Operating System

When you press the power button, a logo appears, then a desktop or a home screen, and the computer waits for you. The program that does all this, and quietly keeps working until you shut down, is the operating system. It decides which program uses the processor, finds room in memory, saves your files, talks to the printer and asks for your password. This lesson explains what an operating system does, its types, the common ones you will meet, and then the practical skills every computer user needs: working with Windows, managing files and folders, and changing the basic settings.

6.1 Operating system: meaning and functions

An operating system works like the manager of a busy office, or a traffic police officer at a crossroads: it does not do the users' own work, but without it nobody could work at all. Every other program asks the OS for what it needs.

Functions of an operating system

1. Process management. A running program is a process. The OS starts and stops processes and divides the CPU's time among them so quickly that several seem to run at once — this is multitasking (a song plays while you type).
2. Memory management. It gives each program a part of the RAM, keeps programs from using each other's part, and takes the memory back when a program closes.
3. File management. It creates, names, saves, copies, moves, deletes and finds files, and keeps them organized in folders on the disks.
4. Device (input–output) management. Through the device drivers it controls the keyboard, mouse, screen, disks, printer and network, and lines up jobs such as several documents waiting to print.
5. Security and user management. It keeps separate user accounts, checks passwords, PINs, fingerprints or face sign-in, decides who may open which files, and runs a firewall against attacks.
6. User interface. It lets people give commands and see results, either by typing commands or with windows, icons, menus and touch.
7. Booting and error handling. It loads itself when the computer starts and shows a message when something goes wrong, such as a disk being full.

6.2 Types of operating system: single-user and multi-user, CUI and GUI, desktop and mobile

Single-user and multi-user

A single-user operating system lets one user work on the computer at a time. MS-DOS (1981) was single-user and single-tasking: it ran one program at a time. Windows 11 on a home laptop is single-user but multitasking: one person runs many programs at once. (It can hold accounts for several family members, but only one of them works on it at a time.)

A multi-user operating system lets many users work on one computer at the same time, each from a terminal or over the network, while keeping their work separate and secure. UNIX, Linux servers and Windows Server are multi-user; a bank's or university's central computer serves hundreds of users this way.

CUI and GUI

MS-DOS, the Linux terminal (bash) and Windows' Command Prompt and PowerShell are CUIs. Windows, macOS, Ubuntu's desktop, Android and iOS are GUIs.

mkdir School
cd School
touch notes.txt
ls
cp notes.txt backup.txt
ls
mv notes.txt science.txt
ls
rm backup.txt
ls

notes.txt
backup.txt  notes.txt
backup.txt  science.txt
science.txt

Desktop and mobile operating systems

A desktop operating system runs on desktop and laptop computers. It is designed for a keyboard, mouse and large screen, shows many windows side by side, and runs large programs such as office suites and programming tools: Windows, macOS, Linux.

A mobile operating system runs on smartphones and tablets. It is designed for touch, small screens and long battery life; it uses the phone's camera, GPS, sensors and mobile network, and installs apps from an app store: Android and iOS (iPadOS on iPads).

6.3 Common operating systems: Windows, Linux, macOS, Android and iOS

Microsoft Windows. Made by Microsoft. Windows 1.0 came out in 1985; the current version is Windows 11 (first released in 2021, updated every year). It is proprietary and paid, has a GUI with the Start menu and taskbar, runs the largest number of programs and games, and is used on most desktop and laptop computers in the world, including most school labs and offices in Nepal. Ordinary support for Windows 10 ended on 14 October 2025.

Linux. The Linux kernel (the core of the OS) was written in 1991 by Linus Torvalds, a student in Finland, and shared as open source. It is free, can be changed by anyone and is very secure and stable. It comes in distributions (versions put together by different groups) such as Ubuntu, Fedora, Linux Mint and Debian. Linux runs most web servers and almost all the world's supercomputers, and Android is built on it.

macOS. Made by Apple for its Mac computers only (MacBook, iMac). It is proprietary, based on UNIX, known for its smooth design and security, and popular with designers, musicians and video editors. A new version comes every year.

Android. Developed by Google from a start-up it bought in 2005; the first Android phone came out in 2008. It is built on the Linux kernel, its core is open source, and phone makers such as Samsung, Xiaomi, Vivo and OnePlus use it. Apps come from the Google Play Store. Android runs on about seven out of ten smartphones in the world, and on about four out of five in Nepal. The 2026 version is Android 17.

iOS. Made by Apple for the iPhone (first released in 2007); iPads use iPadOS. It is proprietary and runs only on Apple devices; apps come only from the App Store. It is known for long software support and strong privacy controls.

6.4 Working with Windows: desktop, taskbar, Start menu, windows and dialog boxes

Desktop. The screen you see after signing in. It shows a background picture (wallpaper) and icons — small pictures standing for programs, files, folders and the Recycle Bin. An icon with a small curved arrow is a shortcut, a link to a program or file kept elsewhere.

Taskbar. The bar along the bottom of the screen. In Windows 11 it holds, from the middle: the Start button, the Search box, Task View (shows all open windows), pinned and running apps (a small line under an icon means the program is open), and at the right the notification area — network, volume, battery — with the clock and date.

Start menu. Opened by clicking Start or pressing the Windows key. It has a search box, Pinned apps, Recommended recent files, the list of All apps, your account picture and the Power button with Sleep, Shut down and Restart.

Windows. Each program or folder opens in a rectangular window. Its parts: the title bar with the program or file name; the minimize (–), maximize/restore (□) and close (×) buttons; a menu bar, ribbon or command bar of commands; the work area; scroll bars when the content does not fit; and a status bar at the bottom.

