INTODUCTION TO OPERATING SYSTEM

  INTRODUCTION TO OPERATING SYSTEMS

 INTRODUCTION

An operating system (OS) is system software that manages computer hardware and software resources and provides common services for computer programs. The operating system is a vital part of the system software in a computer system; operating systems are an essential part of modern computing. They provide the foundation for all other software, and they make it possible for us to use our computers in a productive and efficient way.

A computer system consists of hardware, system programs, and application programs. Operating system is an interface between user and Hardware, concepts are fundamental principles that fortify the design, functionality, and management of operating systems (OS). These concepts provide a framework for understanding how an operating system works and how it interacts with hardware, software, and users.

Key Operating System Concepts:

Process Management: The OS manages processes, which are executing instances of a program. It allocates CPU time, memory, and other resources to processes, schedules their execution, and provides mechanisms for inter-process communication and synchronization.

 Memory Management: This concept deals with the allocation and management of computer memory. The OS is responsible for ensuring that each process has enough memory to execute without interfering with other processes, and it uses techniques like virtual memory to efficiently manage memory space. File Systems: File systems provide a structured way of organizing and storing data on storage devices such as hard drives. The OS manages file operations like reading, writing, and deleting files and ensures data integrity and security. 

Device Management: The OS handles interactions with hardware devices such as printers, keyboards, and disks. It provides device drivers to communicate with hardware and manages input/output (I/O) operations.

 CPU Scheduling: As multiple processes compete for CPU time, the OS implements scheduling algorithms to determine which process gets access to the CPU and when. Efficient scheduling improves overall system performance and responsiveness.

 Inter-Process Communication (IPC): Operating systems facilitate communication and data sharing between processes using various IPC mechanisms like shared memory, message passing, and semaphores.

 Security and Protection: OS concepts include mechanisms to protect system resources and data from unauthorized access, ensuring the security and integrity of the system. 

Virtualization: This concept allows multiple virtual machines or containers to run on the same physical hardware, enabling better resource utilization and isolation between applications.

•  Distributed Systems: Operating systems for distributed environments manage multiple interconnected computers, providing transparent access to resources across the network.                                           System Calls: These are interfaces that allow user-level applications to request services from the operating system, such as opening files, creating processes, and allocating memory. Understanding these operating system concepts is essential for developers, system administrators, and anyone working with computers, as it forms the foundation for efficiently using, managing, and troubleshooting operating systems. 

The Operating System as a Resource Manager :

An operating system (OS) is a software program that manages computer hardware and software resources and provides common services for computer programs. One of the most important tasks of an OS is resource management. 

Resources in a computer system can be divided into two main categories: 

 Hardware resources: These include the CPU, memory, storage devices, and input/output (I/O) devices. 

 Software resources: These include files, processes, and threads. The OS is responsible for managing these resources in a way that ensures that they are used efficiently and fairly. 

This includes: 

 Allocating resources to programs as needed. 

 Ensuring that no one program uses too many resources. 

 Preventing programs from interfering with each other. 

 Recovering resources that are no longer being used. The OS uses a variety of techniques to manage resources, such as: 

 Scheduling: The OS schedules the execution of programs so that they all get a fair share of the CPU time. 

 Memory management: The OS manages the memory in the computer system so that it is used efficiently.

  File management: The OS manages the files in the computer system so that they can be accessed and used by programs

 Process management: The OS manages the processes in the computer system so that they can run concurrently and without interfering with each other. Resource management is a complex task, but it is essential for the smooth operation of a computer system. The OS plays a vital role in resource management, and it is responsible for ensuring that resources are used efficiently and fairly. 

COMMON TYPES OF OPERATING SYSTEMS:

 Single-User Operating System: A single-user operating system is designed to support only one user at a time. It is commonly used on personal computers and workstations where a single user interacts with the system at any given time. 

