📚 Computer Software and Operating System
Grade 11 Computer Science
Computer Software and Operating System -Complete Study Notes
Software
Software is a collection of related programs and associated documents that instruct the computer to perform specific tasks. It acts as a bridge between the user and hardware. Without software, hardware cannot perform any useful function, and software cannot run without hardware; they are mutually dependent.
Classification of Software
1. System Software
a. System Management
i. Operating System (OS)
ii. Utility software
iii. Device Driver
b. System Development
i. Programming Language
ii. Language Translator
c. Application Software
i. Packaged Software
Example: Facebook, TikTok
ii. Customized / Tailored Software
Examples: Payroll, Billing, School Management
Key Definitions
System Software
A set of one or more programs designed to control and manage the overall operation of the computer system. It does not fulfill specific user requirements; instead, it supports the running of other software and hardware. Examples: Windows, Linux, and macOS.
Operating System (OS)
A collection of programs that controls the overall operation of the computer. It is the first program loaded into memory when the computer starts. It provides a platform for application programs and an interface for the user. Examples: Linux, Windows, Mac.
Utility Software: Supporting software is used to perform specific maintenance tasks on the computer system. Also called service programs. Some are included in the OS; others are sold separately. Example Norton Utility, PC Tools, WinZip.
Device Driver: Software is responsible for the smooth functioning of a hardware device connected to the computer. When a new device is added, the corresponding device driver must be installed to allow the OS and device to communicate.
Programming Language: The language used to give instructions to a computer. Consists of keywords, variables, operators, loops, and Symbols. Two types: Low-level language (Machine/assembly) and High-Level Language (C, Python, Java, PHP, C#)
Language Translator: Special software that translates programs from one language to another is also called a language processor. Three types: Compiler (translates entire program at once), Interpreted (line by line), and Assembler (translates assembly to machine code).
Application Software: A set of programs designed to perform a specific task for the user. Developed using high-level languages. Fulfills user demands like preparing bills, mark sheets, and calculations. Examples: MS-Excel, Photoshop, Billing Software.
Packaged Software: Generalized, large-sized, error-free, and advanced software developed by reputed companies for general purposes. Expensive for small organizations and cannot be easily modified. Examples: MS-Office, Adobe, Macromedia.
Customized/ Tailored Software: Software is developed for a specific user or organization to solve a specific problem. Written in high-level language by local programmers. Can be easily modified. Examples: Payroll system, Inventory management, School Management.
Functions / Features of OS (V. Imp)
a. I/O Management: Manages interaction with peripheral devices like keyboard, mouse, printer, scanner, and controls all input and output operations.
b. User Interface (UI): Provides an ideal environment for users to interact with the computer. Two types: CUI (MS-DOS) and GUI (Windows, macOS)
c. Security: Protects against viruses, unauthorized access, and suspicious network activity using built-in tools, passwords, and user access control.
d. Process Management: Allocates the processor to execute chosen processes. Acts as a traffic controller, job scheduler, process scheduler, and dispatcher.
e. Memory Management: Determines the memory needed, allocates RAM for programs and data, and frees memory when a program terminates to load new ones.
f. Data Management: Organized data into logical groupings called files. Modern OS provides flexible file management; older OS lacked this feature.
g. Command Interpreter: Reads user commands typed at a terminal, interprets them, and translates them into detailed instructions the hardware can execute.
h. Deadlock Prevention: Prevents situations where two processes hold resources needed by each other, causing neither to execute. The OS carefully allocates resources to avoid this.
i. Time Sharing: Allocates CPU time among multiple users on the same computer simultaneously. Common in network OS like Windows NT.
j. Virtual Memory: Compensates for the shortage of physical RAM by using disk space temporarily. A virtual address is mapped to a real address through a process called mapping/ swapping.
Types of operating systems based on different categories.
| Basis of Processing | Basis of User Interface | Basis of the Mode of User
| Multi-Programming OS | Character UI (CUI) | Single User
| Multi-tasking OS | Graphical UI (GUI) | Multi User
| Multi-processing OS | - | -
| Time-Sharing OS | - | -
| Batch Processing OS | - | -
| Multi-threading OS | - | -
| Real-time OS | - | -
| Online Processing OS | - | -
On the basis of processing
1. Multi-programming OS: A technique where multiple programs are loaded into memory simultaneously and executed by a single processor. When one program is being processed, another is waiting, giving an impression of simultaneous execution. The main purpose of a multi-programming OS is to increase CPU utilization. Different forms include multi-tasking, multi-programming, and multi-user.
