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<h1>Vision</h1>

<p><i>Own the whole stack: one language, from the compiler to the kernel to the shell.</i></p>

<p>
  <a href="README.md"><b>README</b></a> ·
  <b>Vision</b> ·
  <a href="https://ajhahnde.github.io/Flash/"><b>Tutorial</b></a> ·
  <a href="REFERENCE.md"><b>Reference</b></a> ·
  <a href="COOKBOOK.md"><b>Cookbook</b></a> ·
  <a href="SETUP.md"><b>Setup</b></a> ·
  <a href="VERSIONING.md"><b>Versioning</b></a> ·
  <a href="CHANGELOG.md"><b>Changelog</b></a> ·
  <a href="LICENSE.md"><b>License</b></a>
</p>

</div>

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## The idea

Flash is a systems programming language built for a single, concrete
purpose: to rewrite [FlashOS](https://github.com/ajhahnde/FlashOS) — an
AArch64 bare-metal kernel and its shell — in a language of its own, and
then to compile itself.

Most languages are designed first and find their users later. Flash starts
from the opposite end. It already has a demanding user — a real operating
system that boots on real hardware — and every feature it grows is one that
user needs. The language is shaped by the kernel, not the other way around.

## What "done" looks like

Three layers, all Flash, all the way down:

- **The shell and userland** are written in Flash.
- **The kernel** is written in Flash.
- **The compiler** is written in Flash, and compiles itself.

At that point the stack answers to no language but its own. Zig — the
language Flash is born from and first compiles to — has done its job and
can step aside.

## Principles

- **Earn every feature.** Flash grows only what FlashOS actually needs to
  express. No speculative generality.
- **Never break the running system.** FlashOS boots today, and it must
  still boot after every step of the migration. Continuity is the
  constraint that outranks all others.
- **Coexist, don't rewrite.** Flash and its host language compile side by
  side, module by module. There is no flag day.
- **Readable by a human.** A program written in Flash should be obvious to
  someone who has never seen the language, and the compiler's output should
  be obvious to someone reviewing the migration.
- **Own the understanding.** The goal is not merely to have a language, but
  to understand every layer of it — the same instinct that turned a C
  kernel into a Zig one, and now turns a Zig one into a Flash one.

## Why

FlashOS already proved that a whole stack can be understood end to end.
Flash is the next floor of that ambition: not just understanding the
operating system, but owning the language it is written in.

## Beyond the rewrite

Rewriting FlashOS and self-hosting is the whole of the plan through v1.0. But the
discipline that gets there — a minimal core that earns every feature — is also
what lets Flash reach further afterward. High-level needs (reference counting,
dynamic dispatch, concurrency) are met by *libraries* on that core, not by
growing the language, so the same small language that writes a kernel can, in
time, write ordinary applications. That wider use comes after self-host, never at
its expense: the operating system stays the only feature that has to be earned.

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*This document is the north star — the "why" and the "what". The "how" —
the staged, versioned plan — is tracked separately and evolves as the work
does.*

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