Trailing-Edge
-
PDP-10 Archives
-
BB-PBQUC-BM_1990
-
help/ddt.hlp
There are 6 other files named ddt.hlp in the archive. Click here to see a list.
DDT command
The DDT command loads or merges a debugging program into memory
(unless one is already there), then starts it.
Format
@DDT/switch(es)
where:
/switch is one or more of the following:
/OVERLAY allows pages of the DDT program to
be loaded over pages occupied by
the existing program in memory
/USE-SECTION:n
specifies the memory section (from
0 to 37 octal) into which the
debugging program is to be loaded,
run, or merged
Characteristics
If a Debugging Program is Already Loaded
If you have already loaded a debugging program into memory
along with your program, the DDT command starts the
debugging program.
If Your Program, But Not a Debugging Program, is Already Loaded
If a program containing symbols is in memory without a
debugging program, the DDT command merges SYS:XDDT.EXE into
memory, then starts this debugging program. However, if
some of XDDT's pages include some of the same pages as the
existing program in memory, then the DDT program is not
placed into memory, and you receive the error message,
"?Illegal to overlay existing pages." To force the pages to
be overlaid, reissue the DDT command using the /OVERLAY
switch.
If There is No Current Program
If you do not have a program in memory, or if no program in
memory is in the current fork, or if your program does not
contain symbols, the DDT command puts SYS:XDDT.EXE into
memory and starts it.
Compatibility with Previous DDT Versions
The UDDT program run by the DDT command has been replaced by
the XDDT program. For compatibility with programs that
reference UDDT, a stub program named UDDT references the
XDDT program.
Hints
Using DDT to Create a Program
You can use DDT to begin typing instructions directly into
memory, without first putting the instructions into a file
for later compilation and loading. Give a RESET . (period)
command to clear the current fork, then the DDT command.
This will load the SYS:XDDT.EXE program. Then you can give
commands within XDDT to create your own program. When using
the XDDT program, you can use all the symbols in the system
parameter file MONSYM.MAC.
See the TOPS-20 Monitor Calls Reference Manual for more
information about MONSYM.MAC. This method of writing a
program is most useful for testing special cases, or for
learning to use TOPS-20 monitor calls.
Special Cases
Using COBDDT
If you put COBDDT into memory along with a COBOL program,
the DDT command starts the UDDT program, not COBDDT. Use
the REENTER command to start COBDDT in this case.
Effect on Memory and Terminal
The DDT command merges the SYS:UDDT.EXE program into the current
fork and starts it, or loads and starts SYS:XDDT.EXE. If you
have already loaded a debugging program, the DDT command starts
this program.
Related Commands
DEBUG for loading your program along with a
particular debugging program (such as
FORDDT or COBDDT).
FORK for selecting the current fork.
INFORMATION MEMORY-USAGE
for displaying the numbers of pages
occupied by the program in memory.
Examples
1. Give the DDT command to begin debugging a program in the
current fork in memory.
@DDT
DDT
2. Give the DEBUG command to debug a FORTRAN program; type a
CTRL/C to return to TOPS-20 command level so you can find out
the current load averages and number of jobs for the system.
Return to your debugging program (FORDDT in this case) by
giving the DDT command.
@DEBUG TESTF1
LINK: Loading
[LNKDEB FORDDT Execution]
STARTING FORTRAN DDT
>> ^C
@SYSTAT SYSTEM
Fri 20-Apr-79 13:50:01 Up 36:47:55
35+14 Jobs Load av (class 0) 0.72 0.81 1.33
@DDT
STARTING FORTRAN DDT
>> START
THIS IS A TEST.
END OF EXECUTION
CPU TIME: 0.04 ELAPSED TIME: 0.33
EXIT
@INFORMATION MEMORY-USAGE
66. pages, Entry vector loc 0 len 254000
0-12 Private R, W, E
400 Private R, W, E
401-466 <SUBSYS>FOROTS.EXE.3 3-70 R, CW, E
3. Display the programs in memory with the INFORMATION
FORK-STATUS command. Then use the FORK command to make
the CLIP program the new current fork. Verify this with
INFORMATION FORK-STATUS and then merge the UDDT program
with the CLIP program.
@INFORMATION FORK-STATUS
EMACS (1): Kept, HALT at 50340, 0:00:03.6
CLIP (2): Kept, HALT at 70363, 0:00:00.2
=> UNITS (3): HALT at 162, 0:00:00.9
@FORK CLIP
@INFORMATION FORK-STATUS
EMACS (1): Kept, HALT at 50340, 0:00:03.6
=> CLIP (2): Kept, HALT at 70363, 0:00:00.2
UNITS (3): HALT at 162, 0:00:00.9
@DDT
DDT