learnFORTH

It's time to learn Forth, the compact stack-based language that powered navigation computers, embedded systems, and a generation of hands-on hackers - and still runs the boot firmware on some retro Sun and Apple hardware. If you ever saw a Jupiter ACE home computer, now is your change to learn about what made it special.

This app teaches you to think in words and stacks with 90 short, structured daily lessons, a live REPL you can experiment in right on your phone or iPad, and hands-on exercises with hints (not answers) so you actually learn the ideas.

WHAT'S INSIDE

• 90 guided lessons across 7 topics: the data stack, words & variables, control flow, loops & recursion, advanced words, data structures, and advanced topics.
• A built-in REPL with syntax highlighting so you can type real FORTH and see the stack respond immediately.
• Exercises for every lesson, graded on output, with an optional hint if you get stuck.
• Daily streaks and per-category progress tracking to keep you moving. You'll learn, promise!
• A plain-English primer on Reverse Polish Notation and stack manipulation (DUP, DROP, SWAP, OVER, ROT) for complete beginners.
• Historical notes on FORTH's dialects - fig-FORTH, Forth-79, Forth-83, ANS Forth - and which one this app's interpreter follows.
• A tip-of-the-hat to the Jupiter ACE, the British home computer from the 1980s that was based on Forth.
• A recommended reading list of classic FORTH books, including Starting FORTH and Thinking Forth by Leo Brodie.
• Light, dark, and automatic themes.

No prior programming experience required. If you've ever wondered how a language with almost no syntax can still get real work done, learnFORTH will show you, one word at a time.

Note: This app is free, with all features always available. If you enjoy it, please use the tip feature to thank the author and encourage future development.