Every Lok Sewa computer question paper, from Kharidar to Computer Operator, asks about the operating system and Windows. This note explains what an operating system does, its types, how a computer starts, the parts of the Windows screen, files and extensions, and the keyboard shortcuts that are asked again and again.
1. What is an operating system?
An operating system (OS) is the main system software that manages the computer hardware and lets users and application programs use it. It is the main program loaded into memory when the computer starts, and it acts as a bridge between the user and the hardware.
- Process management: decides which program uses the CPU and for how long.
- Memory management: gives RAM to programs and takes it back when they close.
- File management: creates, stores, names and organises files and folders.
- Device management: controls printers, keyboards and disks through device drivers.
- Security: protects data with user accounts and passwords.
- User interface: lets the user give commands, by typing or by clicking.
Examples: Microsoft Windows, Linux (Ubuntu, Fedora), macOS, Android and iOS. MS-DOS was an early OS from Microsoft.
2. Types of operating system
| Type | Meaning | Example or use |
|---|---|---|
| Batch OS | Similar jobs are collected and run together without user interaction | Early mainframes, payroll processing |
| Time-sharing (multi-user) | CPU time is shared among many users, so each feels the computer is his own | Unix servers |
| Real-time OS (RTOS) | Responds within a fixed, very short time | Air traffic control, robots, medical machines |
| Distributed OS | Many connected computers work as one system | Large data centres |
| Network OS | Manages a server and the computers connected to it | Windows Server, Linux servers |
| Mobile OS | Made for phones and tablets | Android, iOS |
Interfaces: a CUI or CLI (Character or Command Line User Interface) needs typed commands, as in MS-DOS. A GUI (Graphical User Interface) uses windows, icons, menus and a pointer (WIMP), as in Windows.
Multitasking means running more than one program at the same time. Multiprocessing means using more than one CPU. Multi-user means more than one user can use the system at the same time.
3. Booting: how a computer starts
Booting is the process of starting a computer and loading the operating system from the hard disk or SSD into RAM.
- Cold booting: starting a computer that was fully switched off, by pressing the power button.
- Warm booting: restarting a computer that is already on, for example with Start, then Restart (in MS-DOS, Ctrl + Alt + Delete restarted the computer).
- BIOS (Basic Input Output System), or the newer UEFI, is stored in ROM or flash memory and starts the booting.
- POST (Power On Self Test) checks the RAM, keyboard and other hardware at start-up.
- The boot loader then loads the operating system into memory.
4. Parts of the Windows screen
| Part | What it does |
|---|---|
| Desktop | The main screen that appears after Windows starts |
| Taskbar | The bar at the bottom with the Start button, open programs and the clock |
| Start menu | Opens programs, settings and the power options |
| Icons | Small pictures that stand for files, folders or programs |
| Recycle Bin | Holds deleted files until it is emptied, so they can be restored |
| File Explorer | Shows drives, folders and files (earlier called Windows Explorer) |
| Control Panel or Settings | Changes system settings such as date, users and devices |
| Notification area (system tray) | Shows the clock, volume, network and battery icons |
A file deleted with Delete goes to the Recycle Bin. Shift + Delete deletes it permanently without using the Recycle Bin. Files deleted from a USB drive also do not go to the Recycle Bin.
5. Files, folders and extensions
A file is a named collection of data stored on a disk. A folder (directory) holds files and other folders. A file name has two parts, the name and the extension, for example report.docx. The extension tells Windows which program opens the file. A file name cannot contain these characters: \ / : * ? ” | or the less-than and greater-than signs.
| Extension | File type |
|---|---|
| .docx / .doc | Microsoft Word document |
| .xlsx / .xls | Microsoft Excel workbook |
| .pptx / .ppt | Microsoft PowerPoint presentation |
| Portable Document Format | |
| .txt | Plain text (Notepad) |
| .jpg, .png, .gif, .bmp | Images |
| .mp3, .wav | Audio |
| .mp4, .avi, .mkv | Video |
| .exe | Program (executable file) |
| .zip, .rar | Compressed files |
A path shows where a file is kept, for example C:\Users\Ram\Documents\report.docx. In Windows, C: is usually the drive where the operating system is installed.
6. Important Windows shortcuts
| Shortcut | Action |
|---|---|
| Ctrl + C / Ctrl + X / Ctrl + V | Copy / Cut / Paste |
| Ctrl + Z / Ctrl + Y | Undo / Redo |
| Ctrl + A | Select all |
| Alt + Tab | Switch between open windows |
| Alt + F4 | Close the active window or program |
| Windows key + D | Show the desktop |
| Windows key + E | Open File Explorer |
| Windows key + L | Lock the computer |
| F2 | Rename the selected file or folder |
| F5 | Refresh |
| Ctrl + Shift + Esc | Open Task Manager directly |
| Ctrl + Alt + Delete | Security screen (lock, switch user, Task Manager) |
| Print Screen (PrtSc) | Copy a picture of the screen |
7. Utility programs and drivers
- Antivirus: finds and removes viruses and other malware. Examples: Windows Security (Defender), Avast, Kaspersky.
- Disk Cleanup: removes temporary and unwanted files to free space.
- Disk Defragmenter: joins scattered pieces of files on a hard disk so it works faster (not needed for SSDs).
- Backup: keeps a copy of important data.
- File compression: makes files smaller, for example WinZip, WinRAR and 7-Zip.
- Device driver: a small program that lets the OS work with a device such as a printer.
8. Linux and open source
Linux is a free and open source operating system. Its core, the kernel, was written by Linus Torvalds in 1991. Open source means the source code can be seen, changed and shared. Popular Linux distributions are Ubuntu, Fedora and Debian. Android is built on the Linux kernel. Windows and macOS are proprietary (closed source) systems.
📌 Key points to remember
- The OS manages processes, memory, files, devices and security, and gives the user interface.
- MS-DOS has a command line (CUI); Windows has a graphical interface (GUI).
- A real-time OS is used where a quick, fixed response time is needed.
- Cold boot starts from power off; warm boot restarts a running computer.
- BIOS or UEFI starts the booting, and POST checks the hardware.
- Shift + Delete deletes a file permanently, without the Recycle Bin.
- F2 renames, Alt + F4 closes, Windows + L locks, Windows + D shows the desktop.
- Linux was created by Linus Torvalds in 1991; Android uses the Linux kernel.
Test yourself: Operating System and Windows Basics
Practise What is an operating system?, Files, folders and extensions and Linux and open source with 50 questions. Each attempt picks 25 at random.