Learn what an Operating System is, explore the Windows graphical interface, manage files and folders, and master essential Linux commands.
Definition: An Operating System (OS) is a system software that acts as an interface between the user and the computer hardware. It manages all hardware resources and provides services for application programs to run.
Without an operating system, a computer is just a collection of electronic components. The OS is the first program loaded when a computer starts (booting). It controls memory, processes, files, security, and connected devices.
Creates, schedules, and terminates processes. Manages CPU time between programs.
Allocates and deallocates RAM to programs. Manages virtual memory and paging.
Organizes files in folders/directories. Controls read, write, and delete permissions.
Controls I/O devices through device drivers. Coordinates access to printers, disks, etc.
Manages user authentication, passwords, access control and protects data from unauthorised access.
Manages network connections, protocols, and communication between computers.
One user, one program at a time. Example: MS-DOS, early Palm OS.
One user, multiple programs simultaneously. Example: Windows, macOS.
Multiple users access the system at the same time. Example: Unix, Linux servers.
Processes data instantly with no delay. Used in aircraft, medical devices, robots.
Designed for smartphones and tablets. Example: Android, iOS.
Runs in a browser, uses cloud services. Example: Google ChromeOS.
Manages network resources across computers. Example: Windows Server, Novell NetWare.
Runs inside another OS using virtualisation. Example: VirtualBox, VMware.
Built into devices like smart TVs, ATMs, washing machines. Example: VxWorks, Embedded Linux.
Manages a group of computers as a single system. Example: Amoeba, Plan 9.
CPU time shared between multiple users/tasks in turns. Example: Unix time-sharing.
Jobs collected in batches and processed sequentially. Example: Early IBM mainframe OS.
Windows is a Graphical User Interface (GUI) based operating system developed by Microsoft. It uses icons, menus, and windows instead of text commands, making it easy for any user to operate a computer without knowing programming.
Installing Windows: Windows is installed from a bootable USB drive or DVD. During installation, the user selects the partition (drive), enters a product key, and sets up user accounts and preferences.
Booting the System: When the computer starts, the BIOS loads the bootloader, which then loads the Windows kernel into RAM. This process is called booting. A cold boot is starting from power-off; a warm boot is restarting.
GUI (Graphical User Interface) allows users to interact with the computer using visual elements like icons, buttons, and menus, instead of typing text commands. GUI standards include consistent layout, WYSIWYG (What You See Is What You Get), cursors, and drag-and-drop.
Fig 2.1 — Windows Desktop Layout
| Icon | Name | Function |
|---|---|---|
| 🖥️ | My Computer / This PC | Shows all drives (C:, D:), connected devices, and system information. |
| 📁 | My Documents | Default folder to save user files like Word documents, spreadsheets. |
| 🌐 | Network Neighbourhood | Shows computers connected to the same local network. |
| 🗑️ | Recycle Bin | Temporarily stores deleted files. Files can be restored or permanently deleted. |
| ⚡ | Quick Launch Toolbar | Area in taskbar for one-click access to frequently used programs. |
| 🔈 | System Tray | Bottom-right area showing time, volume, network, battery status icons. |
| ⊞ | Start Menu | Main menu to open programs, settings, documents, and shut down. |
| 📋 | Task Bar | Horizontal bar at bottom showing open applications and Start button. |
A Dialog Box is a pop-up window that requests user input or displays information before proceeding with an action.
Top bar showing the name of the open file/program. Contains Minimize, Maximize, Close buttons.
Contains drop-down menus like File, Edit, View, Format, Tools, Help.
Vertical and horizontal bars to scroll through content that doesn't fit on screen.
Bottom bar showing current status info like page number, word count, zoom level.
Expands the window to fill the entire screen.
Hides the window to the taskbar without closing it.
Closes the window and exits the program.
Drag the window edges to resize; drag the title bar to move it.
Simple plain-text editor. Open, save, format, find & replace text. File extension: .txt
Rich text editor with basic formatting (bold, colour, alignment). Saves as .rtf or .docx.
Basic image editor. Create/edit images using brushes, shapes, fill, text. Saves as .bmp, .png, .jpg.
Standard, scientific, programmer, and date-calculation modes available.
System settings: display, sound, network, user accounts, programs, date & time.
Create, modify, delete user accounts. Set passwords and account types (Admin / Standard).
File System: The method an OS uses to organise and store files on a storage device. Windows supports NTFS (New Technology File System — supports large files, permissions, encryption) and FAT32 (older, compatible with most devices).
| File System | Max File Size | Features | Used In |
|---|---|---|---|
| FAT32 | 4 GB | Compatible with most OS, USB drives | Pen drives, SD cards |
| NTFS | 16 TB | Permissions, encryption, journaling | Windows system drives |
| exFAT | 16 EB | FAT32 without size limits | Large USB drives, cameras |
Special Files: System files (hidden files needed for OS to boot), configuration files (.ini, .cfg), log files (.log), and temporary files (.tmp).
