# Operating Systems: Three Easy Pieces

OS textbook from the Arpaci-Dusseaus (UW–Madison), free online at [pages.cs.wisc.edu/~remzi/OSTEP](https://pages.cs.wisc.edu/~remzi/OSTEP/). The "three easy pieces" are virtualization (CPU, memory), concurrency (threads, locks, condvars, semaphores), and persistence (I/O, file systems, journaling, distributed FS). Chapter-per-concept, conversational tone, build-as-you-read. Currently being read by the [[eatonphil-bookclub]] (2026): [cohort page](https://eatonphil.com/2026-ostep.html).