Class 11 Computer Science – Unit 3: Computer Software and Operating System
This unit provides a comprehensive overview of Computer Software and Operating Systems, covering different categories of software, functions of operating systems, Windows environment, open-source systems, and mobile operating systems. Understanding these concepts is crucial for computer science applications and forms the foundation of software management and system operations.
Unit Information
Unit 3: Computer Software and Operating System (12 hours)
Subject: Computer Science, Grade 11, NEB
Description: This guide provides complete notes covering software categories, operating systems, Windows environment, Linux, and mobile OS as per NEB syllabus.
Credit: Important Notes
Table of Contents
Detailed Unit Notes
3.1 Concept of Software
3.1.1 Definition of Software
Software is a set of programs written for a computer to perform a particular task. A program is a sequence of instructions, and an instruction is a command given to the computer to perform certain tasks on given data.
A computer has no use without software. The computer would be a metallic box if there were no software. Software is the interface between the computer and the user. It is a group of commands that tells the computer what to do and how to do it.
3.1.2 Categories of Software
1. System Software
Software used to control and coordinate computer hardware and other software is called system software. It is responsible for resource management, task management, file management, memory management, and language translation management.
Classification of System Software:
- Operating System – Acts as an interface between user and hardware (Windows, Mac, Linux, MS-DOS)
- Language Translator – Converts statements between different languages
- Assembler
- Compiler
- Interpreter
- Device Drivers – Controls particular hardware devices (display drivers, printer drivers, USB drivers)
2. Utility Software
Software designed to maintain computer hardware and software. It provides additions to the capabilities provided by the operating system.
Examples: Antivirus software, backup utility, disk checker, file manager, disk cleaner.
3. Application Software
User-oriented software used to solve particular problems for users and make user tasks easier. It is used by users to perform specific tasks.
Types of Application Software:
- Package Software – Generalized programs for general purpose use (Word processing, database management, graphics)
- Tailored Software – Developed according to specific user/organization needs (School management system, hospital management system)
4. Web-based Software
Software accessed over a network connection using HTTP rather than from within a memory device. It often runs inside a web browser.
Examples: Online games, online shopping, Google Docs, webmail services.
5. Mobile Application Software
Software developed specially for use on small wireless devices such as smartphones, tablets, etc.
Examples: Mobile games, social media apps, productivity apps, navigation apps.
3.2 Concept of Operating System
3.2.1 Introduction and Role of Operating System
An Operating System (OS) is a set of programs that manages computer hardware resources and provides common services for application programs. It controls the overall actions and acts as a mediator between the user and the computer hardware. It is the backbone of a computer system.
Relationship Diagram:
User <=> Application Program <=> Operating System <=> Hardware
Roles of an Operating System:
- Accept input from users through input devices
- Send output to output devices
- Help users to develop programs
- Deal with faults and inform the operator
- Provide platform for other application programs
- Store and manage files and applications in memory
3.2.2 Functions of an Operating System
- Processor Management – Manages processes and threads, allocates system resources to processes
- Memory Management – Manages computer’s primary memory, allocates and deallocates memory
- Input/Output Management – Coordinates and controls input/output devices
- File Management – Creates and organizes files, folders, and directory hierarchy
- Security Management – Provides user accounts, passwords, and encryption facilities
- Controlling Resources – Manages shared resources like printers and hard disks
- Time-sharing – Provides time slices to multiple terminals
- User Interface – Allows communication with the OS
- Error Handling – Detects and handles errors like HDD failure, memory overflow
- Virtual Storage – Manages virtual memory and storage allocation
3.2.3 Operating System Terminology
| Term | Definition |
|---|---|
| Kernel | Core component of the OS that manages system resources |
| Process | Program in execution |
| Thread | Smallest unit of processing that can be scheduled |
| Multitasking | Ability to run multiple tasks simultaneously |
| Multiprocessing | Using multiple processors for task execution |
| Virtual Memory | Memory management technique that uses disk space as RAM |
| File System | Method for storing and organizing computer files |
| Device Driver | Software that controls a hardware device |
3.3 Windows Operating System
3.3.1 Introduction to GUI based Operating System
GUI (Graphical User Interface) allows users to enter commands by clicking and pointing at objects that appear on the screen. It takes advantage of computer graphical capabilities to make programs easier to use.
