3.1 Introduction to Computer Software:

Computer software refers to a set of instructions or programs that tell the computer how to carry out specific tasks. It is the non-physical component of the computer system, in contrast to hardware (the physical parts like the CPU, memory, etc.).

Software is divided into two broad categories:

1. System Software: This is software that helps the computer run and provides a platform for running application software. The most common example is the Operating System (OS), like Windows, Linux, or macOS.
2. Application Software: These are programs designed for end-users to perform specific tasks. Examples include word processors (like Microsoft Word), web browsers (like Google Chrome), and multimedia players (like VLC).

3.2 Types of Software and Its Features:

1. System Software:

The software that manages controls and supports computer system is called system software. So, system software creates link between computer and user. It is a platform for running application software. It manages files and folders. It can be sub-divided into the operating system, utility software, device driver software, language processing software, etc, are example of system software

i)  Operating System (OS):

An operating system is the system software that manages and controls the overall operation of a computer. It coordinates, controls, and manages computer hardware. The operating system is installed in the C: drive of the hard disk. It is the first software that is loaded into computer memory (RAM). The popular operating system are Windows XP, Windows 7, Windows 8, Windows 10, Linux based fedora, UNIX, MS-DOS etc. Android Kit Kat, Android Marshmallow, Android Oreo are the popular operating system of Android Smartphone and IOS is the operating system of Apple iPhones

ii) Language Processor :. A computer program is a set of instructions to perform tasks. System software that converts different programming languages into machine-level language is called a language processor. So language processor converts high-level language or assembly language into machine-level language and vice versa.

The three types of language processors are explained below:

a)Assemblers: An assembler is a type of language processor that converts program code written in assembly language into machine language. Machine-level language uses binary digits, 0 or 1, to write a program, which is difficult. So a programmer writes programs using assembly language. Mnemonic Code is used for writing a program in assembly language.

b. Compilers

The high-level programming language is developed for the improvement of assembly. A compiler is a type of language processor that converts the program written in a high-level language into machine-level language at once. Example C, C#, C++, Java, PHP, etc. are compiler-based programming languages.

c) Interpreter: An Interpreter is a type of language processor that converts the program written in a high-level language into machine-level language line by line. If there is any error in the middle of the program, then the program is interrupted in between. So, after removing the error, the program needs to run again from the beginning. LOGO, QBASIC, BASICA, Perl, Python, etc. are interpreter-based languages

iii. Utility Software: Utility software is also called a service program. A set of programs that perform tasks related to the maintenance of computer software and hardware is called utility software. The main objective of utility software is the smooth functioning of the computer system. The examples of utility software are:

• Antivirus software (Kaspersky, Norton Antivirus)
• Backup Software (Nova BACKUP Professional, Ashampoo Backup Pro)
•  Encryption Tools (Versacrypt, Bitcocker)
• File Compression Tools (Winzip, WinRAR)
• Disk Utilities (Disk Defrag, WinDirstat)

2. Application Software:

Application software is designed to fulfil the requirement of user. A set of programs designed to do specific tasks is called application software. The application software is used to type e-mail, edit photos, prepare a presentation, listen to music, design engineering work, edit videos, produce bills etc. The popular two types of application software are given below.

i) Packaged/General Purpose Application Software The software developed for all general users to perform their generalized tasks is called general-purpose application software. It cannot be modified as per user’s requirement. It is costlier and easily available in the market. The examples of general-purpose application software are:

• MS Office Package (MS-Word, MS-Excel, MS-PowerPoint)
• Adobe Photoshop l Auto CAD
•  SPSS (Statistical Package for the Social Sciences)
• Autodesk Maya. MS Office Package (MS-Word, MS-Excel, MS-PowerPoint)
•  Adobe Photoshop l Auto CAD l SPSS (Statistical Package for the Social Sciences)
•  Autodesk Maya.
• spreadsheets.

3.3 Introduction to Operating System:

An Operating System (OS) is a special kind of software that enables users to interact with the computer hardware. It is the backbone of your computer and ensures everything runs smoothly. Without an OS, you would not be able to use applications, manage files, or even interact with the computer easily.

Key roles of an Operating System:

1. Managing Hardware: It controls and allocates hardware resources such as the CPU, memory, and storage to ensure efficient operation.
2. Providing User Interface: The OS provides a way for users to interact with the computer, such as through graphical icons, windows, and menus.
3. Running Programs: The OS enables users to run application programs and ensures that multiple programs can run simultaneously without conflict.
4. Security: It ensures that users are protected from unauthorized access by requiring passwords and managing user permissions.
5. File Management: It manages files and directories, making sure data is stored and retrieved efficiently from storage devices like hard drives or SSDs.

Examples of Operating Systems:

• Microsoft Windows: The most widely used OS for personal computers, known for its graphical interface.
• macOS: The operating system developed by Apple for its desktops and laptops.
• Linux: An open-source OS that is popular among developers, known for its flexibility and customization options.
• Android/iOS: These are mobile operating systems used on smartphones and tablets.

3.4 Functions and Characteristics of an Operating System:

1. Memory Management: The OS ensures that each application running on the computer has enough memory to function. It also manages the available memory by assigning it to different tasks and ensuring that programs don’t use more memory than they need.

2. Process Management: The OS handles running programs (processes) on the computer. It schedules tasks, allocates resources, and manages execution so that everything works smoothly, even when multiple tasks are running at the same time.

