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START command

The START command begins execution of the program in the current fork.


     @START (PROGRAM) location/switch


     location       is the octal or symbolic address  where  you  want
                    the program to start.
                    Default location - the  normal  starting  address,
                                       that  is, the first word in the
                                       program's entry vector

     switch         is  a  keyword,  chosen  from  the   list   below,
                    indicating your choice of START command options.

                        START Command Switches

/BACKGROUND    keeps your terminal at TOPS-20 command level and starts
               execution  of the program in a "background" fork.  When
               the program attempts to do terminal input or output, it
               halts  and  displays  the  message [FORK-NAME wants the

/NORMALLY      restores your terminal to command level (if any) within
               the program

/STAY          keeps your terminal at TOPS-20 command  level.   Output
               from  the  program  is  sent  to  the  terminal  and is
               intermixed with whatever output is currently displayed.
               When the program attempts to read from the terminal, it
               can randomly intercept input intended for the  EXEC  or
               another  program.   Therefore,  use  this  switch  with
               programs that, once started,  do  not  request  further
               terminal input.


     Starting a Noncurrent Fork

          When you START a noncurrent  fork,  the  fork  becomes  your
          current fork.


     Further Information

          The START command is one of the  TOPS-20  multiforking-class
          commands.   For more information about multiforking, see the
          section named  Running  Multiple  Programs  in  the  TOPS-20
          User's Guide.

          For more information about entry vectors,  see  the  TOPS-20
          Monitor Calls Reference Manual.

Special Cases

     Running COBOL Programs a Second Time

          After running a program (with a RUN or EXECUTE  command,  or
          with  a GET and START or LOAD and START combination) you can
          usually run it again using START.   COBOL  programs  are  an
          exception:  to run them again you must reload them.


     Programs Competing for Terminal Input

          If you use START /STAY to run  a  program  in  a  background
          fork,  either  at  the  current  or  at a lower EXEC command
          level, (see Hints - Using PUSH to Get a New TOPS-20  Command
          Level,  above),  the  program  can  request  input  from the
          terminal while you are giving input to the EXEC  or  another
          program.   This  input  can  be  randomly intercepted by the
          background program when it requests terminal input.  Usually
          though, the EXEC or the current program receives the input.

          When  terminal  input  is  intercepted  by  the   background
          program, the program usually types input error messages.  To
          give input to the program, stop the program  by  typing  two
          CTRL/Cs  or  the  program's  exit  command.   Then,  if  the
          background program is at a higher EXEC command  level,  give
          POP  commands  to  return  to  the EXEC level that holds the
          background program.  (POP terminates the  current  EXEC  and
          erases  programs in its memory.)  Finally, give the CONTINUE
          /NORMALLY command; this puts you at program command level so
          that you can give the requested input.

          Input is intercepted by  the  background  program  randomly.
          Therefore,  you may have to type extra CTRL/Cs, program exit
          commands, and POPs.  To reduce confusion about the direction
          of  terminal  input,  it  is  recommended that you use START
          /STAY only when you plan to work at the current  EXEC  level
          while  a  program  runs  in  a  background  fork.  Use START
          /BACKGROUND when you plan to work at a lower EXEC  level  or
          at another program command level.

          When  a  program  started  with  START  BACKGROUND  requests
          terminal  input,  it sends the message, [FORK-NAME wants the
          TTY].  No input is taken by the background program until you
          return to program command level with CONTINUE /NORMALLY.

     No I/O Control with Some Programs

          Most programs read and write data to  the  terminal  through
          standard   input  and  output  designators.   Some  programs
          however, use different methods  of  communicating  with  the
          terminal.   Therefore, when you use /BACKGROUND and /STAY to
          control terminal input and output from  a  background  fork,
          the  input  and output behavior of programs with nonstandard
          designators can be unpredictable.

     Execute-only Programs

          Programs that are execute-only can only be started at  their
          normal starting address.

Related Commands

     CONTINUE                 for  resuming  execution  of  a   halted
                              program in memory

     FORK                     for changing the current fork

     FREEZE                   for halting a program  in  a  background

     GET                      for  placing  executable   programs   in

     INFORMATION FORK-STATUS  for displaying the number and the status
                              of each fork in your job

     KEEP                     for giving a fork a kept status

     LOAD                     for loading source  or  object  programs
                              into memory

     REENTER                  for starting the program  in  memory  at
                              its alternate entry point (if any)

     SAVE                     for saving a loaded program in  an  .EXE

     ERUN, RESET,             other multiforking-class   commands  for
     SET NAME, SET PROGRAM,   performing related functions


     1.  Start the program currently in memory.


     2.  Put an executable program in memory and start it.   Then  run
         it again.

         @GET TESTF1.EXE

         THIS IS A TEST.

         CPU TIME: 0.04  ELAPSED TIME: 0.23

         THIS IS A TEST.

         CPU TIME: 0.02  ELAPSED TIME: 0.02

     3.  Begin using the FILCOM program to compare two files.  Give  a
         CTRL/C  to  halt  FILCOM,  then  a  CTRL/T  to  determine the
         location where it was stopped.  Give the DDT command, and  do
         some  work  within  the DDT program; leave DDT with a CTRL/Z,
         returning to TOPS-20 command level.  Give the  START  command
         to start FILCOM again, using as argument the address reported
         by CTRL/T above.


         ^T 14:49:03 FILCOM ^C from Running at 400543  Used 0:00:03.1 -
         in 0:04.39, Load 2.44 in 0:01:33

         3/   PAT..+361,,3066
         4/   56
         @START 400543

         No differences encountered

     4.  Place the CLOCK program (not DIGITAL  supported)  in  memory.
         KEEP  the CLOCK program so that it will remain in memory when
         you run other programs.  Then, start the CLOCK program in the
         background.   CLOCK  will  display  the  time every half hour
         while you run other programs and EXEC commands.

         @GET CLOCK.EXE
         [11:30 AM]