Introduction to Operating System..pdf

Introduction to Operating System Content LO1. Describe the general organization of a computer system LO2. Describe the interaction of operating systems to other components of a computer LO3. Understand the concept of interrupts, and how and why a processor uses interrupts. Operating System “An...

Introduction to Operating System Content LO1. Describe the general organization of a computer system LO2. Describe the interaction of operating systems to other components of a computer LO3. Understand the concept of interrupts, and how and why a processor uses interrupts. Operating System “An operating system is software that manages a computer’s hardware. It also provides a basis for application programs and acts as an intermediary between the computer user and the computer hardware.” – (OS Concepts 10th Ed.) Operating System ▪ ‘Executive Manager’ ▪ Part of the computing system that manages all of the hardware and all of the software ▪ Controls every device, section of memory, and nanosecond of processing time ▪ Controls who can use the system and how ▪ Program running at all times on a computer with all other programs being application programs ▪Without OS, no applications can be run  Examples of OS Windows Linux Ubuntu Android OS Architecture OS Architecture ▪ Kernel is the most central part of the operating systems. OS Architecture ▪ The shell represents software that provides an interface for the user where it serves to launch or start some program for which the user gives instructions. OS Architecture The application represents the software that a user is running on an operating system it can be either system or application software eg slack, sublime text editor, etc. Shell vs. User Application ▪A shell and application are technically the same thing. What differs is the purpose they fulfill. ▪ The purpose of a shell is to work with the kernel so you can create files, get info and such ▪ While the purpose of an application is to aid the user in fulfilling a specific task like writing a report or designing a structure Computer System Structure 1. Hardware - Provides basic computing resources - CPU, memory, I/O devices 2. Operating system - Controls and coordinates use of hardware among various applications and users 3. Application programs - Define the ways in which the system resources are used to solve the computing problems of the users - Word processors, compilers, web browsers, database systems, video games 4. Users - People, machines, other computers Operating System Objectives Execute user programs and make solving user problems easier Convenience: An OS makes a computer more convenient to use Efficiency: An OS allows the computer system resources to be used in an efficient manner. Ability to evolve: An OS should be constructed in such a way as to permit the effective development, testing, and introduction of new system functions without interfering with service. OS SERVICES Computer System Organization Computer-System Operation I/O devices and the CPU can execute concurrently Each device controller is in charge of a particular device type Each device controller has a local buffer CPU moves data from/to main memory to/from local buffers I/O is from the device to local buffer of controller Device controller informs CPU that it has finished its operation by causing an interrupt OS as a resource allocator Manages all resources Decides between conflicting requests for efficient and fair resource use OS is a control program Controls execution of programs to prevent errors and improper use of the computer The one program running at all times on the computer is the kernel. System programs, which are associated with the operating system but are not necessarily part of the kernel Application programs, which include all programs not associated with the operation of the system. Computer Startup bootstrap program is loaded at power-up or reboot ◦Typically stored in ROM or EPROM, generally known as firmware ◦Initializes all aspects of system ◦Loads operating system kernel and starts execution Interrupts Virtually all computers provide a mechanism by which other modules (I/O, memory) may interrupt the normal sequencing of the processor. Interrupts are provided primarily as a way to improve processor utilization. Common Functions of Interrupts Interrupt transfers control to the interrupt service routine generally, through the interrupt vector, which contains the addresses of all the service routines Interrupt architecture must save the address of the interrupted instruction A trap or exception is a software-generated interrupt caused either by an error or a user request An operating system is interrupt driven Classes of Interrupts 1. Program - Generated by some condition that occurs as a result of an instruction execution, such as arithmetic overflow, division by zero, attempt to execute an illegal machine instruction, or reference outside a user’s allowed memory space. 2. Timer - Generated by a timer within the processor. This allows the operating system to perform certain functions on a regular basis. 3. I/O - Generated by an I/O controller, to signal normal completion of an operation or to signal a variety of error conditions. 4. Hardware failure - Generated by a failure, such as power failure or memory parity error. Interrupt Handling The operating system preserves the state of the CPU by storing registers and the program counter Determines which type of interrupt has occurred Separate segments of code determine what action should be taken for each type of interrupt Storage Definitions and Notation Review The basic unit of computer storage is the bit. A bit can contain one of two values, 0 and 1 A byte is 8 bits, and on most computers it is the smallest convenient chunk of storage. Computer storage, along with most computer throughput, is generally measured and manipulated in bytes and collections of bytes. A kilobyte, or KB, is 1,024 bytes A megabyte, or MB, is 21,024 bytes A gigabyte, or GB, is 31,024 bytes A terabyte, or TB, is 41,024 bytes A petabyte, or PB, is 51,024 bytes Storage Structure Main memory – only large storage media that the CPU can access directly ◦ Random access ◦ Typically volatile RAM ROM Secondary storage – extension of main memory that provides large nonvolatile storage capacity Ex.) HDD SSD CD DVD Floppy Disk Hard disks – rigid metal or glass platters covered with magnetic recording material ◦ Disk surface is logically divided into tracks, which are subdivided into sectors ◦ The disk controller determines the logical interaction between the device and the computer Solid-state disks–faster than hard disks, nonvolatile ◦ Various technologies ◦ Becoming more popular Storage Hierarchy Storage systems organized in hierarchy ◦Speed ◦Cost ◦Volatility Caching – copying information into faster storage system; main memory can be viewed as a cache for secondary storage Device Driver for each device controller to manage I/O ◦ Provides uniform interface between controller and kernel Volatile storage - loses its contents when the power to the device is removed Nonvolatile storage (NVM) retains its contents when power is lost. ◦ Mechanical - examples are HDDs, optical disks, holographic storage, and magnetic tape. ◦ Electrical - examples are flash memory, FRAM, NRAM, and SSD. (Referred to as NVM.) References: What is Operating System (OS)? Defintion and Functions – javatpoint What is Operating System? Explain Types of OS, Features and Examples (guru99.com) Operating System Tutorial | Tutorialspoint https://old.amu.ac.in/emp/studym/100003811.pdf