Introduction to Operating systems & RTOS

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Introduction to Operating systems & RTOS

  1. 1. Introduction to Operating systems & RTOS Dr. Y.NARASIMHA MURTHY. Ph. D Department of Electronics Sri Sai baba National College (Autonomous) Anantapur-515001(A.P)-India
  2. 2. Invocation…. Where the mind is without fear and the head is held high; Where knowledge is free; Where the world has not been broken up into fragments by narrow domestic walls; Where words come out from the depth of truth; Where tireless striving stretches its arms towards perfection; Where the clear stream of reason has not lost its way into the dreary desert sand of dead habit; Where the mind is led forward by thee into ever-widening thought and action--- Into that heaven of freedom, my Father, let my country awake. ---------RABINDRANATH TAGORE
  3. 3. Prologue … A computer is a complex system with many resources like CPU, I/O devices, disk, memory etc… For any common user it is always a confusion about the using of the resources effectively. Because, unless otherwise the system is user-friendly, the user cannot use the computers effectively.
  4. 4. <ul><li>So we always require a system software which can take care of all the hardware complexities and shoulder the responsibility of resource allocation such that the user can work with the computer more effectively. This was realised by the people very long back and they tried to develop a software to shield the programmers from the complexity of the hardware. </li></ul>
  5. 5. The result is, a layer of software on the top of the hardware, to manage all parts of the system and present the user with an interface or “Virtual machine” that is easier to understand the program. This layer of the software has become our so-called OPERATING SYSTEM .
  6. 6. Now Lets answer the question What is an Operating System?
  7. 7. A more formal definition! OS is “ A collection of software modules to assist programmers in enhancing the system efficiency , flexibility and robustness. Or “ Operating system is a piece of software which controls all the computer’s resources and provides the base upon which the application programs can be written”
  8. 8. From the user point of view OS is “ An extended machine (virtual)” and From the systems view point “ It is a resource manager”.
  9. 9. Let us substantiate ! <ul><li>The operating system shields the programmer from the disk hardware and provides a simple file oriented interface. It also conceals a lot of unpleasant business concerning interrupts, timers, memory management and other low level features. So the function of the OS is to present the user with the equivalent of an extended machine or virtual machine. </li></ul>
  10. 10. <ul><li>Contd…… </li></ul><ul><li>A computer is provided with processors, memories, timers, disks, terminals, drives, printers, network interfaces and a wide variety of the other devices. The operating system provides an orderly and controlled allocation of the processors, memories and I/O devices among the various programs competing for them. It also keep track of, who is using which resource, to grant resource requests, to account for usage and to mediate conflicting requests from different users and programs. </li></ul>
  11. 11. Contd…. <ul><li>Provides an environment in which programs can be executed. Makes efficient use of computer hardware and peripherals. Hide the peculiarities of the disks and other I/O devices.Hence the OS is also treated as a resource manager </li></ul>
  12. 12. So,Where your OS sits in your System? compilers databases word processors CPU memory I/O devices
  13. 13. Evolution of OS <ul><li>The next slide shows the evolution of OS . </li></ul><ul><li>Actually Prof.E.W.Dijsktra is considered as the father of Operating system. </li></ul>
  14. 14. More advanced Distributed O/S Network O/S 1990 KBCS (Knowledge based computer system) Fifth User friendly. He need not know about computer MS-DOS UNIX 1980-90 IBM 360 Fourth Spooling (On-line) Multiprogramming Time sharing O/S (many at the same time PDP-II 1965-80 IBM 360 Third Paper tape Punched cards Offline printing Batch O/S (Not interact system) 1955-65 IBM 1401, 7094 Second Plug in boards Jumper wired No O/S 1945-55 Vacuum tubes ENIAC EDVAC Analog computers First Feature O/S used Era Generation
  15. 15. The basic requirements of OS: <ul><li>Usability (Robustness) </li></ul><ul><li>OS should accept all valid inputs ,even with errors and gracefully handle all invalid inputs .It should not be crashed under any circumstances ,and could be recovered,even we remove any hardware while they are running . </li></ul>
  16. 16. <ul><li>It should provide every facility for the efficient </li></ul><ul><li>development of application software and should </li></ul><ul><li>not leave out any part of the facility. </li></ul><ul><li>Adaptability : </li></ul><ul><li>Should support necessary activities,and not to impose unnecessary restrictions.Adapt as needs and resources change. </li></ul>Facilities:
