Introduction To Operating Systems

This section explores the fundamental concepts of operating systems, detailing their roles, historical evolution, structures, services, operations, and hardware support.

What Is An Operating System?

An operating system (OS) is system software that manages computer hardware and software resources, providing essential services for application programs.

Operating System Structure

The section explores various architectural structures of operating systems, highlighting their features, advantages, and disadvantages.

Operating System Operations

This section explores the fundamental operations of operating systems, including bootstrapping, system calls, and the critical services provided by the OS.

Hardware Support For Os

This section discusses the critical hardware mechanisms necessary for modern operating systems to function securely and manage resources effectively.

What Is An Operating System?

Definition And Core Purposes Of An Operating System

An operating system (OS) is essential software that manages hardware and software resources in a computer, allowing for efficient operation and user interaction.

Evolution Of Operating Systems

This section discusses the evolution of operating systems from the 1940s to present, detailing each generation's characteristics, advantages, and limitations.

Services Provided By An Operating System

An operating system (OS) provides essential services that ensure efficient program execution, manage resources, and facilitate user interactions, contributing to a robust computing environment.

Operating System Structure

"Operating System Structure" explores the fundamental architectural designs for organizing an OS's internal components. It covers **Monolithic Systems**, where the entire kernel is a single, privileged block; **Layered Approach**, which arranges the OS in a strict hierarchy; **Microkernels**, which minimize privileged code and move services to user-level servers; and **Modules**, a hybrid approach (like Linux LKMs) allowing dynamic loading of components for flexibility while maintaining kernel performance. Each structure presents distinct trade-offs in complexity, performance, reliability, and extensibility.

Monolithic Systems

Monolithic systems are a type of operating system architecture that compiles all components into a single executable, allowing direct interaction within a unified address space.

Layered Approach

The layered approach structures an operating system into a hierarchy of layers, each built upon the functionalities of the lower layers, facilitating better organization and maintainability.

Microkernels

Microkernels aim to reduce the amount of code executed in kernel mode, running essential services in user mode to enhance reliability and security.

Modules (E.g., Linux Kernel Modules)

This section discusses the modular approach used in modern operating systems like Linux, where certain functionalities can be dynamically loaded and unloaded without recompiling the entire kernel.

Operating System Operations

"Operating System Operations" delves into the dynamic processes that define how an OS functions, starting with **Bootstrapping**, the sequence of events from power-on to OS readiness, involving firmware (BIOS/UEFI), boot loaders, and kernel initialization. It then explains **System Calls**, the crucial programmatic interface enabling user programs to request privileged services from the kernel, involving a trap mechanism to switch between user and kernel modes for secure interaction.

Bootstrapping

Bootstrapping is the process of starting a computer from a powered-off state to a fully operational state by loading the operating system.

System Calls

System calls provide the essential interface for user applications to interact with the operating system's kernel, allowing them to access hardware and perform privileged operations.

Operating System Services

Operating System Services encompass the essential functionalities provided by an OS, managing both system resources and user/application interaction.

User And Kernel Mode

This section details the operational modes of modern operating systems, specifically user mode and kernel mode, emphasizing their significance in system stability and security.

Hardware Support For Os

"Hardware Support for OS" details the essential hardware mechanisms that underpin operating system functionality, security, and efficiency. Key components include **CPU protection (dual-mode operation)**, distinguishing between privileged kernel mode and restricted user mode for security; **Memory protection**, preventing unauthorized memory access; **Hardware timers**, crucial for time-sharing and preventing infinite loops; and the **Interrupt/Trap System**, which allows hardware or software events to asynchronously gain kernel attention for event handling and system call processing. Without these, no modern OS could provide its fundamental services or ensure robust operation.

Cpu Protection (Dual Mode Operation)

CPU protection is enforced through dual-mode operation, distinguishing between user mode and kernel mode, ensuring system integrity and resource control.

Memory Protection

Memory protection is a critical mechanism in operating systems that ensures a program only accesses its allocated memory space, preventing interference with other programs and the OS kernel.

Timer

The timer is a crucial hardware mechanism in operating systems, responsible for generating interrupts to manage CPU tasks effectively.

Interrupts And Traps

Interrupts and traps are crucial mechanisms by which the OS regains control from running programs and responds to urgent events.