 Multi-User Operating System: A multi-user operating system allows multiple users to access and use the system simultaneously. Each user has their own account and can run their processes independently.  Batch Processing Operating System: Batch processing operating systems execute tasks in batches without direct user intervention. Users submit jobs as batches, and the system processes them in sequence without requiring real-time interaction. 

 Real-Time Operating System (RTOS): RTOS is designed to meet strict timing constraints and provide predictable response times for real-time applications. It is commonly used in embedded systems, industrial automation, and control systems. 

 Time-Sharing Operating System (Multi-tasking OS): Timesharing operating systems enable multiple users or processes to share the CPU's time simultaneously. The CPU switches rapidly between tasks, giving the illusion of concurrent execution. 

 Distributed Operating System: A distributed operating system runs on a network of interconnected computers and allows them to work together as a single system. Distributed OS provides transparency to users and applications, making the network appear as a single resource.

 Network Operating System (NOS): A network operating system is specifically designed for managing and coordinating network resources and services. It facilitates file sharing, printer sharing, and centralized user administration in a networked environment. 

 Mobile Operating System: Mobile operating systems are designed for smartphones, tablets, and other mobile devices. They are optimized for touch-based input and mobile-specific hardware features. 

 Standalone Operating System: A standalone operating system is designed to work independently on a single computer or device without relying on network resources or connections. 

 Embedded Operating System: Embedded operating systems are tailored for use in embedded systems with limited resources. They often run on specialized hardware and focus on specific tasks or functions.

   Virtualization Operating System: Virtualization OS runs on virtual machines and enables multiple virtualized operating systems to run on a single physical machine, allowing efficient resource utilization and isolation between applications.

  Hybrid Operating System: A hybrid operating system combines the characteristics of multiple types of operating systems. For example, modern desktop operating systems often have elements of single-user, multi-user, and time-sharing systems. 

The type of operating system used depends on the intended use case, hardware platform, and specific requirements of the applications and users. Different types of operating systems serve various purposes and cater to diverse computing environments. 

The Operating system is responsible for: 

 Hardware management: The operating system manages the computer's hardware resources, such as the CPU, memory, and storage devices. It allocates these resources to programs as needed, and ensures that they are used efficiently. 

 Software management: The operating system manages software resources, such as files and processes. It provides a way for programs to access files and other resources, and it ensures that programs do not interfere with each other.

  User interface: The operating system provides a user interface (UI) that allows users to interact with the computer. The UI can be graphical (GUI) or text-based (TUI).

  Device drivers: The operating system provides device drivers for hardware devices, such as printers, scanners, and network cards. Device drivers allow programs to access these devices. There are many different types of operating systems, each with its own strengths and weaknesses. Some of the most popular operating systems include: 

 Windows: Windows is the most popular operating system in the world. It is a graphical operating system that is used by millions of people on personal computers, laptops, and tablets.  macOS: macOS is the operating system for Apple's Macintosh computers. It is a graphical operating system that is known for its user-friendliness and stability. 

 Linux: Linux is a free and open-source operating system that is used by millions of people around the world. It is a powerful operating system that is used for both personal computers and servers. 

  Android: Android is a mobile operating system that is used by billions of people on smartphones and tablets. It is a powerful and flexible operating system that is known for its customization options. 

    OPERATING SYSTEM STRUCTURE The structure of an operating system refers to its organization and the way its components are designed and interact with each other. Operating systems typically follow a layered or modular architecture to provide abstraction, flexibility, and ease of maintenance. The key components of an operating system structure include:

               KERNEL: The kernel is the core component of the operating system, residing in privileged mode, directly interacting with hardware, and providing essential services to user programs. It manages system resources, such as memory, CPU, and devices, and enforces security and protection mechanisms. The kernel is responsible for process management, memory management, device drivers, and I/O operations.     

KERNEL: The kernel is a critical component of an operating system that serves as the core or central part of the software. It operates in privileged mode with direct access to hardware and provides essential services and functionalities for the rest of the operating system and user-level applications. The kernel is responsible for managing system resources, ensuring security and protection, and providing an interface for user programs to interact with the underlying hardware. Here are some key aspects of the kernel

 Core Functions: 

 Process Management: The kernel manages processes, including their creation, scheduling, termination, and context switching.

