OS-01.ppt
- 1. OPERATING SYSTEMS Course Objectives: Learn basics of operating Systems. Understand the process management and synchronization that take place in the operating system. Learn the principles of memory, I/O and file management in a secured environment 12/21/2022 Unit-I: Introduction 1
- 2. COURSE OUTCOMES: At the end of this course the student will be able to Outline the basic functionalities and structure of the Operating System Analyze various Process Scheduling algorithms, distinguish between various types of Operating systems like Windows and Linux. Solve issues related to process Synchronization and Deadlocks in the Operating System Demonstrate the concepts of Memory Management(Physical and Virtual memory) Infer the directory structure and analyze disk management algorithms. understand the concepts of I/O systems, protection and security 12/21/2022 Unit-I: Introduction 2
- 3. Syllabus • UNIT I : Introduction to Operating System • UNIT II: Process Management • UNIT III: Process-Synchronization & Deadlocks • UNIT IV: Memory Management • UNIT V: File System • UNIT VI: I/O Systems 12/21/2022 Unit-I: Introduction 3
- 4. UNIT–I: Introduction 1. Introduction to Operating System Concepts • Multitasking • Multiprogramming • Multiuser • Multithreading • Multi processing 2. Types of Operating Systems • Batch Operating System • Time–sharing Systems • Distributed OS • Network OS • Real–Time OS 3. Various Operating System Services 4. Architecture 5. System Calls and Programs Exam Questions Unit-I: Introduction 4
- 5. |<< Introduction to Operating System Concepts • Prerequisites • Operating System (OS) • Resources of a Computer System • User View • System View • Objectives and Functions of OS • Multiprogramming • Multitasking • Multiuser • Multithreading Unit-I: Introduction 5
- 6. • Data Structures • Computer Organisation • Any High–Level Language (C, …) Unit-I: Introduction 6 |<< Prerequisites
- 7. Defn1: OS is software that manages computer hardware and software resources and provides common services for computer programs. (source: Wiki) Defn2: Controls and coordinates use of Hardware among Various Applications and Users Defn3:Collection of System Software (Programs), which makes it User friendly and Most efficient Kernel Program running at all times on the Computer Unit-I: Introduction 7 Operating System (OS)
- 8. Kernel • Central module and Part of the OS that loads first, and it remains in main memory. • So, it has to be as small as possible while still providing all the essential services required by other parts of the operating system and applications. • Its loaded into a protected area of memory to prevent it from being overwritten by programs or other parts of the operating system. • Responsible for memory management, – process and task management, and – disk management. – The kernel connects the system hardware to the application software. • Every OS has a kernel. • For example the Linux kernel is used in numerous operating systems including Linux, FreeBSD, Android and others. Unit-I: Introduction 8
- 9. • AT & T / BSD Unix • Sun Microsystems’ Solaris 2 Linux • Microsoft MS-DOS Windows 95 / 98 / NT Windows 2000 (Windows Me) Windows XP Windows Vista Windows 7 / Windows 8 Windows 10 • DEC VMS (Virtual Memory System) TOPS–20 (Total Operations Processing System) • IBM OS/2 • Apple Macintosh Unit-I: Introduction 9 |<< Most Popular Operating Systems
- 10. • Hardware • Operating System • Application Programs • Users Unit-I: Introduction 10 Basic Structure/Components of a Computer System 1. Central Processing Unit (CPU) 2. Memory 3. Input–Output (I/O) / Peripheral Devices • Provides basic Computing Resources.
