Between the raw hardware and the apps you actually use sits the most important program on any computer: the operating system. It is the tireless manager that shares one CPU between hundreds of programs, hands each a private slice of memory, files away your data, and keeps a crashing app from taking the whole machine down with it — all thousands of times a second, without you ever noticing.
This branch opens the black box: processes and threads, how the scheduler decides who runs next,
virtual memory and paging, file systems, and the synchronisation machinery that stops concurrent
programs from corrupting each other. It builds on how a