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☰Spec✉Source
?WIKI
*** 2026-09-30: spec2 drafted *** Now working on P1: first pixels on screen & PCI device listing *** No BIOS required ***

LWOS: Every byte by hand.

What is LWOS?

A hobby operating system for CNC milling machines. It looks and feels like an IBM PC, but it doesn't depend on the BIOS.

LWOS loader reading FAT32, then the MONITOR prompt
From power-on to the MONITOR prompt (illustration)

Under constructionUNDER CONSTRUCTION
v2 is an early rewrite. APIs and layout may change without notice.

Flat memory, hardware tasks

No paging and no page tables. Everything lives in one flat 4 GB address space, so a C pointer is a physical address you can hand straight to a DMA engine. Each task gets a TSS descriptor in the GDT, and the timer switches between them with a far jump.

Memory map from 0 to 4 GB beside the GDT; the timer jumps between TSS entries for MONITOR, task A and task B
One address space, three tasks, no walls. Multitasking is planned for P7 (illustration)

What works today NEW!

  • MBR boot with partition table
  • Read-only FAT32 in the loader
  • mkfat, a host tool for building FAT images

Coming next: a DEBUG.COM-style monitor, an EDIT.COM-style editor, and the CNC stack.

Build & run

You need make, a C compiler, and QEMU or Bochs.

git clone https://github.com/LWOS-dev/lwos
cd lwos
make run

Get the source... Read the wiki

LWOS now!Best viewed in BochsBIOS-freePowered by make runx86 32-bit protected mode

LWOS

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