You can attempt to interrupt Ghostscript from whatever it is doing with the <command><period> key sequence (it is also available as 'Interrupt' in the 'Ghostscript' menu). Interrupting a PostScript program is inherently unpredictable. This is because a PostScript file can trap the user-interrupt and refuse to stop! Interrupt is implemented so that it should work smoothly in most cases, but you can't be sure. If it doesn't work, hit it a few more times.
Similarly, Quit is also something that a PostScript program can refuse to do! Sometimes, Ghostscript may not appear not to quit. Always give it a few seconds to try. If it just won't quit, the work around is to type: <option><command><escape> (all at once) to invoke the System 7 Forced Quit dialog.
