13. The method of claim 1 wherein the computer system includes a user-operated editor for editing the first corresponding instructions of the source program in the ladder-based language.
13. The method of claim 1 wherein the computer system includes a user-operated editor for editing the first corresponding instructions of the source program in the ladder-based language. 14. The method of claim 13 further comprising the step of converting the first corresponding instructions of the source program in the ladder-based language, as edited, to third corresponding instructions in the high-level text-based language automatically after source program is edited.