I want to build a small operating system as an educational project—to understand how complex software works, practice systems programming, create something useful for my résumé, and explore related areas of computer science. My goal is not to create a production-quality desktop OS, but to implement basic versions of concepts commonly covered in an introductory operating-systems course, such as memory allocation, processes, scheduling, system calls, and simple drivers. I'm unsure how computer architecture, C or C++, assembly, compilers, libraries, debuggers, and operating-system development fit together. Should I learn computer architecture first, followed by assembly, and then OS development? Are there textbooks or structured resources that cover this progression, either in one book or as a sequence? What practical steps and tools would you recommend for starting a simple OS project?
3 Answers
Start with C, basic data structures, computer organization, and a little assembly rather than trying to learn every part of an OS at once. A practical sequence is: learn C and debugging, study how CPUs and memory work, learn enough assembly to read compiler output and write small routines, then learn about linkers, object files, boot processes, and cross-compilers. After that, build a tiny kernel that boots in an emulator, prints text, handles interrupts, manages memory, and eventually supports processes and system calls. You do not write the entire OS in assembly; most kernels are written in C or C++, with assembly used for startup code, context switches, interrupt entry, and other hardware-specific pieces. A useful resource chain is *Computer Systems: A Programmer’s Perspective*, *Operating Systems: Three Easy Pieces*, and the xv6 source code and accompanying text. The Nand2Tetris course is also a good guided introduction because it lets you build a simple computer system from logic gates through a small operating system.
Keep the first target extremely small. Use an emulator such as QEMU and a documented architecture, then create a cross-compiler so your host system’s libraries and assumptions do not accidentally get mixed into the kernel. A normal compiler can generate code for an OS, but the kernel cannot simply rely on the host’s standard library or system calls. You will need a freestanding environment, a linker script, startup code, a boot method, and your own minimal runtime support. Libraries, debuggers, and drivers are definitely part of the larger picture, but you can begin with serial output, a timer, keyboard input, and a simple block device rather than trying to support everything at once.
A sensible project progression would be: boot and display a message; set up a compiler and linker; add exception and interrupt handling; implement a physical-page allocator and kernel heap; add virtual memory; create a basic scheduler and user-mode processes; implement system calls; then add a tiny file system and shell. At each stage, test in an emulator and keep the code in small milestones. Studying an existing teaching kernel such as xv6 is often more useful than attempting to design every subsystem from scratch, because it shows how the pieces connect while remaining small enough to read.
That helps clarify the order. I was assuming I needed to master all of computer architecture and assembly before writing any code, but starting with a small emulator-based kernel and learning each required topic along the way sounds more manageable.