Operating Systems

20-hour Pareto plan for OS knowledge required in software engineering interviews. Covers the concepts that appear in 90% of systems design interviews and backend engineering roles. Operating Systems OS concepts come up in system design interviews and backend engineering roles. Processes vs Threads Process Separate address space IPC (pipes, sockets) High (fork) Isolated Memory Management Deadlock Conditions (all 4 must hold) Mutual Exclusion: Resource held exclusively Hold and Wait: Holding one, waiting for another No Preemption: Can't force release Circular Wait: A waits for B, B waits for A Prevention: Break any one condition. Most common: enforce ordering (always acquire locks in the same order). Virtual Memory Maps virtual addresses to physical addresses via page tables. Enables: Process isolation (each process thinks it has all memory) Paging (swap to disk when RAM is full) Shared libraries (multiple processes share same code pages) Interview Tip "Understanding processes vs threads, deadlock conditions, and virtual memory shows you can reason about system-level behavior — crucial for distributed systems." Python Implementation Java Implementation