2. Multi-Tasking: Allows more than one program to run concurrently, mainly in a single-user system. One process may be foreground (active) and others background (inactive). Increases user productivity. Examples: MS Windows, Linux, macOS.
3. Multi-processing OS: Has more than one processor (CPU) linked in a coordinated way. Each processor runs a portion of the program simultaneously, also known as parallel processing. More costly and complex than multi-programming, but it dramatically increases speed. Example: UNIX
4. Time-Sharing OS: Enables many users at different terminals to use one computer at the same time. CPU switches between users so frequently that each user receives an immediate response. Advantages: Quick response, reduced CPU idle time, whereas Disadvantages: Reliability issues, less security.
5. Batch Processing OS: Groups Similar jobs (programs, data, commands) and processes them together, also called offline processing. User submits jobs and collects results later. Suitable for Payroll, weather forecasting, and statistical analysis. Major disadvantage: no interaction between the user and the program during execution.
6. Multi-threading OS: Divides a process into multiple threads (sub-processes) and executes them concurrently. Threads are lightweight processes. Minimized the burden of context switching and improved efficiency.
7. Real-time OS: Controls the environment by receiving data and responding instantly. Processing must be completed within a predefined time (time-critical). Used in airline seat booking, Rocket launching systems, and wholesale supplier management.
8. Online processing OS: Transactions are processed immediately as they happen at the point of origin. Output is returned immediately after processing.
Important components of GUI (V. Imp)
· Icon: Small picture representing commands, files, or windows.
· Pointer: Arrow symbol controlled by mouse/trackpad.
· Desktop: Area on screen where icons are grouped.
· Windows: Resizable on-screen areas running different programs.
· Menus: Lists of commands to choose from.
· Folders: Graphical representation of a directory.
Important Operating System
a. UNIX: Powerful, flexible OS, Multi-user, multi-tasking, multi-processing. Used in mainframe & minicomputers. Developed by AT & t Bell Labs in 1970, which was written in C and Assembly, which is the parent of Linux and Solaris.
b. LINUX: Open-source, Unix-based OS. Developed by Linus Torvalds at the University of Helsinki. Multi-user, multi-tasking, multi-programming. Linux is popular for servers, and Distros are Red Hat, Ubuntu, Fedora, and Debian.
c. macOS: Popular GUI-Based OS by Apple for Macintosh Computers. High-quality graphical interface. Originally for Motorola 68000 processors, now compatible with Intel processors.
d. Open-Source OS: Source code freely available under the General Public License. Can be modified and redistributed. Free of cost. Example Linux, Unix, Minix, Apache.
Mobile Computing
Mobile Computing is a technology that allows users to access, transmit, and receive data from anywhere using portable wireless devices without being connected to a fixed physical link. It enables computing tasks to be performed while the user is on the move, using devices like smartphones, tablets, laptops, and PDAs connected via wireless networks (WI-FI, Bluetooth, 4G/5G).
Three Core Elements of Mobile Computing
a. Mobile Hardware: Portable devices used in mobile computing, smartphones, tablets, laptops, PDAs, and smartwatches. These devices have built-in wireless communication capability.
b. Mobile Software: Application programs (apps) that run on mobile hardware, mobile OS (Android, IOS), and applications like maps, email, and banking apps.
c. Mobile Communication: The infrastructure and protocols used for wireless communication, Wi-Fi, Bluetooth, 3G, 4G, 5G, NFC.
Important Questions
1. What is software? What are its types? Explain with examples.
Ans: Software is a collection of related programs and associated documents that instruct the computer hardware to perform specific tasks. Hardware alone cannot function without software, and software cannot run without hardware; they are interdependent.
Software is mainly classified into two types:
a. System Software: Programs designed to control and manage the operation of the computer. Examples: Windows, Linux. It is future divided into System Management (OS, Utility, Device Driver) and System Development (Programming Language, Language Translator).
b. Application Software: Programs designed to fulfill specific user requirements. Examples: MS-Excel, Photoshop. It is divided into Packaged Software (MS-Office) and Customized Software (School Management System).
1. What is a language translator? Explain its types.
Ans: A language translator (also called a language processor) is specialized software that translates programs written in one language into another language that the computer can understand.
Types of Language Translators:
a. Compiler: Translates the entire program at once from high-level to machine language. Example: C, C++ compiler.
b. Interpreter: Translates and executes the program line by line. Example: Python interpreter.
c. Assembler: Translate assembly language (low-level) into machine language (binary).
2. What is an Operating System? Write its functions.
Ans: An operating system (OS) is a collection of programs that controls the overall operation of the computer system. It is the first program loaded into memory when the computer is turned on.
