELD CHANGE ORDER.
5.2 Front-End Versions
It is recommended that Release 3A of RSX-20F be used with
Release 3A of TOPS-20, and that Release 4 of RSX-20F be used
with Release 4 of TOPS-20.
The data record output feature of WATCH is not supported in
the version of WATCH being released with TOPS20 Release 4.
Note that the record formats are reflected in the new WATCH
document in the Software Notebooks. The documentation is to
be used for information only until such time as the version
of WATCH that supports this feature is released.
6.2 USAGE File Specification
The controller field in the tape mount record is defined to
be 2 characters. It is actually 3 characters, which means
all fields after the controller field should be shifted by
one. The total length of the record is 149 characters.