- 11. Hardware and Software required to solve a problem CPU Time Memory Space File Storage Space I/O Devices … Unit-I: Introduction 11 |<< Resources of a Computer System Four Components of Computer System
- 12. Varies according to the interface used Goal To maximize the work, the user is performing • Ease of use • Performance • Resource utilization Mainframe / Minicomputer • Share Resources • Exchange Information • Designed to maximize Resource utilization All Available CPU Time, Memory and I/O used efficiently Unit-I: Introduction 12 User View
- 13. • Workstations (Perform Effective Resource Sharing) • Connected to Networks of other workstations and Servers • Dedicated Resources at disposal • Also Share Resources such as Networking and Servers (File, Compute, Print Servers) • Handheld Computers (Ease of use) • Standalone units for Individual users • Connected to Networks (Directly by wire / through wireless Modems and Networking) • Perform relatively few remote operations (Power, Speed, Interface limitations) • Designed mostly for individual usability • Embedded Computers in Home Devices and Automobiles (Performance) • Have Numeric Keypads • May turn indicator lights on or off to show status • Designed primarily to run without user intervention Unit-I: Introduction 13 User View (contd.)
- 14. Most intimately involved with Hardware • Resource Allocator •Acts as Manager of Resources. •Decides to allocate Resources to Specific Programs and Users so that OS operates the Computer System Efficiently and Fairly •Important as many Users access the same Mainframe / Minicomputer • Control Program •Manages Execution of User Programs to prevent Errors and Improper use of Computer •Concerned with Operation and Control of I/O Devices Unit-I: Introduction 14 System View
- 15. Essential part of a Computer System • Purpose: To provide an environment in which a User can Execute Programs in a Convenient and Efficient manner • Program that acts as an intermediary between the User of a Computer and the Computer Hardware • Must Ensure Correct Operation of Computer System • Provides Certain Services to Programs and users of those programs in order to make their Tasks Easier • Controls and Coordinates the use of Hardware among Various Application Programs for the Various users • Primary Goals- User friendly Efficient Operation of the Computer System Unit-I: Introduction 15 Objectives and Functions of Operating System
- 16. Computer System Organization • Computer-system operation – One or more CPUs, device controllers connect through common bus providing access to shared memory – Concurrent execution of CPUs and devices competing for memory cycles
- 17. Storage-Device Hierarchy •The higher levels are expensive, but are fast. •As we move down the hierarchy, the cost per bit decreases, where as Access time generally increases.
- 18. Computer-System Architecture 1.Single-Processor Systems 2.Multi-Processor Systems 3.Clustered Systems Unit-I: Introduction 18
- 19. Computer-System Architecture • Single Processor Systems – One CPU – May have other special-purpose processors (such as disk controllers) • Run a limited instruction set • Do not run user processes • Sometimes managed by OS • For example a disk controller processor receives a sequence of requests from the main CPU and implements its own disk queue and scheduling algorithm to relieve the main CPU of the overhead of disk scheduling.
- 20. Multiprocessor systems • Two or more processors in close communication, sharing the computer bus and sometimes the clock, memory, and peripherals. • Advantages: – Increased throughput • The speed-up ratio with N processors is not N however, it is less than N. – Economy of scale • Sharing of peripherals, mass storage, power supplies. • Can cost less than multiple single-processor systems – Increased reliability • Graceful degredation(The ability to continue providing service proportional to the level of surviving hardware) • Fault tolerance – Failure detection, diagnose and correction – Hardware duplication(HP NonStop system)
- 21. Multiprocessor Systems • Two types: – Asymmetric multiprocessing in which each processor is assigned a specific task. A master processor controls the system, scheduling and allocating work to slave processors. – Symmetric multiprocessing (SMP) in which each processor performs all tasks within the operating system. All processors are peers.
- 23. Clustered Systems • Gather together multiple CPUs to accomplish computation • Composed of two or more individual systems coupled together. • High availability service. – Each node can monitor one or more of the others over the LAN. – If the monitored machine fails, the monitoring machine can take ownership of its storage and restart the applications that were running on the failed machine. • Structure – Asymmetric clustering: One machine is in hot-standby mode while the other is running applications. Hot-standby machine only monitors the active server. – Symmetric clustering:Two or more hosts are running applications and are monitoring each other • Parallel Clusters allow multiple hosts to access the same data on the shared storage. May need a distributed lock manager (DLM).
