Introduction to Operating System

Unit 1 Syllabus

1. Introduction to Operating System

An Operating System is system software that works as an interface between the user and the computer hardware. It manages all important resources of a computer such as CPU, memory, input-output devices, files and running programs.

Simple Example

When you open a browser, play music, save a file or print a document, the operating system manages these tasks. Without an operating system, a user cannot easily interact with computer hardware.

2. Evolution of Operating System

Operating systems developed gradually with computer hardware. In early computers, users had to directly operate machines using switches and punch cards. Later, operating systems became more advanced and user-friendly.

• Serial Processing: No operating system was used. One job was executed at a time.
• Batch Processing: Similar jobs were collected and executed together.
• Multiprogramming: Multiple programs were kept in memory to improve CPU utilization.
• Time Sharing: CPU time was divided among multiple users.
• Modern OS: Supports GUI, networking, security, multitasking and distributed processing.

3. Types of Operating Systems

1. Batch Operating System

In batch OS, similar jobs are grouped together and executed without user interaction.

2. Time Sharing Operating System

In time sharing OS, CPU time is shared among multiple users or processes. It gives quick response to users.

3. Multiprogramming Operating System

In multiprogramming, multiple programs are loaded into memory at the same time so that CPU does not remain idle.

4. Multiprocessing Operating System

Multiprocessing OS uses more than one processor to execute processes faster.

5. Distributed Operating System

Distributed OS manages a group of independent computers and makes them appear as a single system to users.

6. Real Time Operating System

Real time OS gives output within a fixed time limit. It is used in medical systems, aircraft control and industrial systems.

4. Operating System Services

Operating system provides many services to users and application programs.

• Program Execution: Loads and runs user programs.
• I/O Operations: Controls input and output devices.
• File System Management: Creates, deletes, reads and writes files.
• Communication: Allows processes to communicate with each other.
• Error Detection: Detects hardware and software errors.
• Resource Allocation: Allocates CPU, memory and devices.
• Protection and Security: Protects system from unauthorized access.

5. System Calls

System calls provide an interface between user programs and the operating system. When a program needs any service from the OS, it uses a system call.

Types of System Calls

• Process Control: create process, terminate process, wait, execute.
• File Management: create file, open file, read file, write file, delete file.
• Device Management: request device, release device, read, write.
• Information Maintenance: get time, set time, get system data.
• Communication: send message, receive message, create connection.

6. Operating System Structure

OS structure defines how different parts of an operating system are organized and connected.

7. System Boot

System boot is the process of starting a computer and loading the operating system into main memory.

Steps of Booting

• Power is supplied to the computer.
• BIOS or firmware starts execution.
• Hardware checking is performed.
• Bootloader is loaded from storage device.
• Operating system kernel is loaded into memory.
• System becomes ready for user interaction.

8. Spooling and Buffering

Spooling

Spooling stands for Simultaneous Peripheral Operations Online. It stores data temporarily in a queue so that slow devices like printers can process it one by one.

Buffering

Buffering means temporarily storing data in memory while it is being transferred between two devices or processes. It helps to handle speed differences between sender and receiver.

Important Exam Questions

• Define Operating System. Explain its functions.
• Explain evolution of Operating System.
• Explain different types of Operating Systems.
• What are Operating System services?
• Explain system calls and their types.
• Explain Operating System structure.
• Explain booting process.
• Differentiate between spooling and buffering.

Short Viva Questions

• What is an Operating System?
• What is kernel?
• What is system call?
• What is booting?
• What is spooling?
• What is buffering?
• Give two examples of operating systems.