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yhzhang0128/egos-2000

A teaching operating system with about 2,000 lines of C and RISC-V assembly, designed so students can read all of its code.

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What is it?

egos-2000 is a teaching operating system written in C and RISC-V assembly, with the whole codebase kept to about 2,000 lines. Its goal is to let a student read every line of a working OS, covering device interfaces, memory management, timers, processes, system calls, a file system, and a shell.

The system is organized into three layers. The earth layer abstracts hardware such as the tty, disk, timer, and memory, the grass layer provides hardware-independent process control and system call interfaces, and the application layer contains the file system, shell, and user commands. The layer interfaces are defined as `struct earth` and `struct grass` in the header egos.h.

It runs on both the QEMU emulator and RISC-V boards. The project is paired with the EGOS book, which contains nine course projects built on the codebase.

Key features

  • 01Implements the core components of an OS in about 2,000 lines of code
  • 02Runs on the QEMU emulator and RISC-V boards
  • 03Three-layer design separates hardware, process/syscall, and application code
  • 04Includes a file system, shell, and user commands
  • 05Accompanied by the EGOS book with nine course projects

Use cases

  • Learning how an operating system works from the hardware interface up
  • Teaching an OS course where students read and extend a complete small kernel
  • Porting an OS to a new RISC-V board or processor implementation

Quick start

  1. 1

    Read USAGES.md for instructions on running egos-2000

Things to know

  • The license is not identified in the metadata, so reuse terms are unclear.
  • It runs only on QEMU and RISC-V boards, not on other hardware.
  • It is a teaching OS with about 2,000 lines of code, not a production operating system.

Topics

#operating-system#risc-v#education#qemu#kernel

FAQ

What is egos-2000?
A teaching operating system with about 2,000 lines of C and RISC-V assembly, designed so students can read all of its code. egos-2000 is a teaching operating system written in C and RISC-V assembly, with the whole codebase kept to about 2,000 lines. Its goal is to let a student read every line of a working OS, covering device interfaces, memory management, timers, processes, system calls, a file system, and a shell.
Is egos-2000 free to use? What license does it have?
egos-2000 is open source under the Other license. Check the license terms before using it in commercial products.
Is egos-2000 still maintained?
Updated within 6 months. The last commit to egos-2000 was on Aug 16, 2026.
What can I use egos-2000 for?
Learning how an operating system works from the hardware interface up Teaching an OS course where students read and extend a complete small kernel Porting an OS to a new RISC-V board or processor implementation
How do I install egos-2000?
Read USAGES.md for instructions on running egos-2000
Where can I get egos-2000?
The source code and installation instructions are on GitHub: https://github.com/yhzhang0128/egos-2000

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