IGCSE and AS & A Level Pseudocode Online Compiler

A browser-based pseudocode interpreter for Cambridge IGCSE Computer Science (0478/0984/2210) and Cambridge International AS & A Level Computer Science (9618). Write and run pseudocode, practice past-paper questions, and simulate timed exams — all in one place.

Live: pseudocode-compiler.sherlemious.com

Do not host this without written permission

[!CAUTION] The source is public to read. It is not yours to deploy. Hosting, deploying, mirroring, or giving this away needs prior written permission. That includes free, non-commercial, a school, a class, students, and only in one country. The only public copy is the live site above. Full terms: LICENSE. Email [email protected] to ask. Silence is not permission.

Features

• Browser-based Interpreter — Pseudocode is parsed and executed entirely in the browser via an ANTLR4 grammar and a custom tree-walking interpreter. No transpilation. No server round-trip.
• Cambridge 9618 Support — AS & A Level additions include user-defined types, DATE, pointers, sets, BYREF/BYVAL, random-access files, CASE ranges, and classes.
• Interactive Editor — CodeMirror 6 with syntax highlighting, line numbers, error markers, autocomplete, and selectable editor fonts (including a dyslexia-friendly option).
• Command Palette — Ctrl/⌘ K opens a grouped, searchable palette for every action (run, format, open, navigate, links), plus tidy Open and Export menus for examples, files, downloads, and share links.
• Code Formatter — One-click autoformatter re-indents pseudocode to match block structure.
• Python View — Convert pseudocode to equivalent Python on demand, with syntax highlighting and runtime helper shims.
• Flowchart View — Render pseudocode as an auto-laid-out flowchart (React Flow + dagre).
• Trace Table — Variable-by-variable execution trace collected as the program runs — a built-in exam-style dry-run.
• I/O & File Handling — INPUT support with interactive prompts, and OPENFILE, READFILE, WRITEFILE (including random-access records) simulated in browser storage.
• Practice Mode — Curated past-paper questions with faceted filtering and sort, hints, automated test-case grading, model solutions, and a template-vs-scratch start gate.
• Exam Simulation — Timed exam sessions configurable by topic, difficulty, and question count, with results presented as an exam-paper report card.
• Progress & Analytics — Activity heatmap, difficulty/topic breakdowns, and session history tracking.
• Custom Themes — DB-backed theme editor with a live preview and color pickers, managed from the settings panel.
• Authentication — Secure sign-in via Google OAuth, GitHub OAuth, and email/password.
• Onboarding & Nudges — Interactive tours and smart nudges to guide new users.
• Admin Dashboard — Platform analytics, user feedback, and user management.
• Sharing — Easily share code, practice solutions, and exam results via link.
• Premium Gating — Feature flag support for premium content restrictions.

Tech Stack

Layer	Technology
Framework	Next.js 16 (App Router), React 19
Language	TypeScript 5
Styling	Tailwind CSS v4, tailwind-scrollbar
Components	Radix UI, lucide-react / simple-icons, sonner
Editor	CodeMirror 6 (@codemirror/lang-python for Python view)
Parser	antlr4ng v3 (custom ANTLR4 grammar)
Flowcharts	React Flow (@xyflow/react) + dagre layout
Database	PostgreSQL via Neon
ORM	Prisma 6
Auth	Auth.js (NextAuth v5)
Email	Resend
Analytics	PostHog
Markdown	react-markdown, remark-gfm
Theming	react-colorful (custom theme editor)
Testing	Vitest

File Structure

IGCSE-Pseudocode-Online-Compiler/
├── app/                                  # Next.js application
│   ├── prisma/
│   │   ├── schema.prisma                 # Database schema
│   │   ├── seed.ts                       # Seed script
│   │   └── migrations/
│   ├── public/
│   └── src/
│       ├── app/                          # Thin App Router pages & API routes
│       ├── modules/
│       │   ├── interpreter/              # Language runtime (grammar, parser, VM)
│       │   ├── compiler/                 # Playground UI + shared editor kit
│       │   ├── billing/                  # Pricing, Paddle, entitlements
│       │   ├── practice/                 # Practice UI + autograder
│       │   ├── exams/                    # Exam take / author UI
│       │   ├── classes/                  # Classes & assignments
│       │   ├── auth/                     # NextAuth, session UI, email
│       │   ├── admin/                    # Admin gate helper
│       │   ├── progress/                 # Student progress widgets
│       │   ├── telemetry/                # PostHog wiring
│       │   ├── onboarding/               # Tours & nudges
│       │   ├── feedback/                 # Bug report / survey
│       │   ├── share/                    # Share buttons
│       │   ├── docs/                     # llms.txt + docs TOC
│       │   └── content/                  # Built-in examples + FAQ
│       ├── shared/                       # Layout, UI primitives, Prisma, SEO
│       ├── theme/                        # Theme context, presets, validation
│       └── types/
├── README.md
└── LICENSE

Supported Language Features

See pseudocode.md for the full syntax reference.

