This button opens a dialog box prompting you for a run command. The command in the dialog when it opens is:
pure_run a.out arg1 arg2 . . .
where "a.out arg1 arg2 . . ." is the full command line last used to execute the program, or just the program name if it has never been run in this session. The script pure_run runs the command line in a suitable xterm or hpterm. You can modify the command, or press OK to run it as it is given.
You can further customize the run command by copying the pure_run script from the Purify installation directory and modifying it. Set $Path to point to the modified version.