Introduction to Operating System: Functions, Types and Booting
What this domain tests
The operating system is system software that sits between the user, the application programs and the hardware. The exam asks you to name its functions, distinguish its types, explain GUI versus CLI, and describe the boot sequence in the correct order.
Core functions
- Process management: creating processes, scheduling the CPU (FCFS, shortest job first, round robin), context switching and termination.
- Memory management: allocating RAM, virtual memory and paging, reclaiming memory when a process ends.
- File management: directory structure, naming rules, access rights, free-space tracking.
- Device management: device drivers, spooling for printers, buffering.
- Security and accounting: user accounts, passwords, permissions, resource logs.
Types
Batch systems group jobs with no user interaction. Multiprogramming keeps several jobs in memory and switches the CPU when one waits for I/O. Time-sharing (multitasking) gives each user or task a time slice, so it feels interactive. Multiprocessing uses two or more CPUs. Real-time systems are deadline-bound (hard or soft). Distributed systems make several networked machines appear as one, and embedded/mobile systems run a single purpose device.
Worked example
You double-click a spreadsheet file. The file manager passes the request to the OS, which checks permissions, locates the file on secondary storage, reserves RAM, loads the spreadsheet program and the file data as a process, records it in a process control block, and gives it CPU time through the scheduler. On saving, the file system writes the blocks and updates the directory metadata. Naming each function in that chain earns full marks.
Traps
- Saying multiprogramming runs two programs at the same instant; on one CPU they interleave.
- Confusing a compiler or interpreter (language translators) with the operating system.
- Describing GUI as 'always faster'; CLI is often faster and scriptable but needs command knowledge.
- Forgetting that a warm boot restarts without switching the power off.