• Data types — INTEGER, REAL, CHAR, STRING, BOOLEAN
• Variables & constants — DECLARE, CONSTANT
• Assignment — ← or <-
• Arrays — 1D and 2D with custom bounds
• I/O — INPUT, OUTPUT
• Arithmetic — +, -, *, /, ^, DIV, MOD
• Comparison — =, <>, <, >, <=, >=
• Logical — AND, OR, NOT
• Selection — IF/THEN/ELSE/ENDIF, CASE OF/OTHERWISE/ENDCASE
• Iteration — FOR/TO/STEP/NEXT, WHILE/DO/ENDWHILE, REPEAT/UNTIL
• Subprograms — PROCEDURE/ENDPROCEDURE, FUNCTION/RETURNS/ENDFUNCTION, CALL, RETURN
• File handling — OPENFILE, READFILE, WRITEFILE, CLOSEFILE
• String functions — LENGTH(), LCASE(), UCASE(), SUBSTRING()
• Library routines — ROUND(), RANDOM(), INT(), EOF()
• Comments — // single line

AS & A Level (9618) additions

• User-defined types — TYPE records (dot notation), enums (ordinal arithmetic), pointers (^x, ptr^), SET OF + DEFINE
• DATE type — dd/mm/yyyy literals
• Extended CASE — ranges (1 TO 5 :) and multi-value labels
• Parameter passing — BYREF / BYVAL (sticky across following params)
• Random-access files — OPENFILE ... FOR RANDOM, SEEK, GETRECORD, PUTRECORD
• OOP — CLASS/ENDCLASS, INHERITS, PUBLIC/PRIVATE (runtime-enforced), constructor NEW, SUPER, obj <- NEW ClassName(...)
• ELSE IF — accepted as a two-word alias for ELSEIF

One superset grammar covers both qualifications — all syntax is always available, with no mode toggle.

Local Development

These steps are for running the app on your own machine while reading the code or preparing a change to send back here. They are not permission to deploy it, or to offer a running copy to anyone else. See License.

Prerequisites

• Node.js 20+ (required by Next.js 16)
• A PostgreSQL database (or a free Neon project)

Setup

git clone https://github.com/Sherlemious/IGCSE-Pseudocode-Online-Compiler
cd IGCSE-Pseudocode-Online-Compiler/app
cp .env.example .env   # fill in your secrets
npm install
npm run db:migrate     # create tables
npm run db:seed        # optional: seed example questions
npm run dev            # http://localhost:3000

Environment Variables

See .env.example for the full list. Required variables:

Variable	Description
DATABASE_URL	PostgreSQL connection string (pooled)
DIRECT_URL	PostgreSQL direct connection string
AUTH_SECRET	Random secret for NextAuth session signing (openssl rand -base64 32)
AUTH_URL	Your app origin (e.g. http://localhost:3000)
AUTH_GOOGLE_ID / AUTH_GOOGLE_SECRET	Google OAuth credentials
AUTH_GITHUB_ID / AUTH_GITHUB_SECRET	GitHub OAuth credentials
NEXT_PUBLIC_POSTHOG_KEY	PostHog project key (leave blank to disable)
PREMIUM_GATING_ENABLED	Server-side. true gates isPremium questions to paid students / paid-teacher classes (false by default)

Google OAuth Redirect URI Setup

If you see redirect_uri_mismatch, add the exact callback URL in Google Cloud Console:

• Production: https://pseudocode-compiler.sherlemious.com/api/auth/callback/google
• Local: http://localhost:3000/api/auth/callback/google

Also ensure Authorized JavaScript origins include both https://pseudocode-compiler.sherlemious.com and http://localhost:3000.

Useful Commands

npm run db:migrate    # run Prisma migrations
npm run db:seed       # seed the database
npm run db:studio     # open Prisma Studio
npm run lint          # ESLint
npm test              # run the Vitest suite (interpreter, converters, formatter)
npm run test:watch    # Vitest in watch mode
npm run build         # production build

Regenerating the Parser

If you modify src/modules/interpreter/grammar/Pseudocode.g4, regenerate the TypeScript parser:

npm run antlr:generate

The generated files in src/modules/interpreter/generated/ are committed to the repo — do not edit them by hand.

Contributing

Pull requests back to this repository are welcome.

• Fork the repo and create a branch for the change you want merged here
• Write clear commit messages
• Ensure npm test and npm run build pass before opening a PR

A fork is for proposing changes to this repository. It is not permission to publish or host a separate copy. See License.

License

Copyright (c) 2026 Abdelrahman Mohammed. All rights reserved.

You may read the source and run it on your own computer for yourself. You may not host it, deploy it, or offer it to anyone else — including for free, for a school, or in a single country — without prior written permission.

Use pseudocode-compiler.sherlemious.com. To ask for permission, email [email protected].

The full terms are in LICENSE.