Operating Systems

A process is a program in execution with its own address space, tracked by a process control block; threads are lighter units that share the process’s memory but keep private stacks, and switching between them costs a context switch.

CPU scheduling decides which ready process runs next; algorithms trade off average waiting time, response time and fairness — SJF is optimal for average wait, Round Robin gives good response, and FCFS is simple but risks the convoy effect.

Synchronization coordinates concurrent access to shared data using locks, semaphores and monitors; deadlock arises when all four Coffman conditions hold, and is handled by prevention, avoidance (Banker’s algorithm), detection or recovery.

Memory management gives each process a virtual address space mapped to physical frames through page tables; the TLB caches recent translations, and demand paging with a replacement policy lets the working set exceed physical memory.

A file system organises data into files and directories, using inodes (or a FAT) to track metadata and the blocks a file occupies, and free-space structures plus journaling to allocate space efficiently and survive crashes.