Functions of the Operating System
a. Provides a platform for other application programs to run.
b. Provides a user interface so users can communicate with the computer.
c. Manages memory, CPU, and hardware resources.
d. Handles file management (Creating, deleting, reading files).
e. Controls input/ Output operations.
Examples of Operating Systems are Linux, Windows, and macOS
1. What is a deadlock? How does OS prevent it?
Ans: Deadlock is a situation in which two or more processes cannot continue because each holds a resource needed by the other. Neither process can execute, causing the system to hang. E.g., Process A holds Resource A and needs Resource B. Process B needs Resource B and Resource A. Neither can proceed, and the situation is called a deadlock.
To prevent the deadlock, the OS will allocate resources and take situational action, ensuring no circular dependency exists between processes.
2. What is virtual memory? Explain mapping and swapping.
Ans: Virtual memory is a technique used by the OS to execute large programs when available primary memory (RAM) is insufficient. It uses free space in secondary memory (disk) as an extension of RAM. It is not actual memory; it is a management technique.
In virtual memory, large programs are divided into small segments called pages.
Mapping
The process of translating virtual addresses into real (physical) addresses in RAM.
Swapping
The process of copying virtual pages from disk to main memory when they are needed for execution.
3. What is batch processing? Write its advantages and disadvantages.
Ans: Batch Processing is a technique of grouping similar jobs (programs, data, system commands) and processing them as a group, also called offline processing. Users submit jobs to the operator and collect the results later. Jobs are stored in a queue on disk and executed one after another.
The advantages of batch processing is user need not wait during processing, and it is suitable for large-scale tasks like payroll, weather forecasting, and statistical analysis.
The main disadvantage of batch processing is that there is no interaction between the user and the program during execution.
4. What is spooling? Why is it used?
Ans: Spooling stands for Simultaneous Peripheral Operation online. It is a process used to balance the speed difference between the high-speed CPU and slow I/O devices.
It is primarily used for printing. When multiple files are sent to the printer, they are lined up in a queue and printed one by one. Meanwhile, the CPU remains free, and the user can continue working on other applications. The technique is made possible by the OS’s spooling capacity.
5. What is Mobile Computing? Explain its advantages and disadvantages.
Ans: Mobile Computing is a technology that allows users to access, transmit, and receive data from any location using portable wireless devices without a fixed physical connection. Devices used include smartphones, tablets, laptops, and PDAs, connected via Wi-Fi, 3G, 4G, 5G, or Bluetooth.
The advantages of mobile computing are: -
· Location flexibility, users can work from anywhere
· Increased productivity for employees and businesses
· Instant communication through calls, email, and video conferencing
· Real-time access to information and databases
· Enables e-commerce, digital payments, and online banking
The Disadvantages of mobile computing are: -
· Security risks, vulnerable to hacking and data theft
· Dependent on the network, poor connectivity in remote areas
· Limited battery life affects uninterrupted use
· Health hazards from prolonged screen use
· Can cause distraction and reduce productivity
6. What are the five applications of mobile computing?
Ans: The applications of mobile computing are: -
a. Education
b. Healthcare
c. Banking
d. Navigation
e. Emergency
f. E-commerce
7. Why is security a major concern in mobile computing?
Ans: Security is a major concern in mobile computing because mobile devices are used in various public and private environments, often connected to public Wi-Fi networks that are not secure.
The security risk that may arise in mobile computing is: -
a. Hacking and unauthorized access to personal and business data.
b. Malware, viruses, and spyware are installed through malicious apps.
c. Data interception on unsecured public Wi-Fi networks.
d. Device theft or loss leads to sensitive data exposure.
e. Phishing attacks through fake apps, emails, or messages.
User must use strong passwords, enable encryption, update software regularly, and avoid using sensitive apps on public networks to minimize security risks.
Summary of the chapter
Software is the bridge between user and hardware, classified into System Software (OS, Utility, Device Driver, Language Translator) and Application Software (Packaged and Customized). Neither hardware nor software can function alone.
The OS is the first program loaded on boot and performs 10 key functions: I/O management, UI, security, process management, memory management, data management, command interpretation, deadlock prevention, time sharing, and virtual memory (mapping + swapping).
Types of OS by processing: Multi-programming, Multi-tasking, Multi-processing, Time-Sharing, Batch, Multi-threading, Real-time, and Online. CUI = command-based, fast, technical; GUI = icon-based, user-friendly, multimedia support.
Mobile Computing enables wireless data access anywhere via hardware, software, and communication (3G/4G/5G/Wi-Fi). Key concerns: security (hacking, phishing, data theft). Applications: education, healthcare, banking, navigation, emergencies, e-commerce.