The UFL comes with a directory of simple routines to use the fonts in your own programs. These perform argument checking and can be used in User RPL programs or as the basis for System RPL programs. Included in this directory are the following:
Returns 0 or 1 on whether the UFL library exists.
Returns 0 or 1 depending on whether the FNT1 exists. Errors if the UFL does not exist, so check UFL? first.
Returns 0 or 1 depending on whether FNT2 exists. Errors if the UFL does not exist, so check UFL? first.
Takes a string on level 2 and a real number on level 1, then displays the string on the screen using FNT2. The real number should be a line number between 1 and 7, where 1 is the top of the screen and 7 is the bottom. Errors for insufficient or bad arguments, UFL does not exist, FNT2 does not exist, or if the specified level is not between 1 and 7.
To avoid bogging down the main access routines, each level of error checking assumes you have properly checked the previous level. For example, if the UFL does not exist and you try to use DISPN, you will find you get Error: Undefined XLIB Name rather than a nice error message.