OS

page table structures, two-level and multi-level page tables, TLB, page fault handling

page replacement algorithms, frame allocation, thrashing, working set, shared memory, COW, mmap

I/O hardware, I/O devices, polling, interrupts, DMA, and I/O software layers

secondary storage, HDD structure, disk performance, disk scheduling algorithms

file system basics, mapping problem, directories, mounting, disk layout, VFS internals