Do you know how you tie your shoelaces?

“Of course! I do it every day” – you must be thinking.

No, no, no. I assume you can tie your shoelaces. What I wonder is if you know how do you do it. Could you describe it step by step, in words or pictures? That’s another kettle of fish… You are not allowed to test it. You can not even look at your shoes. How do you move each finger at every step?

If you can describe how to tie shoelaces, it’s probably because you had to teach someone how to do it.

Something similar happens with programming. We have to teach the computer how to perform tasks that we can do. But we have to describe them in detail, in a very limited language. Nothing is understood implicitly by the computer. We often find ourselves thinking hard to separate the elementary steps of a process that we perform automatically, almost unconsciously.

Therein lies one of the difficulties of programming. The other difficulty is that, expanding the analogy, we need the computer to do all known sailor knots… and some more.