APCSP Pseudocode IDE

A full browser-based IDE for AP Computer Science Principles (APCSP) College Board pseudocode. No install, no build step — just open index.html.

Features

IDE

• Syntax highlighting — keywords, builtins, strings, numbers, comments, procedure names all colored distinctly
• Line numbers — gutter that tracks cursor position
• Multi-file tabs — open several files at once, switch between them
• File explorer sidebar with open/close/new file
• Find in file — Ctrl+F, navigate with ↑↓, match counter
• Toggle line comments — Ctrl+/
• Resizable panels — drag the sidebar or console divider
• Save to disk — Ctrl+S downloads the file
• Open from disk — Ctrl+O or File → Open
• Zoom — Ctrl++ / Ctrl+- adjusts font size
• Menu bar — File, Edit, View, Run, Help with keyboard shortcuts
• Status bar — cursor position, language, file encoding
• Pseudocode Reference modal — Help → Pseudocode Reference

Language (full College Board spec)

Feature	Syntax
Assignment	x ← value or x <- value
Display	DISPLAY(x)
Input	x ← INPUT()
If	IF (cond) { }
If / Else	IF (cond) { } ELSE { }
Repeat N times	REPEAT n TIMES { }
Repeat until	REPEAT UNTIL (cond) { }
For each	FOR EACH item IN list { }
Procedures	PROCEDURE name(params) { }
Return	RETURN(value)
Lists	x ← [1, 2, 3]
List index (1-based)	x[1]
Append	APPEND(list, val)
Remove	REMOVE(list, i)
Insert	INSERT(list, i, val)
Length	LENGTH(list)
Modulo	x MOD y
Logic	NOT AND OR
Comparison	= != < > <= >=
Comments	// comment

Usage

1. Clone or download this repo
2. Open index.html in any modern browser
3. Write pseudocode in the editor
4. Press ▶ Run or Ctrl+Enter

Keyboard Shortcuts

Shortcut	Action
Ctrl+Enter	Run
Ctrl+S	Save file
Ctrl+N	New file
Ctrl+O	Open file
Ctrl+F	Find in file
Ctrl+/	Toggle comment
Ctrl+B	Toggle sidebar
`Ctrl+``	Toggle console
Ctrl++ / Ctrl+-	Zoom in / out
Tab	Insert 3 spaces

Architecture

index.html      — page structure, menus, panels, modal
style.css       — VS Code–inspired dark theme (JetBrains Mono)
interpreter.js  — Lexer → Parser (AST) → Interpreter  (pure JS, no deps)
app.js          — UI: tabs, highlight, gutter, find, resize, I/O

The interpreter uses standard compiler stages:

1. Lexer — tokenises source into a flat token stream
2. Parser — recursive-descent parser builds an AST
3. Interpreter — async tree-walk evaluator with lexical scoping

License

MIT