How do I terminate the execution of .gra files

You have are several options:

The end statement returns control to the caller. It can be the command line or another .gra file. The end statement has an optional parameter which is used to signal the completion status of the .gra file. The status is tested with a call to gra_status().
```
if something_is_wrong 
  end 0 
endif
...
end 1
```
The command set abort on terminates the execution of .gra files and returns to the command line.
A keystroke, like pressing the space bar, may can be used to initiate a normal end:
```
  inquire/key s1
  if search_symbol( s1)
    if !(s1 - 32)
      end
    endif
  endif
```
Notice that inquire/key does not wait for a keystroke, it just reads the input buffer. The number 32 selects the space bar.
Pressing Ctrl-C returns control to the command line. It is not recommended to use Ctrl-C because data structures that were allocated during the startup of the .gra file are not freed.