A program you can read

Here is a tiny program written in ordinary words. Its job is to count a stack of cards.

set the counter to 0
read the next card
if there is no card, stop
add 1 to the counter
go back to step 2

Read it slowly and you can follow the work in your head. Each line says what happens next.

Many programs work like this: a person writes an exact procedure and the computer follows it. If the answer is wrong, someone can inspect the steps and find the mistake.

Later, we will meet tasks where nobody knows how to write all the necessary rules. That problem changes the story of computing.