← Challenge details
Course previewDay 1 is ready. Tuesday through Friday are still being built.

Before Day 1

4 Concepts to Master

You do not need to understand every line of code. These four concepts give you a simple way to start reading what is in front of you.

Input
What information does the code start with or receive?
Action
What does the code seem to do with that information?
Output
What result seems to come back?
Decision
Where does the code seem to choose between different outcomes?

How the challenge works

  • Each day is one short challenge made up of several tasks.
  • You may start with very little context. That is intentional.
  • Nothing is graded, and you are never expected to understand every line.
  • Treat the timed reads as practice.