Features of GUI:
- Easy to operate and user-friendly
- No need to remember commands and syntax
- Requires larger space and faster processor
- Usually 32 or 64 bits
- Capable of multi-tasking, multi-programming, and multi-user systems
Examples: Windows, Mac OS, iOS
3.3.2 Working in Desktop Application and Window Environment
Desktop Application: A software program that runs locally on a desktop or laptop computer, installed directly onto the operating system.
Examples: Microsoft Office, Adobe Photoshop, video games
Windows Environment Components:
- Desktop: Main screen area with icons and background
- Taskbar: Bar at the bottom with Start button and running apps
- Start Menu: Access point for programs and settings
- File Explorer: Tool for managing files and folders
3.3.3 Manage Files and Folders with File Explorer
Creating a Folder:
- Open File Explorer
- Navigate to desired location (Desktop or Documents)
- Right-click on empty space
- Select “New” → “Folder”
- Type name and press Enter
Creating a File:
- Right-click on empty space
- Select “New” → “Text Document” (or other file type)
- Rename the file as needed
3.3.4 Customize the Start Screen and Desktop
Customizing Desktop:
- Right-click on empty desktop area
- Select “Personalize”
- Change background, colors, and theme
- Use “View” menu to change icon size and arrangement
Customizing Start Screen/Menu:
- Open Start Menu
- Resize by dragging edges
- Pin apps by right-clicking and selecting “Pin to Start”
- Drag tiles to rearrange or right-click to resize
3.3.5 Installing and Removing Devices
Installing a Device:
- Most devices use “Plug and Play” – connect and OS auto-detects
- If not detected automatically: Settings → Devices → “Add a device”
Removing a Device:
- Settings → Devices
- Select device to remove
- Click “Remove device” and confirm
3.3.6 Manage Passwords and Privacy Levels
Password Management:
- Use strong passwords (12+ characters with mix of characters)
- Use unique passwords for each account
- Set up Windows Hello (PIN, fingerprint, facial recognition)
Privacy Settings:
- Settings → Privacy
- Control app access to camera, microphone, location
- Manage personal data access
3.3.7 Use of Control Panel, System Tools and Accessories
Control Panel:
- Access by searching “Control Panel” in Start Menu
- Manage system settings, programs, and security
System Tools:
- Found in “Windows Administrative Tools”
- Task Scheduler (automate tasks)
- Performance Monitor (view system performance)
Accessories:
- Basic built-in applications
- Notepad (text editor), Paint (image editor), Calculator
- Found in Start Menu’s app list
| Shortcut | Function |
|---|---|
| Ctrl + C | Copy |
| Ctrl + V | Paste |
| Ctrl + X | Cut |
| Ctrl + Z | Undo |
| Ctrl + A | Select All |
| Ctrl + Y | Redo |
| Shift + Delete | Permanently delete |
| Ctrl + S | Save |
| F2 | Rename |
| F3 | Search |
| Alt + F4 | Close window |
3.4 Open Sources and Mobile Operating System
3.4.1 Concept of Open Sources Operating System
Open-source software follows a methodology where source code is made publicly available. Users can view, modify, debug, and redistribute the code.
Characteristics:
- Source code is publicly accessible
- Free to use, modify, and distribute
- Community-driven development
- Transparent and collaborative approach
Examples: Linux, Unix, OpenSolaris
3.4.2 Introduction to Linux and UNIX
UNIX:
- Multi-user, multi-tasking, multi-processing, time-sharing OS
- Originally developed in 1969 by AT&T and Bell Communication
- First in assembly language, reprogrammed in ‘C’ in 1973
- Flexible OS used for various processor types
- Widely used in servers, now also in PCs and mobile devices
LINUX:
- Open-source, powerful, Unix-based OS
- Developed by Linus Torvalds (University of Helsinki, Finland)
- Released as college project with source code
- Uses 95% ‘C’ programming language and 5% other languages
- Runs on various platforms (PC, laptop, mobile, supercomputers)
3.4.3 Linux Distributions
Linux is just a kernel. Linux distributions combine the kernel with other free software to create complete operating systems.
Popular Linux Distributions:
- Ubuntu: User-friendly, great for beginners
- Fedora: Cutting-edge features, sponsored by Red Hat
- Red Hat Enterprise Linux: Commercial distribution for enterprises
- Debian: Stable, community-driven distribution
- MX Linux: Lightweight, efficient distribution
- Gentoo: Highly customizable, source-based distribution
Note: Almost 600 Linux distributions exist, with about 500 in active development.
3.4.4 Concept and Types of Mobile Operating System
A mobile OS is specially designed to run on mobile devices (smartphones, tablets, PDAs, wearables). It manages hardware and enables user-friendly app operation.
