DEBUGGER

  DECTPU provides a debugger called TPU$DEBUG , stored in
  SYS$SHARE:TPU$DEBUG.TPU, or you can use a debug file of your own.

  To invoke DECTPU with the debugger, use /DEBUG and optionally specify the
  debug file you want to use.  DECTPU then executes the file containing the
  debugger before executing either TPU$INIT_PROCEDURE or the file specified
  with the /COMMAND qualifier.  For more information, see DCL HELP on
  EDIT/TPU/DEBUG.

  When you use TPU$DEBUG.TPU, DECTPU places the debugger window on the
  screen.  To set a breakpoint in the file you are debugging, press DO and
  issue debugger command SET BREAKPOINT followed by the name of the
  procedure where the breakpoint is to be set.  For example, if you wanted
  to set a breakpoint at the procedure FUM, you would issue the following
  command:

     SET BREAKPOINT fum

  After setting a breakpoint, use the command GO to switch control of
  execution from the debugger program to DECTPU.  You also use the GO
  command to look at the code you are debugging before setting breakpoints.

  The screen displays the file you specified on the DCL command line, and
  EVE commands are available.  To return to the debugger so you can set
  breakpoints, use the command DEBUG at the EVE command line.

  To compile all code in the buffer, use the EVE command EXTEND ALL.  To
  execute a procedure after compilation, use the EVE command TPU.

  When DECTPU encounters the first breakpoint in the session, the code you
  are debugging has not yet been placed in the debugger's source buffer.
  The debugger prompts for the name of the file containing your code.  Using
  your response, the debugger places your code in its source buffer.

  Once you have set breakpoints, compiled code, and started execution, you
  can use following commands for debugging:

  ATTACH [process]

     Suspends the current editing session and transfers control to another
     active process or subprocess.  (See EVE help on ATTACH.)

  CANCEL BREAKPOINT procedure-name

     Cancels a breakpoint set with the SET BREAKPOINT command.

  DEPOSIT variable := expression

     Lets you set the value of global variables, local variables, and formal
     parameters.

  DISPLAY SOURCE

     Clears text from the screen after use of the HELP or SHOW BREAKPOINTS
     command.  Causes the source display area to display your code.  By
     default, TPU$DEBUG.TPU defines CTRL/Z as DISPLAY SOURCE.

  EXAMINE variable

     Displays the current contents of global and local variables, global
     constants, formal parameters of the procedure that has been
     interrupted, and variables local to that procedure.  Local constants
     cannot be examined.

  GO

     Causes the debugger to relinquish control of execution until it is
     invoked again by a breakpoint, by the DEBUG command, or by the DEBUGON
     procedure.

  HELP

     Lists available debugger command and keypad bindings.

  QUIT

     Quits the debugger.

  SCROLL [-] number-of-lines

     Scrolls text in the source display area by the specified number of
     lines.  To scroll back through the code in the display area, use a
     negative value.  a negative number of lines.  To scroll forward by one
     line less than the number of lines in the display window, press NEXT
     SCREEN or GOLD/DOWN arrow.  To scroll back in the same way, press PREV
     SCREEN or GOLD/UP arrow.

  SET BREAKPOINT procedure-name

     Invokes the debugger when the specified procedure is executed.

     SET WINDOW top-line-number, length

     Puts the top of the debugger window at the line number specified and
     extends the window down by the second number specified.  The default
     length is 7 lines.  The minimum length is 3 lines.  The SET WINDOW
     command only changes the size of the source display area.  The output
     area and command line always occupy exactly one line.

  SHIFT [-] number-of-columns

     Moves the source display window left or right across the source code to
     display text wider than the screen.  To move left, press GOLD/LEFT
     arrow, then enter the number of columns to move.  To move right, press
     GOLD/RIGHT arrow, then enter the number of columns to move.

  SHOW BREAKPOINTS

     Lists the current breakpoints in the debugger source window.  To
     re-display code in the source window, use the DISPLAY SOURCE command.

  SPAWN [command-string]

     Suspends the current editing session and creates a subprocess.  (See
     EVE help on SPAWN.)

  STEP

     Executes one line of DECTPU code, then returns control to the debugger.
     If you have several DECTPU statements on one line, all statements are
     executed before control returns to the debugger.

  TPU statement

     Executes the DECTPU statement you specify.  (See help on TPU.)

  Related Topics

     DEBUG_LINE   SET(DEBUG)