Backup and Restoration: Windows provides File History and Backup & Restore tools. Users can create restore points (System Restore) to return the system to a previous working state. Always back up important data to an external drive or cloud storage.
Linux is a free, open-source, multi-user, multi-tasking operating system based on Unix. It was created by Linus Torvalds in 1991. Linux is widely used on servers, supercomputers, Android phones, and embedded systems. It is known for its stability, security, and flexibility.
Source code is freely available. Anyone can view, modify and distribute it.
Multiple users can log in and use the system simultaneously.
Runs multiple processes at the same time without slowing down.
Strong permission model. Virus and malware attacks are rare.
Can run for years without crashing. Ideal for servers.
Runs on many hardware platforms — from phones to supercomputers.
Core of the OS. Manages CPU, memory, device drivers and system calls. Directly interacts with hardware.
Command-line interface between user and kernel. Types: Bash, sh, csh, ksh. Interprets user commands.
Hierarchical directory structure starting from root (/). Supports ext4, xfs, btrfs file systems.
System programs and tools — file managers, text editors (vi, nano), compilers, network tools.
A Process is an instance of a running program. Every process has a unique PID (Process ID). Linux can run thousands of processes simultaneously using scheduling algorithms.
A Thread is the smallest unit of a process. A single process can have multiple threads that share the same memory space but run independently.
| Command | Purpose |
|---|---|
ps | Display running processes |
top | Real-time view of all running processes and CPU/memory usage |
kill [PID] | Terminate a process by its PID |
nice | Set priority of a process |
File & Text Commands
cat [file]Display the contents of a file on screen. Example: cat notes.txttail [file]Show the last 10 lines of a file. Useful for log files. Use tail -n 20 for 20 lines.cmp [f1] [f2]Compare two files byte by byte and report the first difference.diff [f1] [f2]Show line-by-line differences between two files — like comparing document versions.wc [file]Count words, lines, and characters in a file. wc -l counts lines only.sort [file]Sort the lines of a file alphabetically or numerically. Output to screen or new file.Directory & File Management Commands
mkdir [dir]Make a new directory (folder). Example: mkdir Documentscd [dir]Change Directory — navigate into a folder. cd .. goes up one level.rmdir [dir]Remove an empty directory. Use rm -r to remove non-empty directories.pwdPrint Working Directory — shows the full path of the current location.cp [src] [dst]Copy a file from source to destination. cp -r copies entire directories.mv [src] [dst]Move or rename a file/directory. Example: mv old.txt new.txtmore [file]View a long file one screen at a time. Press Space to advance, Q to quit.chmod [perm] [file]Change file permissions (read/write/execute) for owner, group, others. Example: chmod 755 script.shUser & Communication Commands
passwdChange the password of the current user. Prompts for old and new password.whoDisplay who is currently logged into the system and when they logged in.whoamiDisplay the username of the currently logged-in user.kill [PID]Terminate a running process by its Process ID (PID).write [user]Send an instant message to another logged-in user on the same system.wall [message]Broadcast a message to ALL logged-in users simultaneously.merge [files]Merge changes from multiple files. Often used with version control tools.mail [user]Send or read email from the command line using the built-in mail utility.newsRead newsgroup articles posted to the system's news server.Linux uses a hierarchical directory structure starting from the root ( / ). Everything in Linux — files, devices, processes — is represented as a file in this tree structure.
| Directory | Contents |
|---|---|
/ | Root — the top-level directory. All other directories branch from here. |
/home | User home directories. Each user gets a folder: /home/username |
/etc | System configuration files (network settings, user accounts, services). |
/bin | Essential command binaries (ls, cp, cat, mkdir, etc.) |
/usr | User programs and utilities. /usr/bin, /usr/lib |
/var | Variable data — log files, databases, mail spools. |
/tmp | Temporary files created by programs. Cleared on reboot. |
/dev | Device files — represents hardware devices (disks, terminals, printers). |
pwd shows your current location; ls lists files in a directory.chmod 755 gives read/write/execute to owner, read/execute to others./. User home directories are in /home.Keyboard shortcuts (hotkeys) allow you to perform actions quickly without using the mouse. Mastering shortcuts greatly improves your productivity in any office environment.
General Windows Shortcuts
Text Formatting Shortcuts (MS Word / WordPad)
1. Which of the following is the correct definition of an Operating System?
2. GUI stands for:
3. The Recycle Bin in Windows is used to:
4. Which Linux command displays the current working directory?
5. Which dialog box control allows only ONE option to be selected at a time?
6. Linux was created by:
7. The keyboard shortcut to Undo an action in Windows is:
8. Which type of OS is used in aircraft control systems where immediate response is critical?
9. Match: The Linux command chmod is used to:
10. True or False: In Windows, Shift + Delete permanently deletes a file without sending it to the Recycle Bin.