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Final Exam

December 11–17 — in the registrar's assigned slot

Check the official final exam schedule for the exact date, time, and room. It is set by the registrar, not by the course.

Format

Pencil and paper, closed book. One permitted reference: the Cheatsheet, printed. No electronic devices.

Worth 20% of the course grade.

Scope

Cumulative, weighted toward 49k–53k. Everything from both midterms may appear as a building block. The new material — and the bulk of the exam — is:

  • exec and program loading: building a fresh address space, copying the image, mapping a stack, pushing argv, and pointing the trapframe at the entry point
  • File descriptors: the fd as an unforgeable capability the kernel translates; the per-process fd table vs the system-wide open-file table; why sharing an offset between them makes dup and inheritance work; fds 0/1/2; reference counting
  • fork, exit, wait: the call that returns twice; what a child inherits vs copies; zombies and reaping; the process tree and reparenting; why wait exists
  • fork + exec together: why Unix splits process creation in two, and what that split makes possible that a single spawn would not
  • Userland: init as pid 1, and what it means for the shell to be an ordinary unprivileged program
  • Pipes, at the design level only: a bounded ring buffer behind two descriptors; blocking; how a | b falls out of fork + dup + exec. 55k_pipes is extra credit and no question depends on having built it

The question you should expect

There is always one long question that walks a single operation through every layer of the system. Past form: trace rv6$ ls from the keypress that finishes the line to the moment ls exits, naming at each step which component acts, which CSR or data structure is involved, and what the alternative would have cost.

Prepare for it by being able to tell that story out loud. If you can narrate the whole path — console interrupt, line assembly, shell read, fork, exec, address space construction, sret into user mode, the write syscall, exit, wait — you are ready for the exam regardless of what else is on it.

How to prepare

  1. Do Practice Set 3 on paper. It is built from the final's material specifically.
  2. Reread rv6 Architecture end to end. It is the single best revision document in the course.
  3. Boot your own kernel and drive it. Being able to picture what actually happens when you type at the prompt is worth more than another read-through.
  4. Skim Key Concepts as a final checklist.