- 24. • Single User System • Single Program in execution. Unit-I: Introduction 24 Uniprogramming
- 25. Unit-I: Introduction 25 Multiprogramming Systems Multiprogramming is also the ability of an operating system to execute more than one program on a single processor machine. More than one task/program/job/process can reside into the main memory at one point of time. A computer running excel and firefox browser simultaneously is an example of multiprogramming.
- 26. Time sharing is a logical extension of multiprogramming. In this, the CPU executes multiple jobs by switching among them, but the switches occur so frequently that the users can interact with each program while it is running. Response time should be < 1 second Each user has at least one program executing in memory process Job scheduling: Which jobs to bring to memory from job pool on disk. If several jobs ready to run at the same time CPU scheduling If processes don’t fit in memory, swapping moves them in and out to run Virtual memory allows execution of processes not completely in memory (physical memory versus logical memory) Unit-I: Introduction 26 |<< Time Sharing
- 27. • Multiple Tasks are performed during the Same period of time. • Tasks Share Common Processing Resources such as CPU and Main Memory. • In Uniprocessor Systems, Multitasking Solves the problem by Scheduling which task may be the one running at any given time, and when another waiting task gets a turn. Context Switch • Act of reassigning a CPU from one task to another one. Unit-I: Introduction 27 |<< Multitasking / Multiprocessing Allows for Multiple users to use the Same Computer in timely manner. Multiuser
- 28. Unit-I: Introduction 28 Multitasking Multitasking is the ability of an operating system to execute more than one task simultaneously on a single processor machine. Though we say so but in reality no two tasks on a single processor machine can be executed at the same time. Actually CPU switches from one task to the next task so quickly that appears as if all the tasks are executing at the same time. More than one task/program/job/process can reside into the same CPU at one point of time.
- 29. Unit-I: Introduction 29 Multiprocessing Multiprocessing is the ability of an operating system to execute more than one process simultaneously on a multi processor machine. In this, a computer uses more than one CPU at a time.
- 30. Unit-I: Introduction 30 Multithreading Multithreading is the ability of an operating system to execute the different parts of a program called threads at the same time. Threads are the light wait processes which are independent part of a process or program. In multithreading system, more than one threads are executed parallely on a single CPU.
- 31. • Batch Processing Systems • Interactive Systems • Time Sharing • Time Slicing • Distributed Systems • Network Systems • Real–Time Systems • Evolution of OS Unit-I: Introduction 31 Types of Operating Systems |<<
- 32. Computer runs one and only one application at a time. In Batch processing same type of jobs batch (BATCH- a set of jobs with similar needs) together and execute at a time. The OS was simple, its major task was to transfer control from one job to the next. The job was submitted to the computer operator in form of punch cards. At some later time the output appeared. The OS was always resident in memory. Common Input devices were card readers and tape drives. Common output devices were Line printers ,Tape drives Card punches Unit-I: Introduction 32 Batch Processing Systems
- 34. OS always resident in memory. CPU is often idle. User did not interact directly with computer systems. User prepared a job and submitted to computer operator. Operators batched together jobs with similar needs and run them through the computer as a group. Programmers would leave their programs with the operator. The operator would sort the programs into batches with similar requirements and as the computer became available would run each job. Unit-I: Introduction 34 |<< Batch Processing (during earlier days)
- 36. • The User interacts directly with OS to supply commands and data as the application program executes and the user receives results of processing immediately. • User and Computer System interact. • User Requests. • System Responds. • The process goes on. Unit-I: Introduction 36 |<< Interactive Processing
- 37. •There will be an user interface in place to allow all these to happen •It can be CLI or GUI Unit-I: Introduction 37