  17. 17. Cost: Low maintenance cost and the system should not require constant attention.Efficient service and good algorithms must be provided at low cost
  18. 18. OS Components <ul><li>Kernel: Core components of the OS </li></ul><ul><li>Process scheduler : </li></ul><ul><ul><li>Determines when and for long each process executes </li></ul></ul><ul><li>Memory manager : </li></ul><ul><ul><li>Determines when and how memory is allocated to processes </li></ul></ul><ul><ul><li>Decides what to do when main memory is full </li></ul></ul><ul><li>File system : </li></ul><ul><ul><li>Organizes named collections of data in persistent storage </li></ul></ul><ul><li>Networking : </li></ul><ul><ul><li>Enables processes to communicate with one another </li></ul></ul>
  19. 19. The primary functions of an operating system <ul><li>Multiplexing the processor(s) </li></ul><ul><li>Scheduling the processes </li></ul><ul><li>Coordinating interaction among processes,interprocess communication and Synchronization. </li></ul><ul><li>Managing the system resources(I/O,memory,data files) </li></ul><ul><li>Enforcing acess control and protection </li></ul><ul><li>Maintaining the system integrity and performing error recovery </li></ul><ul><li>Providing an interface to the users </li></ul>
  20. 20. TYPES OF OPERATING SYSTEMS <ul><li>There are three types of Operating systems based on their application </li></ul><ul><li>Stand-Alone Operating system </li></ul><ul><li>Network Operating systems </li></ul><ul><li>Embedded Operating systems </li></ul>
  21. 21. Stand-Alone Operating system <ul><li>It is a complete operating system that works </li></ul><ul><li>on a desktop or notebook computer. </li></ul><ul><li>Examples of stand-alone operating systems are: </li></ul><ul><li>DOS </li></ul><ul><li>Windows 2000 professional </li></ul><ul><li>Mac OS X </li></ul>
  22. 22. Network Operating systems <ul><li>It is an operating system that provides extensive support for computer networks. A network operating system typically resides on a server. </li></ul><ul><li>Examples of a network Operating system are: </li></ul><ul><li>Windows 2000 server </li></ul><ul><li>Unix </li></ul><ul><li>Linux </li></ul><ul><li>Solaris </li></ul>
  23. 23. Embedded Operating system <ul><li>You can find this operating system on handheld computers and small devices. It resides on a ROM chip. Examples of embedded operating systems are : </li></ul><ul><li>Windows CE </li></ul><ul><li>Pocket PC 2002 </li></ul><ul><li>Palm OS </li></ul>
  24. 24. Now Lets see various Operating systems and their features
  25. 58. Operating systems market share 81.94% 4.52% 4.00% 3.52% 2.48% 1.14% 0.71% 0.66% 0.59% 0.17% 0.20% Windows XP Windows Vista Windows 2000 Mac OS MacIntel Windows 98 Linux Windows NT Windows Me Ninendo Wii Other 1 2 3 4 5 6 7 8 9 10 11 Market share Operating system S.No
  26. 59. REAL- TIME OPERATING SYSTEM (RTOS) : <ul><li>“ The ability of the operating system to provide a required level of service in a bounded response time”. </li></ul><ul><li>Or </li></ul><ul><li>The Real time operating system is an operating system that make it suitable for building real time computing applications also known as real time systems(RTS). </li></ul>
  27. 60. What is a real time system(RTS)? <ul><li>A RTS is a system where correctness of computing depends not only on the correctness of the logical result of the computation but also on the result of delivery time. In a well designed RTS each individual dead line should be met.But in practice it is not possible and also costly to achieve this requirement.So, people classified the real time systems in to the following types. </li></ul>
  28. 61. Hard Real time : <ul><li>Here missing an individual deadline results in catastrophic failure of the system which also causes a great financial loss . </li></ul><ul><li>The examples for Hard real time systems are : </li></ul><ul><li>Air traffic control </li></ul><ul><li>Nuclear power plant control </li></ul>
  29. 62. Firm Real time <ul><li>In this, missing a deadline results in unacceptable quality reduction. Technically there is no difference with hard Real time, but economically the disaster risk is limited. </li></ul><ul><li>Examples for Firm real time are : </li></ul><ul><li>Failure of Ignition of a automobile </li></ul><ul><li>Failure of opening of a safe </li></ul>
  30. 63. Soft real time : <ul><li>Here the dead line may not be fulfilled and can be recovered from. The reduction in system quality and performance is at an acceptable level. </li></ul><ul><li>Examples of Soft real time systems : </li></ul><ul><li>Multimedia transmission and reception </li></ul><ul><li>Networking, telecom (Mobile) networks </li></ul><ul><li>websites and services </li></ul><ul><li>Computer games </li></ul>
