Unit 1 Introduction to operating System (CLASS 11)

Introduce Operating System

An Operating System (OS) is system software that acts as an interface between the computer hardware and the user. It manages computer resources and provides services for programs to run efficiently.

Examples of popular operating systems include:

• Microsoft Windows
• Linux
• macOS
• Android
• iOS

 Function of OS

1. Process Management

The operating system helps in running many programs at the same time. It keeps track of each running program (called a process), decides which one should run next, and stops or starts them as needed. It makes sure that all the programs get a fair chance to use the CPU.

 

2. Memory Management

The OS manages the computer's memory (RAM). It decides which program will use how much memory and keeps track of it. When a program is closed, it frees up the memory so that other programs can use it. This helps the computer run smoothly without crashing.

 

3. File System Management

The operating system helps us to create, save, open, and delete files. It organizes files in folders and keeps them safe. It also controls who can open or edit a file to protect our data.

 

4. Device Management

The OS controls all the input and output devices like the keyboard, mouse, printer, and monitor. It tells the devices what to do and makes sure they work properly. It also uses special programs called drivers to communicate with the devices.

 

5. User Interface

The operating system provides a way for us to use the computer. It can be a text-based interface (like typing commands) or a graphical interface (with icons and windows). This makes it easier for users to give instructions and control the computer.

 

6. Security and Protection

The OS keeps the computer safe from unwanted access. It allows only authorized users to log in and use the computer. It also protects files and programs from viruses or other harmful programs.

 

7. Job Scheduling

When many tasks need to be done, the OS decides which one to do first. It plans and schedules the work so that all tasks are completed in a good order without wasting time or resources.

 

8. Error Detection and Handling

The operating system checks if there are any problems in the computer, like hardware failures or program errors. If it finds any, it tries to fix them or shows a message so the user can take action.

 

9. Networking

The OS helps the computer connect to other computers through the internet or a local network. It allows sharing of files, printers, and other resources easily between computers.

 

10. Resource Allocation

The operating system gives hardware resources like CPU time, memory, or devices to different programs as needed. It makes sure all programs get what they need and that nothing is wasted.

 Types of Operating System (Based on Processing Method)

1. Batch Operating System

A Batch Operating System processes a group of similar jobs together without requiring user interaction during

execution. Jobs are collected, arranged in batches, and executed one after another automatically. This type of

operating system is commonly used for large-scale data processing tasks such as payroll and billing systems.

2. Time-Sharing Operating System

A Time-Sharing Operating System allows multiple users to access the computer system simultaneously by

allocating a small portion of CPU time to each user. This creates the illusion that all users are working at the

same time. It provides quick response times and efficient utilization of system resources.

3. Multiprocessing Operating System

A Multiprocessing Operating System uses two or more processors to perform multiple tasks simultaneously.

The workload is distributed among processors, resulting in faster execution and improved system performance.

It is widely used in high-performance computing environments.

4. Multitasking Operating System

A Multitasking Operating System enables a user to run multiple programs at the same time. The operating system

rapidly switches the CPU between tasks, allowing applications to execute concurrently. This improves

productivity and makes efficient use of system resources.

5. Real-Time Operating System (RTOS)

A Real-Time Operating System is designed to process data and respond to events within a specified time limit. It

is used in situations where timely responses are critical, such as medical equipment, robotics, and air traffic

control systems. RTOS ensures reliability and predictable performance.

6. Distributed Operating System

A Distributed Operating System manages multiple interconnected computers and makes them function as a single

system. It allows users to share resources, data, and processing power across different machines. This type of

operating system improves performance, scalability, and reliability.

Operating System Based on User Interface

1. Command User Interface (CUI)

A Command User Interface (CUI) allows users to interact with the computer by typing commands through a

keyboard. Users must remember specific commands to perform tasks. CUI is fast and efficient for experienced

users but can be difficult for beginners.

2. Graphical User Interface (GUI)

A Graphical User Interface (GUI) enables users to interact with the computer using graphical elements such as

windows, icons, menus, and pointers. It is user-friendly, easy to learn, and widely used in modern operating

systems such as Windows and macOS.

Operating System Based on Mode of Use

1. Single-User Operating System

A Single-User Operating System allows only one user to access and operate the computer system at a time. It is

commonly used in personal computers and is designed to manage resources for a single user's tasks and

applications.

2. Multiuser Operating System

A Multiuser Operating System allows multiple users to access the same computer system simultaneously. It

manages resources efficiently among users while maintaining security and separate user accounts. This type of

operating system is commonly used in servers and large organizations.

History and Development of Operating System

1. No Operating System (1940–1955)

• Early computers had no operating system.
• Programs were loaded and executed manually.
• Only one program ran at a time.

2. Batch Operating System (1955–1965)

• Similar jobs were grouped into batches.
• Jobs were executed automatically without user interaction.
• Improved CPU utilization.

3. Multiprogramming Operating System (1965–1975)

• Multiple programs were kept in memory at the same time.
• The CPU switched between programs to increase efficiency.

4. Time-Sharing Operating System (1970s)

• Multiple users could use the computer simultaneously.
• Each user received a small share of CPU time.
• Provided interactive computing.

5. Modern Operating System (1980–Present)

• GUI-based and user-friendly.
• Supports multitasking, networking, security, cloud computing, and mobile devices.
• Examples: Windows, macOS, Linux, Android, and iOS.