- 38. Variable CPU Time to different processes. Once CPU Time is allocated to a process, will not be interrupted till it completes its execution, or waiting for an I/O, or cannot continue its execution. Unit-I: Introduction 38 |<< Time Sharing Equal Amount of CPU time allocated among Various Processes. Time Slicing
- 39. • Distribute the Computation among Several Physical Processors 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 •Enables Parallelism but speed up is not the goal Advantages of Distributed Systems • Resources Sharing • Computation Speed up–load Sharing • Reliability • Communications Unit-I: Introduction 39 Distributed Systems
- 44. Special purpose OS. Used when rigid time requirements have been placed on the operation of a processor or the flow of data. Used as control device in a dedicated application. Sensors bring data to the computer. The computer analyses the data and possibly adjust controls to modify the sensor inputs. Well-defined, Fixed-time constraints. Processing must be done within the defined constraints. Ex: Systems controlling scientific experiments Medical imaging systems Industrial control systems Certain display systems Automobile-engine fuel-injection systems Home-appliance controllers Weapon systems Unit-I: Introduction 44 Real–Time Systems
- 45. Hard real-time systems Guarantee critical tasks be completed on time. Soft real-time systems Critical real-time task gets priority over other tasks and retains the priority until it completes. Ex: Multimedia Advanced scientific projects Undersea exploration Planetary rovers Unit-I: Introduction 45 |<< Types of Real–Time Systems
- 47. Evolution of Operating Systems Unit-I: Introduction 47 |<<
- 48. |<< Various Operating System Services Provides No. of Services. Lowest level – System Calls Allow running program to make requests from the OS directly. Higher level – Command Interpreter or Shell User issues request without writing program. Categories 1. Program Control 2. Status Requests 3. I/O Requests Unit-I: Introduction 48
- 49. Operating System Services 1. User Interface 2. Program Execution 3. I/O Operations 4. File-System Manipulation 5. Communications 6. Error Detection Unit-I: Introduction 49 |<< – Other Services 1. Resource Allocation 2. Accounting 3. Protection and Security
- 50. • All Operating Systems have User Interface (UI) • Command-Line Interface (CLI) • Graphics User Interface (GUI) Unit-I: Introduction 50 |<< User Interface • Load Program into Memory • Run the Program • End Execution, either Normally or Abnormally (indicating Error) Program Execution
- 51. Running Program may require I/O, which may involve File or I/O Device. Unit-I: Introduction 51 I/O Operations |<< Programs need to Read and Write Files and Directories, Create and Delete Files and Directories, Search Files and Directories, List File Information, Permission Management. File–System Manipulation
- 52. Processes may exchange information, on the Same Computer or between Computers over a Network Communications may be via – Shared Memory or – thru Message Passing (Packets moved by the Operating System) Unit-I: Introduction 52 Communications |<< Two ways of passing data between programs.
- 53. • May occur in – the CPU and Memory Hardware, – I / O Devices, – User Program • For each type of Error, – OS should take the appropriate action to ensure correct and consistent computing • Debugging facilities – can greatly enhance the User’s and Programmer’s abilities to efficiently use the System Unit-I: Introduction 53 Error Detection |<< When Multiple Users or Multiple Jobs running Concurrently, Resources must be Allocated to each of them. Resource Allocation
- 54. To Keep Track of Which Users use How much What Kinds of Computer Resources To know Usage statistics. Unit-I: Introduction 54 Accounting |<< • Protection – Involves ensuring that all Access to System Resources is Controlled • Security of the System – from outsiders requires User Authentication, – extends to defending External I / O Devices from Invalid Access attempts Protection and Security
- 55. System Calls • Provides Interface between Running Program and the Operating System. • It provides as an interface to the services made available by an OS – These calls are generally available as routines written in C and C++, although certain low-level tasks, may need to be written using assembly-language instructions. • Methods used to Pass Parameters between a Running Program and the Operating System. 1. Pass Parameters in Registers. 2. Store the Parameters in a Table in Memory, and the Table Address is passed as a Parameter in a Register. 3. Push (store) the Parameters onto the Stack by the Program, and Pop off the Stack by Operating System. Unit-I: Introduction 55 |<< System Calls • System Calls • Types of System Calls • System Programs