  Memory Management: It allocates and de-allocates memory for processes and handles memory protection and virtual memory. 

 Device Management: The kernel communicates with hardware devices through device drivers to facilitate I/O operations. 

 File System Management: It handles file operations and provides an interface for user programs to access and manage files on storage devices

Privileged Mode: The kernel operates in privileged mode (also known as supervisor or kernel mode), which allows it to execute privileged instructions and access hardware resources directly. User programs run in user mode, which restricts them from performing privileged operations directly.  System Calls: The kernel provides an interface called system calls through which user-level applications can request services and functionalities from the kernel. When a user program needs to perform a privileged operation (e.g., reading from a file, creating a new process), it makes a system call to the kernel, which then handles the request on its behalf.                                                                           Interrupt Handling: The kernel manages interrupts generated by hardware devices, such as keyboard input, disk I/O, and network communication. When an interrupt occurs, the kernel interrupts the current execution of a program, handles the interrupt, and resumes the program.                                        Process Synchronization and Protection: The kernel ensures that processes are properly synchronized when accessing shared resources to avoid conflicts and data corruption. It enforces protection mechanisms to prevent unauthorized access to system resources and ensure the security of the system.

  Types of Kernels 

Monolithic Kernel: - In a monolithic kernel, the kernel and operating system, both run in the same memory, and it is mainly used where security is not a major concern. The result of the monolithic kernel is fastly accessible. But in some situations, like if a device driver has a bug, then there may be chances of a whole system crash. 

Microkernel: - A Microkernel is the derived version of the monolithic kernel. In microkernel, the kernel itself can do different jobs, and there is no requirement of an additional GUI. 

Hybrid kernel: - Hybrid kernel is a mixture of microkernel and monolithic kernel. The Hybrid kernel is mostly used in Windows, Apple’s macOS. Hybrid kernel moves out the driver and keeps the services of a system inside the kernel. 

System Calls in OS:                                                                                                                                                             System calls are an essential interface provided by the operating system that allows user-level applications to request services and access functionalities that are only available in privileged mode (kernel mode). They act as a bridge between user-space applications and the kernel, enabling user programs to interact with the underlying hardware and perform privileged operations. When a user program needs to perform a specific task that requires kernel-level privileges, it makes a system call to request the kernel to perform that task on its behalf. 

Here's how the process of a system call typically works:

User Program Initiates a System Call: A user-level application running in user mode requires certain services from the operating system, such as opening a file, creating a new process, or allocating memory. Since these operations need privileged access to hardware and resources, the user program cannot perform them directly.

 Entering Kernel Mode: To make a system call, the user program must transition from user mode to kernel mode, where the operating system's kernel resides. This transition is typically done through a special instruction or software interrupt provided by the processor. 

System Call Number and Arguments: The user program specifies the desired system call by providing a system call number or identifier. Additionally, any necessary arguments or parameters for the system call are passed to the kernel. These arguments convey the necessary information for the requested operation. 

Kernel Service Routine: The kernel maintains a table of system calls, each associated with a unique identifier or number. When the user program initiates a system call, the kernel looks up the corresponding entry in the system call table based on the system call number provided.

 Execution of System Call: Once the kernel has identified the appropriate system call and its arguments, it executes the corresponding kernel service routine that implements the requested functionality.

 Kernel Processing and Return: The kernel performs the privileged operation on behalf of the user program, using its unrestricted access to hardware and resources. After the system call is completed, the kernel returns the result or status of the operation to the user program. 

Returning to User Mode: Once the system call is finished, the user program transitions back to user mode, and normal execution of the program resumes.

