Chapter02 Operating System Overview.ppt
- 1. 1 Operating System Overview Chapter 2 Prepared By: Shikha Manrai Shikha Manrai
- 2. 2 Operating System • A program that controls the execution of application programs • An interface between applications and hardware Shikha Manrai
- 3. 3 Operating System Objectives • Convenience – Makes the computer more convenient to use • Efficiency – Allows computer system resources to be used in an efficient manner • Ability to evolve – Permit effective development, testing, and introduction of new system functions without interfering with service Shikha Manrai
- 4. 4 Layers of Computer System Shikha Manrai
- 5. 5 Services Provided by the Operating System • Program development – Editors and debuggers • Program execution • Access to I/O devices • Controlled access to files • System access Shikha Manrai
- 6. 6 Services Provided by the Operating System • Error detection and response – Internal and external hardware errors • Memory error • Device failure – Software errors • Arithmetic overflow • Access forbidden memory locations – Operating system cannot grant request of application Shikha Manrai
- 7. 7 Services Provided by the Operating System • Accounting – Collect usage statistics – Monitor performance – Used to anticipate future enhancements – Used for billing purposes Shikha Manrai
- 8. 8 Operating System • Responsible for managing resources • Functions same way as ordinary computer software – It is program that is executed • Operating system relinquishes control of the processor Shikha Manrai
- 10. 10 Kernel • Portion of operating system that is in main memory • Contains most frequently used functions • Also called the nucleus Shikha Manrai
- 11. 11 Evolution of an Operating System • Hardware upgrades plus new types of hardware • New services • Fixes Shikha Manrai
- 12. 12 Evolution of Operating Systems • Serial Processing – No operating system – Machines run from a console with display lights, toggle switches, input device, and printer – Schedule time – Setup included loading the compiler, source program, saving compiled program, and loading and linking Shikha Manrai
- 13. 13 Evolution of Operating Systems • Simple Batch Systems – Monitors • Software that controls the sequence of events • Batch jobs together • Program branches back to monitor when finished Shikha Manrai
- 14. 14 Job Control Language (JCL) • Special type of programming language • Provides instruction to the monitor – What compiler to use – What data to use Shikha Manrai
- 15. 15 Hardware Features • Memory protection – Do not allow the memory area containing the monitor to be altered • Timer – Prevents a job from monopolizing the system Shikha Manrai
- 16. 16 Hardware Features • Privileged instructions – Certain machine level instructions can only be executed by the monitor • Interrupts – Early computer models did not have this capability Shikha Manrai
- 17. 17 Memory Protection • User program executes in user mode – Certain instructions may not be executed • Monitor executes in system mode – Kernel mode – Privileged instructions are executed – Protected areas of memory may be accessed Shikha Manrai
- 18. 18 I/O Devices Slow Shikha Manrai
- 19. 19 Uniprogramming • Processor must wait for I/O instruction to complete before preceding Shikha Manrai
- 20. 20 Multiprogramming • When one job needs to wait for I/O, the processor can switch to the other job Shikha Manrai
- 24. 24 Time Sharing • Using multiprogramming to handle multiple interactive jobs • Processor’s time is shared among multiple users • Multiple users simultaneously access the system through terminals Shikha Manrai
- 25. 25 Compatible Time-Sharing System (CTSS) • First time-sharing system developed at MIT Shikha Manrai
- 26. 26 Major Achievements • Processes • Memory Management • Information protection and security • Scheduling and resource management • System structure Shikha Manrai
- 27. 27 Processes • A program in execution • An instance of a program running on a computer • The entity that can be assigned to and executed on a processor • A unit of activity characterized by a single sequential thread of execution, a current state, and an associated set of system resources Shikha Manrai
- 28. 28 Difficulties with Designing System Software • Improper synchronization – Ensure a process waiting for an I/O device receives the signal • Failed mutual exclusion • Nondeterminate program operation – Program should only depend on input to it, not on the activities of other programs • Deadlocks Shikha Manrai
- 29. 29 Process • Consists of three components – An executable program – Associated data needed by the program – Execution context of the program • All information the operating system needs to manage the process Shikha Manrai
- 31. 31 Memory Management • Process isolation • Automatic allocation and management • Support of modular programming • Protection and access control • Long-term storage Shikha Manrai
- 32. 32 Virtual Memory • Allows programmers to address memory from a logical point of view • No hiatus between the execution of successive processes while one process was written out to secondary store and the successor proceess was read in Shikha Manrai
- 33. 33 Virtual Memory and File System • Implements long-term store • Information stored in named objects called files Shikha Manrai
- 34. 34 Paging • Allows process to be comprised of a number of fixed-size blocks, called pages • Virtual address is a page number and an offset within the page • Each page may be located any where in main memory • Real address or physical address in main memory Shikha Manrai
- 36. 36 Virtual Memory Addressing Shikha Manrai
- 37. 37 Information Protection and Security • Availability – Concerned with protecting the system against interruption • Confidentiality – Assuring that users cannot read data for which access is unauthorized Shikha Manrai
