Paying at the Machine

The last step: paying. The new variable paid says how much money the driver put into the machine: a 20 EUR note. The machine prints how much was paid and gives back the change. It has 5 EUR notes, 2 EUR coins and 1 EUR coins, and it gives back as few pieces as possible: as many notes as fit, then 2 EUR coins, and the rest in 1 EUR coins. For our car, the output ends like this:

Fee: 6 EUR
Paid: 20 EUR
Change: 14 EUR
5 EUR notes: 2
2 EUR coins: 2
1 EUR coins: 0

When the money isn't enough, the machine gives nothing back and prints how much is missing: Not enough: 1 EUR missing when the driver puts in only 5 EUR. And when the parking is free, the machine gives all the money back.

A tip: how many 5 EUR notes fit into the change, and how much is left over after them? You've answered questions like that with / and % before.

That's the whole project. With just three lessons behind you, you've written the program of a real pay machine: it calculates with whole numbers, makes decisions with conditions and prints a clear receipt. In the next lesson, on loops, you'll learn to make a program repeat statements, so that it could, for example, work out the fees of all the cars that leave the garage in a day.