Android OS
- Developer: Google, Huawei, Baidu
- Release Date: September 23, 2008
- Programming Language: Java, C, XML, Assembly
- Features: Uses Linux 2.6 for core services, open and free software stack
iOS (iPhone OS)
- Developer: Apple Inc.
- Release Date: June 29, 2007
- Programming Language: Swift, C++, C, Objective-C
- Features: Used on iPhone, iPad, iPod; closed-source
BlackBerry OS
- Developer: BlackBerry Ltd.
- Release Date: November 2013 (BlackBerry 9720/9900)
- Programming Language: C++, Java
- Features: Popular with corporate users, syncs with Microsoft Exchange
Windows Phone OS
- Developer: Microsoft Corporation
- Release Date: October 21, 2010
- Programming Language: C++, C
- Features: Based on Windows CE 5.2 kernel
Symbian OS
- Developer: Nokia, Symbian Ltd.
- Release Date: 1997
- Programming Language: C
- Features: High integration with communication and PIM functionality
Practice Questions and Answers
Question 1: Explain software with its categories.
Answer: Software is a set of instructions, data, or programs used to operate computers and execute specific tasks. It is the intangible part of a computer system. The main categories are:
- System Software: Manages computer hardware and provides platform for application software (OS, device drivers, utilities)
- Application Software: Designed for end-users to perform specific tasks (word processors, web browsers, games)
Question 2: State the concept of operating system with its functions.
Answer: An operating system (OS) is the core system software that manages all computer hardware and software. It acts as an intermediary between the user and the hardware.
Functions:
- Memory Management: Allocating and managing RAM
- Process Management: Managing tasks and CPU processes
- File Management: Organizing files and folders
- Device Management: Controlling peripheral devices
- Security: Providing user accounts and passwords
Question 3: Describe GUI based operating system and its features.
Answer: A GUI (Graphical User Interface) based operating system allows users to interact with the computer using visual elements like icons, windows, and menus.
Features:
- Windows: Rectangular areas displaying information
- Icons: Pictures representing files and applications
- Menus: Lists of options and commands
- Pointer: On-screen symbol controlled by mouse
Question 4: Introduce desktop application and windows environment.
Answer:
Desktop Application: Software program running locally on computer, installed directly on OS (Microsoft Office, Adobe Photoshop).
Windows Environment: Graphical interface components including Desktop, Taskbar, Start Menu, and File Explorer.
Question 5: Create file and folders with file explorer.
Answer:
Create Folder: Open File Explorer → navigate to location → right-click empty space → New → Folder → type name → Enter.
Create File: Right-click empty space → New → Text Document → rename file.
Question 6: Customize the start screen and desktop.
Answer:
Desktop: Right-click empty area → Personalize → change background, colors, theme.
Start Screen: Open Start Menu → resize edges → pin apps by right-clicking → drag to rearrange.
Question 7: Install and remove the devices.
Answer:
Install: Connect device (Plug and Play) or Settings → Devices → Add device.
Remove: Settings → Devices → select device → Remove device → confirm.
Question 8: Manage password and privacy.
Answer:
Passwords: Use strong passwords (12+ characters with mix), unique for each account.
Privacy: Settings → Privacy → control app access to camera, microphone, location.
Question 9: Use control panel, system tools and accessories.
Answer:
Control Panel: Search “Control Panel” → manage system settings, programs.
System Tools: Windows Administrative Tools → Task Scheduler, Performance Monitor.
Accessories: Notepad, Paint, Calculator in Start Menu app list.
Question 10: State the concept of open sources and mobile operating system.
Answer:
Open-Source Software: Software with publicly available source code that can be viewed, modified, and distributed (Linux).
Mobile Operating System: OS designed for mobile devices, managing hardware and providing platform for mobile apps (Android, iOS).
Question 11: Introduce Linux, UNIX and Linux distribution.
Answer:
UNIX: Family of multitasking, multiuser OS from 1970s, basis for modern OS including macOS.
Linux: Open-source OS kernel created by Linus Torvalds, inspired by UNIX.
Linux Distribution: Complete OS built around Linux kernel with desktop environment and applications (Ubuntu, Fedora).
Question 12: Explain the types of mobile operating system.
Answer:
Android: Open-source OS by Google based on Linux, most widely used, flexible.
iOS: Closed-source OS by Apple for iPhone/iPad, user-friendly, secure.
Others: BlackBerry OS (corporate use), Windows Phone (Microsoft), Symbian (Nokia).
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