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Chapter 1: BASIC’s Basics
errors such as division by zero, or references to a non-existent file, forenample. When a mn- time error is discovered, the program halts andax Alertis displayed with a brief indication of what theproblem is. As with syntax errors, the cursor will position itself near the offending statemenlin theEdit window. Forexample, seethe picture on the following page.

Whenaprogram stops because of a run-time error, you can besure thatexecution has atleast started, and so in tracking down she bug it may be helpful if to inspect the program’s variables. (You can do this by entering PRINT variable-name into the Dialogue window.) Changing theprogram willmean losingthecontentsoflhesevariables,and youmay notwish to do this; so before you can edit your program after a mo-time bug, a dialogue appears warning you that you are abeulto destroy the value held in your pmgram’s variables.

If you need to pre-ocan a program without mnning it, select the option Check out on the Program menu.

If the program runs succesufully, it will finiub by displaying an Alert with the words Program END. Clearthe dialogue by clicking on OK.
BASIC 2 PIus: User Guide & Quick Reference 5

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