01 381CCS_CHAPTER1 - 1445 - S1.pdf

COURSE NAME : OPERATING SYSTEM COURSE CODE : 381CCS-3 CHAPTER 1 : INTRODUCTION TO OPERATING SYSTEM SUBJECT COORDINATOR: Dr. Aymen TRIGUI SUBJECT TEACHER: Dr. B.Prasanalakshmi Dr. Harish College of Computer Scence...

COURSE NAME : OPERATING SYSTEM COURSE CODE : 381CCS-3 CHAPTER 1 : INTRODUCTION TO OPERATING SYSTEM SUBJECT COORDINATOR: Dr. Aymen TRIGUI SUBJECT TEACHER: Dr. B.Prasanalakshmi Dr. Harish College of Computer Scence DEPARTMENT OF COMPUTER SCIENCE KING KHALID UNIVERSITY Course Specification Text Book Page Chapter No TOPICS CHAPTERS / SECTION Number Book Reference “Operating Introduction to Operating Systems CHAPTER 1 System What Operating System Do 1.1 3-7 Concepts”, 10th Computer System Organization: Storage 7,8, 11- Edition, structure-I/O structure 1.2 ( 1.2.1, 1.2.2, 1.2.3) 15 Abraham Silber 1 Schatz , Computer System Architecture: Single Peter Baer Processor Systems–Multi processor Galvin, Systems-Clustered Systems 1.3(1.3.1, 1.3.2,1.3.3) 15-21 Greg Gagne , Wiley, 2018 Distributed systems 1.8 35,36 CHAPTER 1 : INTRODUCTION TO OPERATING SYSTEM  Introduction  What Operating System Do  Computer System Organization  Storage structure  I/O structure  Computer System Architecture  Single Processor Systems  Multi processor Systems  Clustered Systems  Distributed System 2 1.1 INTRODUCTION 1.1.1 WHAT IS AN OPERATING SYSTEM?  A program that acts as an intermediary between a user of a computer and the computer hardware.  Operating system goals: Execute user programs and make solving user problems easier. Make the computer system convenient to use. Use the computer hardware in an efficient manner. 3  1.1.2 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 4 1.1.3 ABSTRACT VIEW OF COMPONENTS OF COMPUTER Figure 1.1 Abstract view of the components of a computer system. 5  1.2 WHAT OPERATING SYSTEMS DO Depends on the Users point of view  Users want convenience, ease of use and good performance Don’t care about resource utilization  Mobile devices like smartphones and tablets are resource poor, optimized for usability and battery life Mobile user interfaces such as touch screens, voice recognition  Some computers have little or no user interface Ex : Embedded computers in devices and automobiles: Operating systems and applications are designed primarily to run without user intervention Depends on System View Operating System is viewed as  Resource Allocator : A computer system has many resources to solve a problem like CPU time, memory space, storage space, I/O devices, and so on. The operating system acts as the manager of these resources.  Control Program : controls the execution of user programs and operations of I/O devices 6 1.2.1 OPERATING SYSTEM DEFINITION  No universally accepted definition  “The one program running at all times on the computer” is the kernel, part of the operating system  Everything else is either A system program (ships with the operating system, but not part of the kernel) , or An application program, all programs not associated with the operating system  Today’s OSes for general purpose and mobile computing also include middleware – a set of software frameworks that provide additional services to application developers such as databases, multimedia, graphics 7 1.3 COMPUTER SYSTEM ORGANIZATION  Computer system consists of one or more CPUs and a number of device controllers connect through common bus providing access to shared memory  Concurrent execution of CPUs and devices competing for memory cycles  I/O devices and the CPU can execute concurrently  Each device controller is in charge of a particular device type and has a local buffer  Operating systems have a device driver for each device controller to manage it  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. 8 Figure 1.2 A typical PC computer system 1.3.1 STORAGE STRUCTURE Random access Memory (RAM) or Main Memory :  Computers run most of their programs from this rewritable memory.  It is the only large storage media that the CPU can access directly.  Loses its content when power is turned off (Volatile).  Main memory commonly is implemented in a semiconductor technology called dynamic random-access memory (DRAM). BootStrap Program:  It is Loaded at Power up or reboot.  The first program to run on computer power-on and loads Operating System Kernel and starts Execution  Typically stored in ROM or EPROM, generally known as firmware Secondary storage: Extension of main memory that provides large nonvolatile (permanent) storage capacity i) Hard Disk Drives (HDD)  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 9 ii) Non-volatile memory (NVM) devices  Which provide storage for both programs and data.  Faster than hard disks, nonvolatile  1.3.1.1 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 10 Figure 1.3 Storage-device hierarchy 1.3.2 I/O STRUCTURE  Two methods for handling I/O After I/O starts, control returns to user program only upon I/O completion Wait instruction idles the CPU until the next interrupt Wait loop (contention for memory access) At most one I/O request is outstanding at a time, no simultaneous I/O processing After I/O starts, control returns to user program without waiting for I/O completion System call – request to the OS to allow user to wait for I/O completion Device-status table contains entry for each I/O device indicating its type, address, and state OS indexes into I/O device table to determine device status and to modify table entry to include interrupt Direct Memory Access Structure Used for high-speed I/O devices able to transmit information at close to memory speeds Device controller transfers blocks of data from buffer storage directly to 11 main memory without CPU intervention Only one interrupt is generated per block, rather than the one interrupt per byte 1.4 COMPUTER SYSTEM ARCHITECTURE 1.4.1 Single-Processor System Have only a single processor or CPU, Shared between users by dividing the CPU time into time-slices and allocating one of these to each user in turn The time-slices are very short, giving each user the impression that their programs are running continuously 1.4.2 Multiprocessor System(Parallel System) Parallel systems with more than one CPU in close communication Tightly coupled system – processors share memory and a clock; communication usually takes place through the shared memory Advantages  Increased throughput  Economy of scale  Increased reliability – graceful degradation or fault tolerance 12  COMPUTER SYSTEM ARCHITECTURE(CONT…) Two types: Asymmetric Multiprocessing  Each processor is assigned a specific task.  Master processor schedules and allocated work to slave processors.  More common in extremely large systems Symmetric Multiprocessing  each processor performs all tasks  Each processor runs and identical copy of the operating system.  Many processes can run at once without performance deterioration.  Most modern operating systems support SMP 13 Figure 1.4 Symmetric multiprocessing architecture.  COMPUTER SYSTEM ARCHITECTURE(CONT…) 1.4.3 Clustered Systems  Like multiprocessor systems, but multiple systems working together  Usually sharing storage via a storage-area network (SAN)  provides a high-availability service which survives failures Two types: Asymmetric clustering  has one machine in hot-standby mode and other is running the applications.  The hot-standby host machine does nothing but monitor the active server.  If that server fails, the hot-standby host becomes the active serve Symmetric clustering  has multiple nodes running applications, monitoring each other  Efficient as it uses all of the available hardware.  it does require that more than one application be available to run. 14 Figure 1.5 General structure of a clustered system. 1.5 DISTRIBUTED SYSTEM  Loosely coupled system – each processor has its own local memory; processors communicate with one another through various communications lines, such as high-speed buses or telephone lines.  Requires Networking infrastructure Local Area Network (LAN) Wide Area Network (WAN) Metropolitan Area Network (MAN) Personal Area Network (PAN)  Network Operating System - provides features between systems across network Communication scheme allows systems to exchange messages Illusion of a single system  Advantages Resources sharing Computation speed up – load sharing Reliability Communications 15