ClassicOS

Build License Platform Made with

ClassicOS is a 32-bit Intel x86 operating system built from scratch using C, NASM, and GCC.
Designed for 386, 486, and Pentium-class CPUs, it runs in protected mode, outputs to VGA text mode and serial ports, and supports floppy/HDD boot with basic FAT support.


Features

  • MBR bootloader at 0x7C00
  • Switch to protected mode with GDT
  • A20 gate enabling
  • Simple FAT12/FAT16 disk loader stub
  • VGA text output (0xB8000)
  • Serial COM1 support (0x3F8)
  • Basic kernel (kmain) written in C
  • Makefile-based build system
  • Bootable floppy image for testing in QEMU

⚙️ Requirements

Youll need the following tools installed:

  • nasm
  • gcc (targeting i386)
  • ld
  • make
  • qemu-system-i386

Optional:

  • gdb
  • vncviewer (TigerVNC or similar)

🛠️ Building ClassicOS

Clone and build:

git clone https://github.com/gbowne1/ClassicOS.git
cd ClassicOS
make
Description
An x86 32 biit Operating System for 386, 486, Pentium class (P-60 to 233MHz, Pentium II, P3, P4, etc)
Readme 185 MiB
Languages
C 84.8%
Assembly 11.7%
Makefile 3.5%