Decision trees

A single IF handles a single question. But real decisions stack up.

Should I cycle to school? Well — is it raining? If no, is the cycle working? If yes, is there time?

Each answer leads to the next question, and eventually to an outcome. Draw that out and you get a decision tree: questions at the branches, outcomes at the ends.

A decision tree has two kinds of points:

• Branch points are yes/no questions. Every branch splits into exactly two paths.
• Leaves are the endings — the actual decision, with no more questions.

You always start at the top and follow one path down. You never visit two branches at once, and you always finish at exactly one leaf. That's what makes a tree reliable: every possible situation leads somewhere definite.