 Examples of common system calls include: 

File-related system calls: open(), read(), write(), close() 

Process-related system calls: fork(), exec(), wait(), exit() 

Memory-related system calls: malloc(), mmap(), munmap() 

Network-related system calls: socket(), bind(), send(), recv() 

 System calls are essential for providing a secure and controlled environment for user programs to interact with the operating system and hardware, ensuring that sensitive operations are performed under the supervision and control of the kernel

 Device Drivers in OS: Device drivers are software components that allow the operating system to communicate with hardware devices, such as printers, disks, and network cards. Each device driver is specific to a particular hardware device and provides an abstraction layer for the kernel to access and control the device. Device drivers are software components that facilitate communication between the operating system and hardware devices. They serve as intermediaries, enabling the operating system to interact with various peripherals, such as printers, keyboards, graphics cards, network adapters, storage devices, and more. Device drivers are crucial for the proper functioning of hardware devices within a computer system. Here are the key aspects of device drivers: 

Purpose of Device Drivers: Hardware devices have their unique interfaces and communication protocols. The operating system, which is a general-purpose software, needs device drivers to understand and interact with these devices correctly. Device drivers provide an abstraction layer, shielding the operating system and user-level applications from the complexities of interacting directly with hardware. 

Functions of Device Drivers: Device Initialization: Device drivers are responsible for initializing the hardware devices during system startup or when the device is first detected.                                                     Device Configuration: They configure the device settings and parameters to ensure it operates efficiently within the system.                                                                                                                                Data Transfer: Device drivers manage the transfer of data between the operating system's memory and the hardware device. For example, they handle read and write operations to storage devices or network communication.                                                                                                                    Interrupt Handling: Device drivers manage hardware interrupts generated by devices to notify the CPU of specific events or data availability.                                                                                                    Error Handling: They handle errors that may occur during device operation and report them to the operating system or user-level applications.                                                                                                                    Overall, device drivers play a vital role in enabling the seamless interaction between operating systems and the diverse range of hardware devices used in modern computer systems. 

PRACTISE QUESTIONS ON THE ABOVE :

Question 1: What is the primary function of the kernel in an operating system?

A) Managing user interfaces

B) Allocating storage space

C) Managing hardware resources

D) Running applications

Answer: C) Managing hardware resources

Question 2: In a monolithic kernel architecture, where are all operating system services typically executed?

A) In separate user-level processes

B) In a single address space

C) In a microkernel

D) In a distributed fashion

Answer: B) In a single address space

Question 3: Which type of kernel architecture promotes modularity by keeping the kernel's functionality minimal?

A) Monolithic Kernel

B) Microkernel

C) Hybrid Kernel

D) Real-Time Kernel

Answer: B) Microkernel

Question 4: What is a characteristic of a single-user, single-tasking operating system?

A) Supports multiple users simultaneously

B) Executes one task at a time

C) Allows for real-time processing

D) Facilitates multi-threading

Answer: B) Executes one task at a time

Question 5: Which type of operating system allows a single user to run multiple applications simultaneously?

A) Single-User, Single-Tasking

B) Single-User, Multi-Tasking

C) Multi-User

D) Real-Time Operating System

Answer: B) Single-User, Multi-Tasking

Question 6: What is the primary distinction between a single-user and a multi-user operating system?

A) Number of installed applications

B) Concurrent access by users

C) Type of user interface

D) File storage capacity

Answer: B) Concurrent access by users

Question 7: In which application domain are Real-Time Operating Systems (RTOS) commonly used?

A) Office productivity

B) Gaming

C) Embedded systems and control systems

D) Web browsing

Answer: C) Embedded systems and control systems

Question 8: What does a distributed operating system facilitate?

A) Running multiple tasks on a single machine

B) Efficient memory management

C) Resource sharing and communication across a network

D) Real-time processing

Answer: C) Resource sharing and communication across a network

Question 9: What role does the kernel play in managing hardware resources in an operating system?

A) Providing a user interface

B) Allocating storage space

C) Managing hardware resources

D) Running applications

Answer: C) Managing hardware resources

Question 10: Which of the following is an example of a monolithic kernel?

A) Windows NT

B) QNX

C) Linux

D) MINIX

Answer: C) Linux