BBoeOS

A minimal x86 operating system with a real-mode bootloader (boot.bin) and a paged high-half kernel (kernel.bin) concatenated on disk, plus a shell, VFS (bbfs + ext2), networking stack, self-hosted assembler, and C compiler. Boots in 16-bit real mode, flips into flat 32-bit protected mode with paging, runs the kernel at ring 0 and userland programs at ring 3 in per-program page directories.

Start here

• Getting started — build, boot, run a built-in, add a file, write a tiny C program
• Requirements — external tools the build, the OS image, and the test suites depend on
• Programs — catalog of the executables that ship in bin/

Writing programs

• C subset reference — what cc.py accepts, the libbboeos, and the compiler’s builtin functions

Reference

• Architecture — boot path, post-flip bring-up, ring-3 userland, paging and per-program address spaces, build-time derivation
• Memory map — kernel-side fixed-physical regions and the per-program user-virt layout
• Syscall interface — the INT 30h syscall table with argument-register conventions
• POSIX compatibility — what BBoeOS implements, partially implements, and skips from the POSIX userland / syscall / libc surface
• File structure — file-by-file breakdown of src/ and the host-side build scripts
• Changelog — detailed history of changes by version and date

Source

The canonical instructions for working in the repository live in CLAUDE.md at the repo root. The pages here host the longer reference tables that used to clutter that file.