I want to build a small operating system as an educational project—to understand how complex software works, practice systems programming, strengthen my résumé, and create a foundation for exploring related areas. My current assumption is that I should learn computer architecture first, then assembly language. Is an operating system primarily written in assembly, or are other languages commonly used? I'd like to eventually understand and implement concepts such as memory allocation, process scheduling, and other basic OS components. What sequence of topics and projects would you recommend? Are there textbooks or resources I could follow in order, starting with computer architecture, continuing through assembly, and then moving into operating-system development?
3 Answers
A good starting point is an operating-system development guide, along with a general OS textbook such as Operating System Concepts by Silberschatz, Galvin, and Gagne or Modern Operating Systems by Tanenbaum and Bos. You can pair those with a computer-architecture text and an assembly-language guide. The important thing is to combine reading with small experiments: boot code, printing text, interrupts, memory management, processes, and eventually scheduling.
You might want to begin with a smaller systems project, such as a text editor, before attempting a full OS. Even a minimal operating system takes a lot of time before it can do anything practical, while an editor gives you visible results quickly and teaches useful skills like input handling, memory management, file formats, and terminal interaction. You could write it in C, C++, or Rust, depending on which ecosystem you want to learn.
An OS is not written entirely in assembly. Most kernels are written mainly in C, C++, or another compiled systems language, with a small amount of assembly for tasks such as bootstrapping, switching CPU modes, handling interrupts, and context switching. Learning assembly is still very useful because it helps you understand what the compiler and processor are doing at the lowest level.
That sounds like a sensible way to build up the necessary skills. What background would you recommend first, and which language would be the best choice for a small editor?