Operating System: Basic Concepts of Computer System Operations

Introduction

• Review of the last lecture: Introduction to Operating Systems
• Today's focus: Basic concepts needed to understand Operating Systems, specifically the structure of the computer system
• Importance of understanding computer system structure for grasping how operating systems work

Modern General Purpose Computer System

• Consists of one or more CPUs (central processing units)
• CPUs: The brain of the computer; responsible for all computations and processing
• Common misconceptions about CPU: It's not the entire box, but a small chip on the motherboard
• Device controllers connected via a common bus to shared memory

Components and Their Connections

• CPU: Central processing unit
• Device Controllers: Control specific types of devices (e.g., disk controller, USB controller, video adapter)
• Common Bus: Connects the CPU and device controllers
• Shared Memory: Accessed by the CPU and device controllers for executing tasks

Key Points

• Device controllers handle the functioning of specific hardware devices
• CPU and device controllers can execute tasks concurrently (simultaneously)
• Importance of memory controllers to ensure orderly, synchronized access to shared memory

Terms and Concepts

Bootstrap Program

• The initial program run when a computer is powered up or rebooted
• Stored in ROM (Read Only Memory)
• Responsible for loading the OS and starting execution
• Loads the OS kernel into the main memory

Interrupt

• Triggered by hardware or software, signals the CPU to stop its current task and execute a different task
• Interrupts can be hardware-initiated or software-initiated (system call/monitor call for software)
• CPU stops current work, executes the interrupt service routine, and then resumes its previous task

System Call (Monitor Call)

• A type of interrupt triggered by software
• Executed via a special operation called a system call

Response to Interrupts

• Step 1: CPU is interrupted and stops its current task
• Step 2: Transfers execution to the starting address of the interrupt service routine (ISR)
• Step 3: ISR executes
• Step 4: CPU resumes the interrupted task upon completion of the ISR

Summary

• Basic introduction to computer system operations
• Explanation of the structure and functioning of the computer system components
• Discussion on Bootstrap programs, interrupts, and system calls
• Next lecture: Storage structures and memory