





                  FORTRAN SYMBOLIC DEBUGGING TOOL (SDT) 


     SDT is different from most FORTRAN symbolic debugging tools  currently
available for the PDP-11 for the following reasons:

     1.  It steps through a program by FORTRAN statements and  can  display
         each statement at the time it is executed.

     2.  It supports a "split screen" format for CRT  terminals.   SDT  I/O
         will be above the dashed line and regular program I/O below it.

     3.  It maintains breakpoint traps in the overlay loading mechanism (if
         used)  and  will set traps, as required, as different overlays are
         loaded.

     4.  It  consists  of  two  basic   modules   which   communicate   via
         send/receive directives:  

         1.  A small module, 'LIMPIT', approximately 1KW in length, that is
             part of the user task being debugged.

         2.  The separate program, DEBUG, that gets  requested  by  LIMPIT.
             DEBUG performs all table generation, file I/O, command parsing
             and communications with the terminal.

         This allows SDT to handle large tasks  that  are  near  their  32K
         address limit.


     SDT was written for IAS, but should  be  fairly  easily  modified  for
RSX-11M  or  M+.   It  has  the option of using CRT screen formatting.  The
original code is for Beehive terminals, but all of the  cursor  positioning
code is in the module POSITN.MAC and is well commented.

     When Task-building DEBUG, several warning  errors  (4  of  them)  will
occur.   Ignore  them  - they are due to the same module being in different
overlays.

     If you have any comments, bug fixes, enhancements or whatever,  please
let me know.....



                    Scott Leatham
                    The Boeing Company
                    Seattle, Washington
                    (206) 237-6363

