operating system of the computer/PC/laptop.pptx

Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edit9on
Chapter 1: Introduction

1.2 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Chapter 1: Introduction
 OS: Introduction to Operating System
1. Introduction to Operating System (OS)
2. What is an Operating System (OS)
3. Types of Operating System (OS)
4. Functions of Operating System (OS)
5. Goals of Operating System (OS)
 OS: Basics of OS (Storage Structure)
1. Basics of Operating System.
2. Storage Structure.
3. Hierarchy of Storage devices.
4. Main memory and Secondary memory.
5. Volatile and Non-Volatile devices.

Objectives
 To describe the basic organization of computer systems
 To provide a grand tour of the major components of operating systems
 To give an overview of the many types of computing environments
 To explore several open-source operating systems

What is an Operating System?
 A program that acts as an intermediary between a user of a computer
and the computer hardware
Figure 1.1 Abstract view of the components of a computer system.

Computer System Structure
 Computer system can be divided into four components:
 Hardware – provides basic computing resources
 CPU, memory, I/O devices
 Operating system
 Controls and coordinates use of hardware among various
applications and users
 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
 Users
 People, machines, other computers

Types Operating Systems
 Batch OS
 Time sharing OS
 Distributed OS
 Network OS
 Real time OS
 Multi-Programming/Multi-Processing/Multi-Tasking OS

Functions of Operating Systems
 OS is 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
 An Operating System does the following activities for memory
management −Management of memory
 Keeps tracks of primary memory, i.e., what part of it are in use by
whom, what part are not in use.
 In multiprogramming, the OS decides which process will get
memory when and how much.
 Allocates the memory when a process requests it to do so.
 De-allocates the memory when a process no longer needs it or
has been terminated.

Functions of OS (Cont.)
 An Operating System does the following activities for file
management
 Keeps track of information, location, uses, status etc. The
collective facilities are often known as file system.
 Decides who gets the resources.
 Allocates the resources.
 De-allocates the resources.
 No universally accepted definition
 “The one program running at all times on the computer” is the kernel.
Everything else is either a system program (ships with the operating
system) or an application program.

Goals of Operating System
Operating systems exist because they are supposed to make it easier to
access processing for the needs of the user. This is particularly clear
when you look at operating system for small personal computers.
 The primary goal of an operating system is a convenience for the
user- Convenience
 A secondary goal is Efficiency.
This goal is particularly important for large, shared multi-user systems.
 Both
Sometimes these two goals, convenience and efficiency, are
contradictory and are always design considerations by system
developers to optimize the overall utility of the computer for the needs of
the users and the computer system.

Computer System Organization
 Computer-system operation
 A modern general-purpose computer system consist of one or
more CPUs and number of device controllers connected through
common bus that provides access to shared memory.

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

Computer Startup and Interrupt
 Some important terms:
 Bootstrap Program- The initial program that runs when a computer is powered up or rebooted.
 It is stored in the ROM.
 It must know how to load the OS and start executing that system.
 It must locate and load in to memory the OS kernel.
 Interrupt-The occurrence of an event is usually signaled by an Interrupt from Hardware or software.
 Hardware may trigger an interrupt at any time by sending a signal to the CPU, usually by the way of
the system bus.
 System Call (Monitor Call) –Software may trigger an interrupt by executing a special operation called
system call

Common Functions of Interrupts
 When the CPU is interrupted, it stops what it is doing and
immediately transfers execution to a fixed location.
 The fixed location usually contains the starting addresses where the
service routine of the interrupt is located.
 Interrupt Service Routine executes.
 On completion, the CPU resumes the interrupted computation.
 Interrupt architecture must save the address of the interrupted
instruction
 An operating system is interrupt driven

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:
 polling
 vectored interrupt system
 Separate segments of code determine what action should be taken for
each type of interrupt

Interrupt Timeline

I/O Structure
 Storage is only one of many types of I/O devices within a compute.
 A large portion of OS codes is dedicated to managing I/O , both
because of its importance to the reliability and performance of a
system and because of the varying nature of the devices.
 A general purpose computer system consists of CPUs and multiple
device controller that are connected through a common bus.
 Each device controller is in charge of a specific type of device
maintains
Local Buffer Storage Set of Special Purpose
Registers
 Typically, Operating systems have a device driver for each device
controller.
 This device driver understands the device controller and presents a
uniform interface to the device to the rest of the operating system.

 To start an I/O operation, the device driver loads the appropriate
registers within the device controller.
 The device controller, in turn, examines the contents of these
registers to determine what action to take
 The controller starts the transfer of data from the device to its local
buffer.
 Once the transfer of data is complete, the device controller informs
the device driver via an interrupt that it has finished its operation.
 The device driver then returns control to the OS.
To solve this problem, Direct Memory Access(DMA) is used.
This form of interrupt-driven I/O is fine for small amounts of
data but can produce high overhead when used for bulk
data movement.
Working of an I/O Operation

Direct Memory Access Structure
 After setting up buffers, pointers and counters for the I/O device
controller transfers an entire block of data directly to or from its own
buffer storage to memory, with no intervention by the CPU.
 Device controller transfers blocks of data from buffer storage directly to
main memory without CPU intervention
 Only one interrupt is generated per block, rather than the one interrupt
per byte.

Working of an I/O Operation

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. All other storage in a computer is based on collections of bits. Given enough
bits, it is amazing how many things a computer can represent: numbers, letters,
images, movies, sounds, documents, and programs, to name a few. A byte is 8
bits, and on most computers it is the smallest convenient chunk of storage. For
example, most computers don’t have an instruction to move a bit but do have one
to move a byte. A less common term is word, which is a given computer
architecture’s native unit of data. A word is made up of one or more bytes. For
example, a computer that has 64-bit registers and 64-bit memory addressing
typically has 64-bit (8-byte) words. A computer executes many operations in its
native word size rather than a byte at a time.
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 1,0242 bytes; a gigabyte, or GB, is 1,0243 bytes; a
terabyte, or TB, is 1,0244 bytes; and a petabyte, or PB, is 1,0245 bytes.
Computer manufacturers often round off these numbers and say that a megabyte is
1 million bytes and a gigabyte is 1 billion bytes. Networking measurements are an
exception to this general rule; they are given in bits (because networks move data a
bit at a time).

Storage Structure
 Main memory – only large storage media that the CPU can access
directly
 Random access
 Typically volatile
 Secondary storage – extension of main memory that provides large
nonvolatile storage capacity
 Magnetic 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 magnetic 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

Storage-Device Hierarchy

Caching
 Important principle, performed at many levels in a computer (in
hardware, operating system, software)
 Information in use copied from slower to faster storage temporarily
 Faster storage (cache) checked first to determine if information is
there
 If it is, information used directly from the cache (fast)
 If not, data copied to cache and used there
 Cache smaller than storage being cached
 Cache management important design problem
 Cache size and replacement policy

Computer System Architecture
 How we Categorized the computer system based on the general Purpose Processors.

Single Processor System

Multi-Processor System

Types of Multi-Processor Systems

Clustered Systems

Students Task
List Open Source Operating Systems

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