SIMPL

Pseudocode that runs

Everyone who has ever sketched an algorithm has written pseudocode: plain, readable code meant for people, not machines. SIMPL makes it run. Write IF…THEN, FOR…NEXT, WHILE, press Run, and watch your idea come to life — then keep going, all the way to graphics, sound and complete games.

• 🎓 Studying Computer Science at Cambridge IGCSE, O Level or A Level? It runs the official pseudocode exactly as you write it on the exam paper.
• 🌱 Never written a line of code? Start here. SIMPL reads almost like English, forgives mistakes and explains them, and comes with a book that teaches you programming from zero.
• 🔧 Already a programmer? Rediscover the joy of the 80s home computer: switch on, type, run — and minutes later you're drawing on screen and making sounds. Then open up a complete game and a BASIC interpreter, both written in SIMPL, and see how far a small language can go.

✔ Free  ·  ✔ Nothing to install  ·  ✔ Windows & Linux  ·  ✔ Works fully offline

📖 A language and a book, written together

Most languages hand you a reference card and wish you luck. SIMPL comes with a complete introduction to programming — 31 chapters, from your very first OUTPUT to recursion, linked lists, object orientation and games — written hand in hand with the language itself. They were built together, and it shows:

• Always one keypress away. Press F1 and the manual opens right beside your code, with search, bookmarks and a clickable table of contents.
• Every example is one click from running. Each program in the manual has an Open in editor button: read the idea, open it, run it, break it, fix it.
• Every example is tested. Each program in the book is run against the interpreter, output included. If the manual says it works, it works.
• Learn by doing. Exercises from quick practice to real challenges, all with worked solutions — plus guided projects: a quiz game, a Snake game built from scratch, and full tours of the two big programs below.

Whether you're writing your first line of code ever or revising the night before an exam, the manual is the way in.

🧭 Built to help you understand

• Errors that teach instead of scold. Messages in plain words point to the exact line and tell you what to fix. Making mistakes is part of learning — SIMPL won't leave you stuck.
• Watch your program think. Step through it line by line, set breakpoints, and see every variable change as it happens.
• A complete, friendly IDE. Editor with syntax highlighting, interactive console, debugger, light and dark themes. Nothing to configure: open it and start typing.

🚀 From your first program to your first game

The same simple syntax you start with takes you surprisingly far:

• 🎨 CANVAS — windows, drawing, animation and keyboard input
• 🔊 SOUND — notes, melodies and retro chip-style sound effects
• 📦 IMPORT — your own modules, plus a standard library for maths, strings, arrays, data structures and files
• 🧱 Classes, records, pointers, sets, files — the building blocks of real programs

Same language, same rules, same editor, all the way through. The step from "Hello, world" to "my first game" is shorter than you think.

🕹️ See how far it goes

Two complete programs, written entirely in SIMPL — ready to play, read and take apart:

• 🎮 Tetromino Tumble — a full falling-block game, with a 7-bag randomizer, hard drop, levels, music and sound effects.
• 💻 SIMPLR — a working 1980s-style BASIC interpreter, with numbered lines, PRINT, GOTO, GOSUB and a READY. prompt. A programming language written in a programming language: the most direct way to understand how both work.

Every line is commented, and the manual gives each one a chapter of its own. Play first, then open the hood.

🎓 For Cambridge Computer Science students

If you're studying IGCSE / O Level Computer Science (0478, 0984, 2210) or AS & A Level Computer Science (9618), SIMPL speaks your language — literally:

• The whole pseudocode guide, running as specified: DECLARE, ←, CASE OF, multi-dimensional arrays, records, sequential and random-access files, classes and inheritance, pointers, sets, enumerated types.
• Cambridge strict mode flags anything in your program that goes beyond the official guide, with the section it refers to — so you always know what an examiner would recognise as standard pseudocode.
• Your trace tables, filled in for you. The debugger shows every variable changing, line by line — ideal for checking the traces you do by hand.
• A manual that follows the guide. Part I walks through the Cambridge guide step by step, and dedicated appendices map it onto SIMPL and explain every error message in the guide's own vocabulary.

Teachers: SIMPL is a free, offline classroom tool that follows the official guide, with a full manual and exercises students can work through on their own.

🌱 For complete beginners

Never programmed before? That's exactly who SIMPL was made for. No background needed, no maths degree, no complicated setup:

• Code you can read. IF the score is high enough THEN say well done: SIMPL programs read almost like plain English, so you can focus on the ideas instead of fighting strange symbols.
• A book that starts from zero. Chapter 1 begins with your very first program and every chapter builds on the one before, one concept at a time — nothing is used before it's explained.
• Instant feedback. Type a line, press Run, see the result. Get something wrong, and SIMPL tells you where and why, in plain words.
• A real destination. By the end of the book you'll be building your own games — starting with Snake, step by step — and the skills you learn carry straight over to any other language.

🔧 For the curious programmer

Already fluent in Python, C or JavaScript? SIMPL is a small, complete language you can hold in your head — and a pleasant place to play:

• Take an interpreter apart. SIMPLR walks through a lexer, a recursive-descent parser and an execution loop, in code designed to be read.
• Relive the home-computer era. A canvas, a keyboard, square-wave sound and a game loop: everything you need to write an arcade game over a weekend.
• Sketch algorithms the readable way. Try out a sort, a search or a data structure in pseudocode anyone can follow — and have it actually run.
• Teach someone you know. Kids, friends, colleagues: SIMPL and its manual make a gentle, complete first course.

Get started in a minute

1. Download simpl.exe (Windows 10 / 11, 64-bit) or simpl.appimage (Linux, x86_64).
2. Put it in a folder of its own and run it — there's nothing to install.

Built with the people who use it

SIMPL keeps growing, and the best ideas come from the people using it. Found a bug? Have an idea for a feature or a library? Tell me on the community board — every post is read. Wrote something you're proud of? Show it off in Show your programs.

Free. All of it.

Interpreter, IDE, manual, libraries and examples: free to download and use, with no DRM and nothing locked away. If SIMPL helps you learn, teach, pass an exam or build your first game, a small donation helps it keep growing. ❤️