CHAPTER 2
🪟 Operating System
The big boss of the computer. Without it, hardware and apps have no way to talk. This chapter covers what an OS is, the kinds you'll meet, and the Windows tools the exam loves to ask about.
2.1Introduction to Operating System
An Operating System (OS) is system software that acts as an interface between the user and computer hardware. It manages all hardware resources (CPU, memory, disk, devices) and provides a platform where application programs can run.
OS = the manager at a momo shop.
You (the user) tell them "one plate chicken mo:mo". They tell the cook, track the order, remember who's paying, make sure the stove isn't overloaded. You don't care about any of that. You just want momo.
Without the manager, the cook, the waiter, and the cash counter would be yelling at each other all day.
Examples of operating systems
- Desktop/laptop: Windows, macOS, Linux (Ubuntu, Fedora).
- Mobile: Android, iOS.
- Servers: Linux, Windows Server.
- Embedded: RTOS, FreeRTOS (in routers, washing machines, cars).
2.2Types of Operating System
- Batch OS — collects similar jobs in a batch, runs them one after another. No interaction. Old payroll systems. Example: early IBM mainframes.
- Time-sharing / Multi-user OS — multiple users share one computer. Each gets a slice of CPU time. Example: UNIX.
- Multi-tasking OS — one user runs many programs at once (music + Word + Chrome). Example: Windows, Linux.
- Real-time OS (RTOS) — responds within strict time limits. Example: airbag controller, pacemaker, industrial robots.
- Distributed OS — one OS runs across many networked computers, making them look like one big system. Example: Amoeba, modern cluster systems.
- Network OS — manages users and resources across a network. Example: Windows Server, Novell NetWare.
- Mobile OS — built for touchscreens, battery life, cellular data. Android, iOS.
- Single-user single-tasking — only one user, one program at a time. Old MS-DOS.
Batch = cooking 50 plates of the same curry once.
Time-sharing = one stove, many cooks taking 2-minute turns.
Real-time = the airbag must deploy NOW, no "one moment please."
2.3Functions of Operating Systems
- Process management — decides which program runs on the CPU, when, and for how long.
- Memory management — tracks which program is using which RAM, frees memory when they close.
- File management — creates, reads, writes, deletes files; organizes them in folders.
- Device management — talks to keyboard, mouse, printer, USB via device drivers.
- Security & access control — passwords, user accounts, permissions.
- User interface — provides a GUI or command line so you can actually use it.
- Error detection & recovery — spots hardware/software issues and tries to fix or report them.
- Job scheduling — in multi-user systems, decides whose job runs next.
Think of an OS as a traffic cop at a busy Kathmandu chowk.
Someone has to decide who goes, who waits, who gets a ticket, and what to do when a tempo breaks down in the middle. That's every OS function, every second.
2.4Windows Operating System
Windows (made by Microsoft) is the most common desktop OS. You'll be tested on its parts and built-in tools.
2.4.1 Basic Windows elements
- Desktop — the background screen you see after login. Holds icons and shortcuts.
- Taskbar — the strip at the bottom. Shows Start button, running apps, system tray (clock, volume, network).
- Start menu — click the Start button → list of all installed programs + search.
- My Computer / This PC — shows all drives (C:, D:, USB) and lets you browse files.
- Recycle Bin — temporary trash. Deleted files sit here until you "Empty" it — you can still restore them.
- Windows Explorer / File Explorer — the file browser. Navigate folders, copy, move, rename files.
Recycle Bin = your kitchen dustbin.
You threw the roti away, but until the morning trash collector comes, you can still fish it out if you really need it.
2.4.2 Starting and shutting down Windows
- Start — press the power button; BIOS loads, then Windows boots.
- Sign in — type your password or PIN.
- Shut Down — Start → Power → Shut Down. Fully off.
- Restart — shuts down and boots back up. Often needed after installing software.
- Sleep — saves current state to RAM; wakes instantly but uses a little power.
- Hibernate — saves current state to disk; wakes slightly slower but uses zero power.
2.4.3 File Management with Windows Explorer
- Create folder: right-click → New → Folder.
