Loops Inside Loops: The Power of Nested Loops

Imagine you are stamping stars onto paper. You stamp 3 stars on one row, then move down and stamp 3 more stars on the next row, then again on the next row. You end up with 3 rows of 3 stars — that is 9 stars in total! You did two sets of repeating: repeating stars across, AND repeating rows down. In coding, we use loops to repeat actions. Today you will discover what happens when you put one loop INSIDE another.

A loop is a block of code that runs again and again a set number of times. For example, a loop that says 'say Hello 4 times' will print Hello, Hello, Hello, Hello. A nested loop is when you place one loop inside another loop. The loop on the outside is called the outer loop. The loop on the inside is called the inner loop. Here is the key rule: every time the outer loop runs ONCE, the inner loop runs ALL THE WAY through from start to finish. Think of it like a clock. The minute hand (inner loop) goes all the way around 60 times for every ONE turn of the hour hand (outer loop). Let's look at a code example written in simple block-style code: REPEAT 3 TIMES ← outer loop REPEAT 4 TIMES ← inner loop draw a dot END REPEAT END REPEAT The inner loop draws 4 dots each time it runs. The outer loop makes the inner loop run 3 times. So the total number of dots drawn is 3 × 4 = 12 dots. To find the total, multiply: outer loop count × inner loop count.