- 38. 38 Information Protection and Security • Data integrity – Protection of data from unauthorized modification • Authenticity – Concerned with the proper verification of the identity of users and the validity of messages or data Shikha Manrai
- 39. 39 Scheduling and Resource Management • Fairness – Give equal and fair access to resources • Differential responsiveness – Discriminate among different classes of jobs • Efficiency – Maximize throughput, minimize response time, and accommodate as many uses as possible Shikha Manrai
- 40. 40 Key Elements of Operating System Shikha Manrai
- 41. 41 System Structure • View the system as a series of levels • Each level performs a related subset of functions • Each level relies on the next lower level to perform more primitive functions • This decomposes a problem into a number of more manageable subproblems Shikha Manrai
- 42. 42 Process Hardware Levels • Level 1 – Electronic circuits – Objects are registers, memory cells, and logic gates – Operations are clearing a register or reading a memory location • Level 2 – Processor’s instruction set – Operations such as add, subtract, load, and store Shikha Manrai
- 43. 43 Process Hardware Levels • Level 3 – Adds the concept of a procedure or subroutine, plus call/return operations • Level 4 – Interrupts Shikha Manrai
- 44. 44 Concepts with Multiprogramming • Level 5 – Process as a program in execution – Suspend and resume processes • Level 6 – Secondary storage devices – Transfer of blocks of data • Level 7 – Creates logical address space for processes – Organizes virtual address space into blocks Shikha Manrai
- 45. 45 Deal with External Objects • Level 8 – Communication of information and messages between processes • Level 9 – Supports long-term storage of named files • Level 10 – Provides access to external devices using standardized interfaces Shikha Manrai
- 46. 46 Deal with External Objects • Level 11 – Responsible for maintaining the association between the external and internal identifiers • Level 12 – Provides full-featured facility for the support of processes • Level 13 – Provides an interface to the operating system for the user Shikha Manrai
- 47. 47 Modern Operating Systems • Microkernel architecture – Assigns only a few essential functions to the kernel • Address spaces • Interprocess communication (IPC) • Basic scheduling Shikha Manrai
- 48. 48 Modern Operating Systems • Multithreading – Process is divided into threads that can run concurrently • Thread – Dispatchable unit of work – executes sequentially and is interruptable • Process is a collection of one or more threads Shikha Manrai
- 49. 49 Modern Operating Systems • Symmetric multiprocessing (SMP) – There are multiple processors – These processors share same main memory and I/O facilities – All processors can perform the same functions Shikha Manrai
- 51. 51 Modern Operating Systems • Distributed operating systems – Provides the illusion of a single main memory space and single secondary memory space Shikha Manrai
- 52. 52 Modern Operating Systems • Object-oriented design – Used for adding modular extensions to a small kernel – Enables programmers to customize an operating system without disrupting system integrity Shikha Manrai
- 53. 53 Windows Architecture • Modular structure for flexibility • Executes on a variety of hardware platforms • Supports application written for other operating system Shikha Manrai
- 54. 54 Shikha Manrai
- 55. 55 Operating System Organization • Modified microkernel architecture – Not a pure microkernel – Many system functions outside of the microkernel run in kernel mode • Any module can be removed, upgraded, or replaced without rewriting the entire system Shikha Manrai
- 56. 56 Kernel-Mode Components • Executive – Contains base operating system services • Memory management • Process and thread management • Security • I/O • Interprocess communication • Kernel – Consists of the most used components Shikha Manrai
- 57. 57 Kernel-Mode Components • Hardware abstraction layer (HAL) – Isolates the operating system from platform-specific hardware differences • Device drivers – Translate user I/O function calls into specific hardware device I/O requests • Windowing and graphics systems – Implements the graphical user interface (GUI) Shikha Manrai
- 58. 58 Windows Executive • I/O manager • Cache manager • Object manager • Plug and play manager • Power manager • Security reference monitor • Virtual memory manager • Process/thread manager • Configuration manager • Local procedure call (LPC) facility Shikha Manrai
- 59. 59 User-Mode Processes • Special system support processes – Ex: logon process and the session manager • Service processes • Environment subsystems • User applications Shikha Manrai
- 60. 60 Client/Server Model • Simplifies the Executive – Possible to construct a variety of APIs • Improves reliability – Each service runs on a separate process with its own partition of memory – Clients cannot not directly access hardware • Provides a uniform means for applications to communicate via LPC • Provides base for distributed computing Shikha Manrai
- 61. 61 Threads and SMP • Operating system routines can run on any available processor • Different routines can execute simultaneously on different processors • Multiple threads of execution within a single process may execute on different processors simultaneously • Server processes may use multiple threads • Share data and resources between process Shikha Manrai
- 62. 62 Windows Objects • Encapsulation – Object consists of one or more data items and one or more procedures • Object class or instance – Create specified instances of an object • Inheritance – Support to some extent in the Executive • Polymorphism Shikha Manrai
- 63. 63 UNIX • Hardware is surrounded by the operating system software • Operating system is called the system kernel • Comes with a number of user services and interfaces – Shell – Components of the C compiler Shikha Manrai
- 66. 66 Modern UNIX Kernel Shikha Manrai
- 67. 67 Modern UNIX Systems • System V Release 4 (SVR4) • Solaris 9 • 4.4BSD • Linux Shikha Manrai