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POP command

The POP command terminates the current level of  TOPS-20  and  returns
you to its superior process.


Format

     @POP (COMMAND LEVEL)


Characteristics

     POP the Opposite of PUSH

          You can do one and only one POP command for  every  previous
          PUSH  command.   Giving  too many POP commands will cause an
          error message to be printed on your terminal.

     Job Parameters Affected by POP

          As soon as you complete a valid POP command at some level of
          TOPS-20,  you  give  up the copy of memory for that level of
          TOPS-20 and any program  you  were  running.   Any  defaults
          established  at  that  level  (such as default filespecs for
          LOAD-class and EDIT-class commands,  defaults  specified  by
          SET DEFAULT commands) are cancelled as well.  If POP returns
          you to a higher  level  of  TOPS-20,  all  these  parameters
          revert to any values established at that higher level.


Special Cases

     Returning to Other Programs With POP

          The POP command usually returns you to the level of  TOPS-20
          from  which  you  gave  a  previous PUSH command.  But a few
          system programs such as PTYCON and OPR, also  allow  you  to
          give  PUSH  to  get  a new level of TOPS-20.  Giving the POP
          command to  this  level  of  TOPS-20  returns  you  to  that
          program.


Effect on Memory and Terminal

     The POP command clears memory, terminates the  current  level  of
     TOPS-20 and returns your terminal to the previous TOPS-20 command
     level (but see Special Cases, above).  Memory  for  the  previous
     TOPS-20 command level is not affected by this action.


Related Commands

     CONTINUE              for resuming  execution  of  a  program  in
                           memory

     INFORMATION SUPERIORS for information on the number of forks that
                           are superior to the current EXEC level

     PUSH                  for obtaining a new level of TOPS-20


Examples

     1.  Give the POP command to return  to  a  higher  level  of  the
         TOPS-20 command processor (EXEC).

         @POP

     2.  Run a program and halt it with CTRL/Cs.  Give a CONTINUE STAY
         command  to  resume  its execution, and then the PUSH command
         for a new level of TOPS-20.   Run  another  program  at  this
         lower  level, then use the POP command to return to the first
         level; in this case you return  before  receiving  the  final
         message of the first program.

         @RUN DMN

         ^C
         @CONTINUE /STAY
         @PUSH

          TOPS-20 Command processor 7(7)
         @RUN TESTF1

         THIS IS A TEST.

         CPU time: 0.03  Elapsed time: 0:72
         EXIT
         @POP
         EXIT