  31. 64. Components of an RTOS <ul><li>Process (task) management </li></ul><ul><ul><li>Scheduler </li></ul></ul><ul><ul><li>Synchronization mechanism </li></ul></ul><ul><ul><ul><li>Interprocess communication (IPC) </li></ul></ul></ul><ul><ul><ul><li>Semaphores </li></ul></ul></ul><ul><li>Memory management </li></ul><ul><li>Interrupt service mechanism </li></ul><ul><li>I/O management , H.A.Layer </li></ul><ul><li>Development Environments </li></ul><ul><li>Communication subsystems (Option) </li></ul><ul><li>Board Support Packages (BSP) </li></ul>
  32. 65. Features of RTOS’s <ul><li>Predictability </li></ul><ul><li>Timeliness </li></ul><ul><li>Reliability </li></ul><ul><li>Fault tolerant </li></ul><ul><li>Efficiency of System Components </li></ul><ul><li>Resource Allocation. </li></ul><ul><li>Interrupt Handling. </li></ul><ul><li>Other issues like kernel size. </li></ul>
  33. 66. Types of RTOS <ul><li>Commercial RTOSs </li></ul><ul><li>VxWorks </li></ul><ul><li>QNX </li></ul><ul><li>MicroC/OS-II </li></ul><ul><li>RTLinux </li></ul><ul><li>Windows CE ( www.microsoft.com) </li></ul>
  34. 67. VxWorks <ul><li>This is from Wind River ( www.windriver.com ). </li></ul><ul><li>One of the most popular real time operating system </li></ul><ul><li>This has been used in the Mars pathfinder </li></ul><ul><li>It supports a number of processors including Power Pc, Intel strong ARM,ARM,Hitachi SuperH, Motorola ColdFire etc… </li></ul><ul><li>It supports multiple scheduling algorithm and also priority inheritance </li></ul>
  35. 68. QNX Neutrino <ul><li>It is a popular real time operating system from QNX software systems limited (www. qnx.com) </li></ul><ul><li>It supports a number of Processors namely ARM,MIPS,Power PC,SH-4,X86 &Pentium… </li></ul><ul><li>It has support for C,C++ and Java languages and TCP/IP protocol stack. </li></ul><ul><li>This supports multiple scheduling algorithms and up to 65,535 tasks. My SQL can be integrated with this OS to create embedded database applications. </li></ul><ul><li>Even small embedded systems can use this OS as it requires 64K Kernel ROM and 32K kernel RAM </li></ul>
  36. 69. MicroC/OS-II <ul><li>Microcontroller operating system version –II is developed by Jean J.Labrosse( www.ucos-II.com)is a preemptive real-time operating system which is popular in academic institutions for teaching RTOS concepts. </li></ul><ul><li>It can support only 64 tasks out of which eight are system tasks </li></ul><ul><li>Round-robin scheduling algorithm is not supported by this OS </li></ul>
  37. 70. RTLinux <ul><li>This OS was developed by FSM Labs( www.fsmlabs.com ) and available in two versions RTLinux Pro and RTLinuxFree. </li></ul><ul><li>The RTLinux Pro is the priced edition and RTLinux Free is the free open source release. </li></ul><ul><li>RTLinux is a hard real-time operating system with support for many processors such as x86,Pentium,PowerPC,ARM,Fujitsu,MIPS and Alpha </li></ul><ul><li>It does not support priority inheritance. </li></ul>
  38. 71. Windows CE <ul><li>Windows CE (also known officially as Windows Embedded Compact and sometimes abbreviated WinCE) is an operating system developed by Microsoft for minimalistic computers and embedded systems. </li></ul><ul><li>Windows CE is optimized for devices that have minimal storage—a Windows CE kernel may run in under a megabyte of memory </li></ul>
  39. 72. <ul><li>The system supports 256 priority levels and uses priority inheritance for dealing with priority inversion. The fundamental unit of execution is the thread. This helps to simplify the interface and improve execution time. </li></ul><ul><li>A distinctive feature of Windows CE compared to other Microsoft operating systems is that large parts of it are offered in source code form. </li></ul>
  40. 73. Programming languages Used <ul><li>C is most widely used in RTOS programming </li></ul><ul><li>C++ and Ada are the next more popular for large projects. </li></ul><ul><li>Assembly languages for increasing efficiency and reusing the previous code </li></ul><ul><li>Java may also be a choice for some applications </li></ul>
  41. 74. Which is the Best? <ul><li>It is always very difficult to judge which RTOS is the best and which is the worst.It depends on the application and interests of the user. Among the above, Linux is royalty free but it has serious drawbacks if it comes to real-time behavior. The VxWorks is a very old and stable RTOS. Similarly Windows CE 5.0 version RTOS is a robust and stable regarding the real-time behavior. </li></ul>
  42. 75. REFERENCES <ul><li>Modern Operating Sytems- Andrew S. Tanenbaum (PHI) </li></ul><ul><li>Operating Systems –W. Stallings (PHI) </li></ul><ul><li>Operating system Concepts-Avi Silberschatz & Peter Baer Galvin. </li></ul><ul><li>Operating Systems-D. M. Dhamdhere- TMH </li></ul>
  43. 76. THANQ

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