POPO and PUSHO provide the interface to the option stack. PUSHO will push the current set of options on the option stack. POPO can then later be used to restore them. Useful if you want to change some options in an include file and you don't want to destroy the options set by the program that included your file. The stacks number of entries is limited only by the amount of memory in your machine.
Last updated 20 July 1997 by Carsten Sorensen