Practice Debugging in CS Thinking
Use these practice problems to test your method after reviewing the concept explanation and worked examples.
Quick Recap
The systematic process of finding, diagnosing, and correcting errors (bugs) in a program.
Detective work—observe the wrong output, form a hypothesis, test it, then fix what's wrong.
Example 1
mediumThis code should print numbers 1 to 5 but has a bug: SET i = 1. WHILE i < 5: OUTPUT i. i = i + 1. Find and fix the bug.
Example 2
mediumThis code calculates an average but gives the wrong answer: SET total = 0. FOR each num in [10, 20, 30]: total = total + num. SET average = total / 2. OUTPUT average. The input has 3 numbers. Find the bug.
Example 3
mediumThis code should output the largest number in [3, 7, 2, 9, 4] but outputs 3: SET largest = nums[0]. FOR i = 0 TO LENGTH(nums)-1: IF nums[i] > largest THEN largest = nums[i]. OUTPUT largest. Trace and verify if it is correct, or find the bug.
Example 4
mediumA program to sum the numbers 1 through 5 uses `SET total = 1; FOR i = 1 TO 5: total = total + i`. It outputs 16 instead of 15. Identify the bug and fix it.