While Loop CS Thinking Example 1

Follow the full solution, then compare it with the other examples linked below.

Example 1

medium

Trace: SET n = 1. WHILE n < 100: n = n * 2. OUTPUT n. How many iterations?

Solution

1
Step 1: Start at $n = 1$ and double each time: $1 \to 2 \to 4 \to 8 \to 16 \to 32 \to 64 \to 128$ .
2
Step 2: After reaching $128$ , the condition $128 < 100$ is false, so the loop stops.
3
Step 3: The loop doubled $n$ seven times, so the output is $128$ after $7$ iterations.

Answer

Output: 128. 7 iterations.

A WHILE loop repeats as long as its condition is true. The condition is checked before each iteration, so the loop may execute zero or more times.

About While Loop

A control structure that repeats a block of code as long as a specified condition remains true. The condition is checked before each iteration, and if it is false from the start, the loop body never executes at all.

Learn more about While Loop →

More While Loop Examples

Example 2 medium

Write a WHILE loop that asks the user for input until they type 'quit'.

Example 3 medium

Trace: SET total = 0. SET i = 1. WHILE i <= 4: total = total + i. i = i + 1. OUTPUT total.

Example 4 medium

Trace this code and state the final output: SET n = 1 SET result = 1 WHILE n < 5 SET n = n + 1

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Related Concepts

Iteration For Loop