Futurebasic/Language/Reference/on lprint

Description
This statement designates a particular function or subroutine as an idler routine to be called by the printer driver during printing. The actual number of times that this function is called depends on the driver and the hardware.

You may use the  vector to rotate through a series of cursors, check for a Command-Period key press, or update the status of a print job.

Note: If you use the syntax, then  must refer to a function which was defined or prototyped at an earlier location in the source code.