lesson
Find the first difference
1 · Learn
A bug is a problem in a program. To debug, compare what happened with what you intended. Trace one instruction at a time and find where they first differ.
Change a relevant part, then retest from the same starting state. If you also move the starting point, you may hide rather than fix the problem.
2 · Worked example
Goal: bell, pause, drum. Actual program: bell, drum, pause. I move the pause between the sounds and test again from the start.
3 · Your turn
A robot should move two squares, but its program says forward, forward, forward. What change should you test?
Check your answer
Remove the extra forward command, then run again from the same starting square and direction.
4 · Apply your learning
Ask a partner to trace your sound or movement program without running it. Compare their prediction with the actual result and explain any difference.
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