- 56. System Call Sequence to Copy the contents of One file to another file. Dr. D. S. R. Murthy 56 Unit-I: Introduction |<< Example of System Calls
- 57. 12/21/2022 Unit-I: Introduction 57 The handling of a user application invoking the open() system call
- 58. 12/21/2022 Unit-I: Introduction 58 Passing of Parameters as a table
- 59. Types of System Calls 1. Process Control 2. File Management 3. Device Management 4. Information Maintenance 5. Communications Example Unit-I: Introduction 59 |<<
- 60. • End, Abort • Load, Execute • Create Process, Terminate Process • Get Process Attributes, Set Process Attributes • Wait for time • Wait Event, Signal Event • Allocate and Free Memory Unit-I: Introduction 60 |<< System Calls – Process Control
- 61. • Create File, Delete File • Open, Close • Read, Write, Reposition • Get File attributes, Set File attributes Unit-I: Introduction 61 |<< System Calls – File Management • Request Device, Release Device • Read, Write, Reposition • Get Device attributes, Set Device attributes • Logically Attach or Detach Devices System Calls – Device Management
- 62. Unit-I: Introduction 62 • Get Time or Date, Set Time or Date • Get System Data, Set System Data • Get Process, File, or Device attributes • Set Process, File, or Device attributes |<< System Calls – Information Maintenance Message Passing Vs Shared Memory • Create, Delete Communication connection • Send, Receive Messages • Transfer Status information • Attach or Detach Remote Devices System Calls – Communications
- 63. Unit-I: Introduction 63 System programs provide a convenient environment for program development and execution. They can be divided into: Categories 1. Programming Language Support 2. Program Loading and Execution 3. File Management 4. File Modification 5. Status information 6. Communications |<< System Programs System Calls 1. Process Control 2. File Management 3. Device Management 4. Information Maintenance 5. Communications
- 64. Unit-I: Introduction 64 |<< • Compilers • Assemblers • Interpreters System Programs – Programming Language Support • Absolute Loaders • Relocatable Loaders • Linkage Editors • Overlay Loaders • Debugging Systems System Programs – Program Loading & Execution
- 65. Unit-I: Introduction 65 • Print • Dump • List • Manipulate Files and Directories |<< System Programs – File Management • Create • Delete • Copy • Rename Text Editors To Create and Modify the Contents of Files Stored on Disk or Tape. Screen Editor – vi Line Editor – edlin, ed, … System Programs – File modification
- 66. Unit-I: Introduction 66 |<< Date Time Amount of available Memory / Disk Space No. of users.. •Some ask the system for info - date, time, amount of available memory, disk space, number of users •Others provide detailed performance, logging, and debugging information •Typically, these programs format and print the output to the terminal or other output devices •Some systems implement a registry - used to store and retrieve configuration information System Programs – Status information
- 67. Unit-I: Introduction 67 |<< Provide mechanism for creating virtual connections among processes, users and different computer systems. Allow users to Send messages to one another’s Screens. Browse Web pages. Send Electronic Mail messages. Log-in Remotely. Transfer Files from one machine to another. System Programs – Communications
- 68. Operating System Structure • General-purpose OS is very large program • Various ways to structure ones – Simple structure – MS-DOS – More complex -- UNIX – Layered – an abstraction – Microkernel -Mach
- 69. Simple Structure -- MS-DOS • MS-DOS – written to provide the most functionality in the least space – So, not divided into modules carefully – Although MS-DOS has some structure, its interfaces and levels of functionality are not well separated
- 70. • For instance, application programs are able to access the basic I/O routines to write directly to the display and disk drivers. Such freedom leaves MS-DOS vulnerable to malicious programs, causing entire system crashes when user programs fail. • Ms-DOS is also limited by the hardware
- 71. Non Simple Structure -- UNIX UNIX – initially, limited by hardware functionality, the original UNIX operating system had limited structuring. The UNIX OS consists of two separable parts – Systems programs – The kernel • Consists of everything below the system-call interface and above the physical hardware • Provides the file system, CPU scheduling, memory management, and other operating-system functions; a large number of functions for one level
