Loops with Memory

Counters, totals and off-by-one

An interactive lesson with 7 steps, about 6 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• An accumulator starts at 0 and a loop keeps adding to it.
• range(a, b) runs from a up to b − 1: b − a values.
• Off-by-one (fencepost) errors hide in loop limits; test small cases.

Steps

1. Running totals
2. Adding squares
3. Reaching 55
4. Fenceposts
5. How many times?
6. The biggest so far
7. Counting multiples