The difference between a coffee
machine and a computer.
We know that a computer can use operations on different types of data,
it's a powerful machine: all those instructions can be programmed on a
computer. On the opposite of coffee machines or washing machines, that
only do one thing. But if a coffee machine can "mechanicly make coffee
from the factory, a computer doesn't know how to do anything. A
computer needs to be programmed" to edit a photo, put it on a blog or
a website... That's why computers need programs.
What's really interesting is that all the programs in the world can
be written using five ingredients, and we will discover those five
ingredients from concrete examples. We will then know how to program
almost every algorithms in the world.