How code actually runs
By the end of today you can trace what happens between saving a Python file and seeing output: what reads your text, what turns it into instructions, where values live while it runs, and why a compiled language differs from an interpreted one.
YesterdayThis is Day 1. Nothing precedes it, so we start at the bottom: the machine.
TomorrowTomorrow you'll look at values and variables, the things that live in the memory you meet today.
Why this matters
Every confusing thing later traces back to this: why a variable changed unexpectedly, why one language is faster, why a container needs a runtime. Most people skip it and spend years with a fog where this understanding should be.
- Source code
- Interpreter
- Compiler
- CPU basics
- Memory
- Process
Learn it
75 minCopy this into Claude or ChatGPT. It quizzes you before it explains anything, which is deliberate. The resources under it are how you check what it told you.
Today's Master Prompt
Free · sign inA prompt written for this day alone: your level, the exact scope, what to leave out, and an instruction to quiz you before it explains anything. Paste it into Claude or ChatGPT and it teaches you today's material.
Check it against something that is not a model
An assistant can be fluent and wrong, and on a topic you met today you will not catch it. These cover the same ground and were made by people who do this for a living, so they are what you hold the explanation up against. They are other people's work and we only link to them, so judge them for yourself.
6 hand-picked resources
Free · sign inVideos, official docs and articles covering the same ground, each opened and annotated by hand. They are what you check the assistant against on a day you cannot yet catch it being wrong.
Build it
35 minWrite a three-line Python script that assigns two numbers to variables, adds them, and prints the result. Run it. Then paste it into Python Tutor and step through it one line at a time, watching the variables appear in memory. Finally, introduce a deliberate typo (remove a closing parenthesis) and read the error message carefully before fixing it.
Recall it
20 minAnswer out loud, reveal, then mark honestly whether you had it. That score is the only thing on this page you do not get to choose.
5 recall questions
Free · sign inQuestions you answer from memory, then grade yourself against the real answer. The score is carried into the mastery rating below it, so an honest miss cannot quietly become a tick.
Rate it
Completion and mastery are tracked separately. Be honest, because an inflated rating only means the concept resurfaces sooner.
Mastery tracking
Free · sign inRate yourself against five named criteria per concept. Completion and mastery are tracked separately, and anything you rate shakily comes back automatically on a spaced schedule.
Recap
- 01Source code is inert text until another program reads it
- 02Compilers translate ahead of time; interpreters translate as they run
- 03Values live in memory while a process runs, and vanish when it ends
- 04A program is a file; a process is a running instance of it
Your progress
Free · sign inMark days complete, pick up where you left off across devices, and watch completion and mastery diverge. Free, and the account exists only so ninety days of work cannot vanish with a cleared browser.
Extra time
OptionalOptional. Nothing in a later day depends on anything here.
If you have another hour
Look at Python bytecode directly. Run `python -m dis your_script.py` and read the instructions the interpreter actually executes. You will not understand every line. The goal is only to see that a real, simple instruction list exists underneath.