Their size, shape, location, icon size, icon shape, icon location, font size, color, and title identification are all specified as options in these two commands. They are also set up as scrollable windows, each with 200 lines of scroll buffer. This tells the shell to run the commands in the background, which is necessary if all of them are to run and return control to the telnet session's login shell when the script is done executing. The xterm processes can become orphaned if MacX crashes or terminates without killing them. Orphaned processes can tie up mainframe system resources, which can be released only by manually killing the offending processes.
Good citizenship demands that such housekeeping be attended to regularly.
Changing Fonts To change the fonts used in a Xterm window in general or an Emacs window in particular, you need to press the control key and the right mouse button in the xterm or Emacs window. The former affects all MacX windows opened subsequently, while the latter affects only the currently active MacX window.