- Copy:
Ctrl+C. Paste:Ctrl+V. Cut:Ctrl+X. - Rename: select file → F2 (or right-click → Rename).
- Delete:
Delete(goes to Recycle Bin).Shift+Delete= permanent. - Search: type in the search box at the top-right of Explorer.
- Navigate: address bar at the top shows the current path (e.g.
C:\Users\Raju\Documents).
2.4.4 Windows applications
- Control Panel — settings hub: change date/time, uninstall programs, manage users, devices.
- Character Map — shows every character a font supports; useful for inserting symbols (©, ±, ½).
- Paint — basic drawing app. Pencil, brush, fill, shapes. Good enough for simple edits.
2.4.5 Finding files/folders and saving the result
Use the Search box (Start menu or File Explorer). You can filter by file type (kind:document), date, size. Once you find what you need, right-click → Open file location to see where it lives, or drag it to the desktop.
2.4.6 Changing Windows settings
- Add/Remove programs — Control Panel → Programs and Features (or Settings → Apps).
- Clear Documents menu — Taskbar Settings → clears the recent-documents list (privacy).
- Customize taskbar — right-click taskbar → Taskbar settings: position, icons, notifications.
- Control Panel items — Display, Mouse, Keyboard, Sound, Network, User Accounts, Date & Time, Region, Devices & Printers.
2.4.7 Creating shortcut icons on desktop
Right-click empty desktop → New → Shortcut → browse to the program/file → Next → name it → Finish. Or: right-click any file → Send to → Desktop (create shortcut).
Shortcut = sticky-note pointing to a file.
Deleting the shortcut doesn't delete the real thing — you just threw away the sticky note.
2.4.8 System tools
- Disk scanning (Check Disk / chkdsk) — scans drive for bad sectors and file-system errors.
- Disk Defragmenter — rearranges scattered file pieces on an HDD so they sit together; faster reads. Not needed on SSDs — in fact, don't run it on SSDs.
- Backup — makes copies of your files in case the main disk dies.
- Restore (System Restore) — rolls your computer back to an earlier working state (like before a bad driver install).
- Format — wipes a drive clean and sets up a fresh file system (FAT32, NTFS, exFAT). Irreversible — everything on the drive is gone.
Defragmenter = organizing a messy almirah.
Over time, your t-shirts end up stuffed into three different drawers. The defragmenter folds them all neatly into one drawer so you find them faster.
(But: SSDs have no drawers — they're more like random-access shelves, so folding wastes their life span.)
2.5Linux Operating System and its uses
Linux is a free, open-source, Unix-like operating system created by Linus Torvalds in 1991. It's open-source — anyone can see, modify, and distribute the source code.
Key features
- Free & open-source — no license fee.
- Multi-user, multi-tasking — many users and programs at once.
- Portable — runs on phones (Android is Linux-based), servers, supercomputers, fridges.
- Secure — strict permissions model; fewer viruses in the wild.
- Stable — servers often run for years without rebooting.
- Customizable — many distributions (distros): Ubuntu, Fedora, Debian, CentOS, Kali, Arch.
Uses of Linux
- Servers — most websites and cloud servers run Linux.
- Supercomputers — nearly 100% of the top 500 supercomputers run Linux.
- Android phones — Android is built on the Linux kernel.
- Embedded systems — routers, smart TVs, car infotainment.
- Development & security — favourite of programmers and cybersecurity professionals (Kali Linux).
- Desktop — Ubuntu, Linux Mint for everyday users.
Windows = a restaurant with a fixed menu. Linux = the same kitchen but with an open recipe book.
You can cook it as-is, swap in different spices, or invent a whole new dish. Both feed you; one gives you more control.
Common Linux commands (bonus — often asked)
| Command | What it does |
|---|---|
ls | List files in a folder |
cd | Change directory |
pwd | Print current directory |
mkdir | Make a new folder |
rm | Delete file |
cp | Copy |
mv | Move / rename |
sudo | Run a command as admin/root |
chmod | Change file permissions |
ps / top | See running processes |
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