Operating Systems and File Management
What this domain tests
Operating Systems and File Management tests process and memory management, scheduling, file systems, paths, permissions and user interfaces. Expect definitions plus small scheduling or path questions.
Core rules
- An OS manages CPU, memory, files, devices and security; it provides an interface between user and hardware.
- A process is a program in execution; states include new, ready, running, waiting, terminated. A thread is a smaller unit sharing process memory.
- Scheduling: FCFS, SJF, priority, round robin. Round robin gives each process a fixed time quantum.
- Virtual memory uses paging/segmentation so logical addresses can exceed physical RAM; excessive page swapping causes thrashing.
- File systems organise directories and files. An absolute path starts at the root; a relative path starts from the current directory. Extensions are naming conventions, not proof of content.
Worked example
Round robin, quantum 4 ms: P1 needs 10 ms, P2 needs 4 ms, both arrive at 0 in order P1, P2. Timeline: P1 runs 0–4; P2 runs 4–8 and finishes; P1 runs 8–12; P1 runs 12–14 and finishes. Completion times: P2 = 8, P1 = 14. Average completion time = (14 + 8)/2 = 11 ms. Reasoning: each ready process gets at most one quantum before the next ready process.
Traps
Do not confuse a shortcut with the file it points to. Do not assume a hidden extension is absent; enable file extensions. Deleting a folder deletes its contents. Round-robin order depends on arrivals, not only process names. Thrashing is not the same as a full disk.