Should I learn C or Rust for exploring operating systems?

Start with C for this particular goal. Most of the operating-system code you’ll be reading and modifying was written in C, so learning it will make existing kernels, libraries, and tools much easier to understand. Working with pointers, manual memory management, and undefined behavior can be uncomfortable, but those concepts teach you what the machine is actually doing and explain many of the problems Rust is designed to prevent.

You don’t have to treat this as an either-or decision. Spend a little time with both, then choose one project and start building or modifying something small. C has a smaller language surface and lets you work directly with the codebases you’re interested in, while Rust has more sophisticated tooling and makes it easier to write new software with stronger safety guarantees. Learn C first if your immediate priority is tinkering with existing operating systems, then add Rust afterward.

If you were creating a new, complex systems project from scratch, Rust would be a stronger candidate because its compiler catches many memory and concurrency errors. But for understanding and changing mature operating-system code, C is the more useful first language. It’s widely used, unlikely to disappear soon, and learning its hazards gives you useful context for evaluating Rust’s design choices.

C is still the most practical entry point for Linux or BSD development. Rust is valuable and may become more common in systems programming, but its use in major operating systems is still developing. Once you understand C and the underlying systems concepts, Rust’s ownership model and safety guarantees will make much more sense. You’ll probably also encounter some assembly, depending on how deeply you go.