3. File Management: The OS organizes files on storage devices (like hard drives). It keeps track of where files are stored, allows users to create, delete, or move files, and ensures they are saved in an organized structure (folders).

4. Device Management: The OS communicates with hardware devices (such as printers, keyboards, or displays) and ensures they work properly. It handles input/output (I/O) operations between the hardware and software.

5. Security: The OS enforces security protocols, such as requiring passwords for login, protecting files from unauthorized access, and ensuring the system is protected from malware.

3.5 Types of Operating Systems:

1. Single-User Operating System: A single-user operating system allows only one person to use the computer at a time. It is simple, easy to operate, and commonly used in personal computers at homes and schools. This type of OS manages files, applications, and hardware for a single user efficiently. It does not allow multiple people to log in at the same time. Examples include Windows and macOS. It is best suited for daily activities like browsing, studying, and entertainment.

2. Multi-User Operating System: A multi-user operating system allows many users to use the computer at the same time through a network. It manages and shares system resources like storage, memory, and processing power among all users. This type of OS is mostly used in offices, banks, and large organizations where many people work together. It ensures that each user gets proper access without disturbing others’ work. Examples include UNIX and Linux servers. It makes group work and data sharing easier.

3. Real-Time Operating System (RTOS): A real-time operating system works very quickly and gives immediate responses. It is used in systems where timing is extremely important, such as robots, medical machines, traffic lights, and airplanes. RTOS handles tasks within a fixed time limit, which makes it reliable and accurate. It is designed to work continuously without errors. Examples include VxWorks and QNX. This type of OS is essential for machines that require fast and precise control.

4. Distributed Operating System A distributed operating system connects many computers together and makes them work like a single powerful system. It shares resources and information among all connected computers, which helps in completing large tasks faster. This type of OS is used in research centers, scientific labs, and big companies. It increases speed, efficiency, and data security. Distributed Linux systems are common examples. It makes complex computing easier by dividing the work among multiple machines

5. Single-Tasking Operating System: A single-tasking operating system can run only one program at a time. It is simple and does not require much memory or processing power. This type of OS was common in older computers and mobile devices. Because it can handle only one task, it becomes slow and inefficient for modern needs. Although it is easy to manage, it is not suitable for multitasking work. Early mobile operating systems are examples of single-tasking OS.

6. Multi-Tasking Operating System

A multi-tasking operating system can run many programs at the same time. It allows users to switch between tasks such as browsing, listening to music, and typing documents without closing any program. This type of OS manages processor time and memory to keep all tasks running smoothly. Modern computers, smartphones, and laptops mostly use multitasking operating systems. Examples include Windows, Android, and Linux. It increases productivity and makes the computer more useful.

3.6 User Interface:

The User Interface (UI) is the medium through which the user interacts with the computer. It helps the user to interact with both the system and applications. In another way, UI is the part of a computer system that allows users to interact with the device through visual elements like icons, buttons, menus, and windows.

1. CUI (Character User Interface):

A Character User Interface (CUI) is a type of interface where the user interacts with the computer by typing text or characters on the keyboard. It does not use images, icons, or buttons; instead, everything is done using typed commands. The computer displays the output in simple text form on the screen. CUIs are mostly used by programmers, technicians, or in older computer systems where only text-based communication is possible.

Also called Command Line Interface (CLI), it requires the user to type commands to perform tasks. It is less visual and relies on text-based commands to interact with the system. Example: Early versions of MS-DOS required users to type commands like dir to list files.

2. GUI (Graphical User Interface):

A Graphical User Interface (GUI) is a type of interface that allows users to interact with a computer using visual elements like icons, buttons, windows, and images. Instead of typing commands, users can simply click, drag, or tap on items to perform tasks. GUIs make computers easier to use because everything is displayed in a clear and attractive way. This type of interface is commonly found in modern devices such as computers, smartphones, and tablets.

Example of GUI: The  Windows operating system, where users click on icons, buttons, and menus to open programs and perform tasks.

3. Touch User Interface (TUI)

A Touch User Interface (TUI) is a type of interface where users interact with a device by touching the screen directly. Instead of using a mouse or keyboard, users can tap, swipe, drag, or pinch to control the device. This interface makes using devices fast and easy because actions happen through simple finger movements. TUIs are commonly found in smartphones, tablets, ATMs, and touch-screen computers.

3.7 OSS (Open Source Software):

Open Source Software (OSS) is software whose source code is freely available for anyone to see, use, modify, and share. This means programmers can study how the software works and improve it by adding new features or fixing problems. OSS promotes learning, collaboration, and innovation because it is open to everyone. Examples of open source software include Linux, Mozilla Firefox, and LibreOffice.

Advantages of OSS

1. Free or Low Cost: Most open source software is available for free, which means you don’t have to pay money to use it. Even if some OSS comes with a small fee for extra services, it is usually much cheaper than proprietary software. This makes it accessible to students, small businesses, and organizations with limited budgets

2. Customizable: Open source software allows users to modify the code according to their needs. For example, a company can add features that are specific to its work. Developers can change the appearance, functions, or behavior of the software to make it more useful. This flexibility is not possible in commercial software because its source code is hidden.

3. Secure and Reliable: Open source software is generally more secure because its code is open for everyone to check. Many developers from around the world review it to find and fix bugs or vulnerabilities. If a security problem appears, it can be solved quickly by the community. OSS tends to be reliable because it is constantly tested and improved by a large number of users. Companies and organizations trust OSS for important tasks because it has fewer hidden threats.