On a forum at the museum of hp calculators, one of the HP engineers explained to me how programs are interpreted. Whenever you exit a program after editing, there is a compilation step that is done. Some optimization is done as the source code is converted to a form of P-code internally. Note that this is why comments do not affect speed, as these don't exist in the P-Code. I just thought you should be aware of this, as it's not really the source that you are looking at that is executed, but whatever it's converted into in the compilation step.