Dialog boxes. A dialog box is a small window in which a program asks you for information or a choice before it carries out a command, for example the Print or Font dialog. It contains controls:

1Tabs: each opens a different page of settings2Option (radio) buttons: only one of Foreground and Background can be chosen3Drop-down list: click to choose a theme4Command buttons: Ok, Apply, Cancel and Help

6.5 File management: files, folders, paths and extensions; copy, move, rename and delete; Recycle Bin

Folders inside folders form a tree. At the top of each drive is its root folder, written C:\ or D:\.

File names and extensions. A file name has two parts joined by a dot: the name and the extension, e.g. essay.docx. The extension (2–4 letters after the last dot) tells the operating system the type of the file and which program opens it.

In Windows a file name may be up to 255 characters long but may not contain the characters \ / : * ? " < > |. Two files in the same folder cannot have the same name. To see extensions, open File Explorer → View → Show → File name extensions.

Paths

Linux, Android, macOS and web addresses use the forward slash instead: /home/sita/School/notes.txt.

Working with files and folders in File Explorer

Open File Explorer with Win + E or the folder icon on the taskbar.

The Recycle Bin

• Restore: open the Recycle Bin from the desktop, select the file → Restore the selected items (or right-click → Restore). It returns to the folder it came from.
• Empty: right-click the Recycle Bin → Empty Recycle Bin → Yes. This frees the disk space, and the files cannot be restored from the bin any more.
• Files do not go to the Recycle Bin if they are deleted from a pen drive or memory card, from a network drive, with Shift + Delete, or if they are too large for the bin. Take care with these. (Phones keep deleted photos in a similar Trash or Recently deleted album, usually for 30 days.)

6.6 Settings: date and time, display, user accounts, installing and removing programs

Windows 11 keeps its settings in the Settings app: Start → Settings, or Win + I. (The older Control Panel still exists for some tasks.)

Date and time. 1. Settings → Time & language → Date & time. 2. Turn on Set time automatically so the clock is kept correct over the internet. 3. For Time zone, choose (UTC+05:45) Kathmandu (or turn on Set time zone automatically). Nepal's time is 5 hours 45 minutes ahead of UTC. 4. Click Sync now to correct the clock at once.

Display. 1. Settings → System → Display. 2. Change Brightness, switch on Night light to reduce blue light in the evening, and choose the Scale (100%, 125%, 150%) to make text larger. 3. Keep the Display resolution marked (Recommended) for the sharpest picture. 4. To change the wallpaper or switch between light and dark mode: Settings → Personalization → Background or Colors.

User accounts. Each person who uses a computer should have their own account, with their own files and settings. 1. Settings → Accounts → Other users → Add account. 2. Enter the person's Microsoft account email, or choose I don't have this person's sign-in information → Add a user without a Microsoft account to make a local account with a user name and password. 3. To change it, click the account → Change account type → Standard user or Administrator. 4. Set up a PIN, password or fingerprint in Accounts → Sign-in options.

Installing and removing programs (see Lesson 5). Install from the Microsoft Store or the maker's official website. To remove: Settings → Apps → Installed apps → ⋯ → Uninstall. To stop programs from slowing down start-up: Settings → Apps → Startup and switch off the ones you do not need.

Practice questions

Group A — Objective (1 mark each)

1. The software that manages all the hardware and provides a user interface is [1]aan applicationban operating systemca compilerda driver
2. Running several programs at the same time is called [1]amultitaskingbbootingcformattingdcompiling
3. Which is an example of a CUI? [1]aWindows 11 desktopbMS-DOScAndroiddmacOS
4. GUI stands for [1]aGeneral User InterfacebGraphical User InterfacecGraphics Utility InterfacedGuided User Input
5. Which operating system is open source? [1]aWindowsbiOScLinuxdmacOS
6. Android is developed by [1]aApplebMicrosoftcGoogledSamsung
7. The bar at the bottom of the Windows screen with the Start button is the [1]atitle barbtaskbarcstatus bardscroll bar
8. In a dialog box, the control that lets you choose only one option from a group is the [1]acheck boxboption (radio) buttonctext boxdcommand button
9. In report.pdf, the part pdf is the [1]apathbfoldercextensionddrive
10. The shortcut key to rename a selected file is [1]aF1bF2cF5dF12
11. A file deleted with Shift + Delete [1]agoes to the Recycle Binbis deleted permanentlycis copieddis renamed
12. The time zone used for Nepal is [1]aUTC+05:30bUTC+05:45cUTC+06:00dUTC+05:00

Group B — Short answer (2 marks each)

1. Define operating system. Name two examples. [2]
2. Write any four functions of an operating system. [2]
3. Differentiate between CUI and GUI. [2]
4. Differentiate between single-user and multi-user operating systems. [2]
5. What is a mobile operating system? Name two. [2]
6. Write any two features of Linux. [2]
7. What is a dialog box? Name any three of its controls. [2]
8. Differentiate between a file and a folder. [2]
9. Write the difference between copying and moving a file. [2]
10. What is the Recycle Bin? How can a deleted file be restored? [2]

Group C — Long answer (4 marks each)

1. What is an operating system? Explain any three functions. [1+3]
2. Compare Windows, Linux and Android in a table of at least four points. [4]
3. Draw a labelled sketch of a window in Windows and explain any four of its parts. [4]
4. A folder tree on drive E: has a folder Project containing the folders Photos and Report; Report contains final.docx, and Photos contains trek.jpg.(a) Write the paths of the two files.(b) Write the steps to copy trek.jpg into Report.(c) Write the steps to rename final.docx to science-project.docx. [4]
5. Write the steps to(a) change the time zone to Kathmandu and(b) create a standard user account in Windows 11. [2+2]