- 72. Traditional UNIX System Structure Beyond simple but not fully layered
- 73. Layered Approach • The operating system is divided into a number of layers (levels), each built on top of lower layers. The bottom layer (layer 0), is the hardware; the highest (layer N) is the user interface. • With modularity, layers are selected such that each uses functions (operations) and services of only lower-level layers
- 74. Microkernel System Structure • Moves as much from the kernel into user space. This method structures the OS by removing all nonessential components from the kernel and implementing them as system and user-level programs. • Provide minimal process and memory management. • Mach example of microkernel – Mac OS X kernel (Darwin) partly based on Mach • Communication takes place between user modules using message passing • Benefits: – Easier to extend a microkernel – Easier to port the operating system to new architectures – More reliable (less code is running in kernel mode) – More secure • Detriments: – Performance overhead of user space to kernel space communication
- 76. Modules • The best current methodology for operating-system design involves object-oriented programming techniques to create a modular kernel. • Here the kernel has a set of core components and links in additional services during boot time or during run time. • Many modern operating systems implement loadable kernel modules – Uses object-oriented approach – Each core component is separate – Each talks to the others over known interfaces – Each is loadable as needed within the kernel • Overall, similar to layers but with more flexible – Linux, Solaris, etc
- 78. Hybrid Systems • Most modern operating systems are actually not one pure model – Hybrid combines multiple approaches to address performance, security, usability needs – Linux and Solaris kernels in kernel address space, so monolithic, plus modular for dynamic loading of functionality – Windows mostly monolithic • Apple Mac OS X uses hybrid structure. It is a layered system in which one layer consists of the Mach microkernel. • The top layers include application environments and a set of services providing GI to applications. Below is the kernel environment which consists Mach(memory management, RPC, IPC,Thread scheduling, message passing). BSD : provides CL interface, networking and file systems
- 79. Mac OS X Structure
- 80. iOS • Apple mobile OS for iPhone, iPad – Structured on Mac OS X, added functionality – Does not run OS X applications natively • Also runs on different CPU architecture (ARM vs. Intel) – Cocoa Touch Objective-C API for developing apps – Media services layer for graphics, audio, video – Core services provides cloud computing, databases – Core operating system, based on Mac OS X kernel
- 81. Android • Developed by Open Handset Alliance (mostly Google) – Open Source • Similar stack to IOS • Based on Linux kernel but modified – Provides process, memory, device-driver management – Adds power management • Runtime environment includes core set of libraries and Dalvik virtual machine – Apps developed in Java plus Android API • Java class files compiled to Java bytecode then translated to executable than runs in Dalvik VM • Libraries include frameworks for web browser (webkit), database (SQLite), multimedia, smaller libc
- 82. Android Architecture Applications Application Framework Android runtime Core Libraries Dalvik virtual machine Libraries Linux kernel SQLite openGL surface manager webkit libc media framework
- 83. Exam Questions 1. Define OS. 2. Write about Evolution of Operating Systems. 3. Explain basic Structure of a Computer System & also Explain its basic elements. 4. Discuss the basic components of a virtual computer. 5. What are OS Objectives? 6. What is an Operating System? Explain the functions of OS. 7. Discuss the various approaches of designing an operating system. 8. Write about Multitasking. 9. Explain the concept of Multiprogramming. Unit-I: Introduction 83
- 84. Exam Questions 10. What are the multi-tasking, multi-programming and multi- threading? 11. Explain the following: a. Multiprogramming b. Timesharing c. Virtual Memory 12. What are Distributed Operating Systems? 13. What are the types of real-time systems? 14. What is dispatcher? 15. What is a system call? Explain the categories of system calls. 16. What is a system program? Explain different types of system programs. |<< Unit-I: Introduction 84