Unit 01 — How Programs Work
Big question: How does a computer follow instructions, and how do programmers know whether those instructions are correct?
This unit starts from zero programming experience. You will write short Python scripts, observe their output, trace the order of instructions, and debug errors.
Learning objectives
By the end of the unit, you should be able to:
- Explain how a computer follows a sequence of instructions.
- Write Python
print()statements to display exact messages. - Predict which lines appear first when a program runs.
- Identify comments and explain why Python ignores them.
- Distinguish a syntax error from a program that runs but produces the wrong result.
- Use error messages and careful testing to correct a program.
Lesson and practice sequence
| Step | Read | Practice | Your task |
|---|---|---|---|
| 1 | Instructions and output | First Message | Write a program that displays a message |
| 2 | Sequence and tracing | Startup Sequence | Put instructions in the right order |
| 3 | Comments and debugging | Fix the Messages | Repair broken Python |
| 4 | Cumulative mini-project | Robotics Status | Combine skills independently |
The lesson articles are combined in the printable unit lesson.
Open the browser practice app after you have published the app with GitHub Pages. GitHub’s file viewer itself cannot run this HTML file.
How your work is checked
Each practice has a specific required output. Run your code until you understand what it does, then use Check in the browser. When you submit your files through a pull request, GitHub Actions runs independent output tests. Your work is evaluated on whether it meets the written requirements, not whether you copied a particular example.
Don’t worry about functions, loops, or variables yet: those are taught in later units. The purpose of Unit 01 is to learn how to read, run, change, and debug a program.