With only 2000 lines of code, egos-2000 implements every component of a functional operating system. It runs on a $129 small development board with a RISC-V processor. The vision of this project is to help every student from any college or university to read all the code of an operating system.

We use egos-2000 as our teaching operating system at Cornell. It adopts a 3-layer architecture.

• The earth layer implements hardware-specific abstractions.
  • tty and disk device interfaces
  • cpu interrupt and memory management interfaces
• The grass layer implements hardware-independent abstractions.
  • processes, system calls and inter-process communication
• The application layer implements file system, shell and user commands.

The definitions of struct earth and struct grass in egos.h specify the interfaces between these layers.

• an Artix-7 35T Arty FPGA development board
• a microUSB cable (e.g., microUSB-to-USB or microUSB-to-USB-C)
• [optional] a microSD Pmod, a microSD reader and a microSD card (e.g., Sandisk, Samsung or PNY)

For compiling and running egos-2000, please read USAGES.md or watch the tutorial videos (MacOS, Linux or Windows). This document further introduces the teaching plans, architecture and development history.

The RISC-V instruction set manual introduces the privileged registers used by egos-2000. The SiFive FE310 manual introduces the processor used by egos-2000, especially the GPIO, UART and SPI bus controllers.

For any questions, please contact Yunhao Zhang.

Many thanks to Robbert van Renesse and Lorenzo Alvisi for their support. Many thanks to Meta for supporting me with a fellowship. Many thanks to all CS4411 students at Cornell over the years for helping improve this course.