What is Yog?

Yog (योग — union) is a systems compiler that takes JavaScript syntax and produces native machine code. No virtual machine. No garbage collector. No C runtime.

The problem it solves

JS developers who want to target hardware currently have two choices:

1. Learn C/C++ or Rust — a different language with different tooling
2. Use an embedded JS runtime (like Espruino) — which adds a significant interpreter overhead

Yog is a third path: take the JS syntax you already know, apply systems-programming semantics, and compile directly to binary. The JS ecosystem's parser tooling (acorn, babel, etc.) handles the frontend. Yog handles the backend.

Yog vs JavaScript

Yog is not JavaScript. It uses JS syntax as a notation, but:

• There is no garbage collector — memory is managed manually via mmap
• There are no closures, no prototype chains, no this
• There is no standard library — only compiler intrinsics and yog-std
• Types must be explicit (via JSDoc annotations or naming conventions)

Think of the relationship the way AssemblyScript relates to TypeScript: same syntax, completely different execution model.

The compiler: yogc

yogc is the compiler. It takes .yog source files and produces flat binary images:

yogc kernel/kernel.yog kernel8.img
qemu-system-aarch64 -M raspi3b -kernel kernel8.img -serial stdio -display none

Phase 1 targets ARM64 (Raspberry Pi 3 / QEMU raspi3b). Phase 8 adds an LLVM IR backend, giving every architecture LLVM supports.

The demo: JSOS

JSOS is a bare-metal operating system written entirely in Yog — no C, no assembly. It's the primary demonstration that Yog works. The phases in this documentation track JSOS's development from a blinking UART to a self-hosting OS.

But JSOS is just one thing you can build. Yog can target any bare-metal ARM64 system.

Next steps

• Getting Started — install and compile your first .yog file
• The Yog Dialect — what's supported, what's not, and why