Operating system overview by narender singh sandhu
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- 2. Presented by Narender Singh Sandhu 2
- 3. A program that controls the execution of application programs An interface between applications and hardware 3
- 4. 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 4
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- 6. Program development ◦ Editors and debuggers Program execution Access to I/O devices Controlled access to files System access 6
- 7. 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 7
- 8. Accounting ◦ Collect usage statistics ◦ Monitor performance ◦ Used to anticipate future enhancements ◦ Used for billing purposes 8
- 9. Responsible for managing resources Functions same way as ordinary computer software ◦ It is program that is executed Operating system relinquishes control of the processor 9
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- 11. Portion of operating system that is in main memory Contains most frequently used functions Also called the nucleus 11
- 12. Hardware upgrades plus new types of hardware New services Fixes 12
- 13. 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 13
- 14. Simple Batch Systems ◦ Monitors Software that controls the sequence of events Batch jobs together Program branches back to monitor when finished 14
- 15. Special type of programming language Provides instruction to the monitor ◦ What compiler to use ◦ What data to use 15
- 16. Memory protection ◦ Do not allow the memory area containing the monitor to be altered Timer ◦ Prevents a job from monopolizing the system 16
- 17. Privileged instructions ◦ Certain machine level instructions can only be executed by the monitor Interrupts ◦ Early computer models did not have this capability 17
- 18. 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 18
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- 20. Processor must wait for I/O instruction to complete before preceding 20
- 21. When one job needs to wait for I/O, the processor can switch to the other job 21
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- 25. Using multiprogramming to handle multiple interactive jobs Processor’s time is shared among multiple users Multiple users simultaneously access the system through terminals 25
- 26. First time-sharing system developed at MIT 26
- 27. Processes Memory Management Information protection and security Scheduling and resource management System structure 27
- 28. 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 28
- 29. 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 29
- 30. 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 30
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- 32. Process isolation Automatic allocation and management Support of modular programming Protection and access control Long-term storage 32
- 33. 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 33
- 34. Implements long-term store Information stored in named objects called files 34
- 35. 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 35
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- 38. Availability ◦ Concerned with protecting the system against interruption Confidentiality ◦ Assuring that users cannot read data for which access is unauthorized 38
- 39. 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 39
- 40. 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 40
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- 42. 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 42
- 43. 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 43
- 44. Level 3 ◦ Adds the concept of a procedure or subroutine, plus call/return operations Level 4 ◦ Interrupts 44
- 45. 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 45
- 46. 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 46
- 47. 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 47
- 48. Microkernel architecture ◦ Assigns only a few essential functions to the kernel Address spaces Interprocess communication (IPC) Basic scheduling 48
- 49. 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 49
- 50. Symmetric multiprocessing (SMP) ◦ There are multiple processors ◦ These processors share same main memory and I/O facilities ◦ All processors can perform the same functions 50
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- 52. Distributed operating systems ◦ Provides the illusion of a single main memory space and single secondary memory space 52
- 53. Object-oriented design ◦ Used for adding modular extensions to a small kernel ◦ Enables programmers to customize an operating system without disrupting system integrity 53
- 54. Modular structure for flexibility Executes on a variety of hardware platforms Supports application written for other operating system 54
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- 56. 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 56
- 57. Executive ◦ Contains base operating system services Memory management Process and thread management Security I/O Interprocess communication Kernel ◦ Consists of the most used components 57
- 58. 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) 58
- 59. 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 59
- 60. Special system support processes ◦ Ex: logon process and the session manager Service processes Environment subsystems User applications 60
- 61. 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 61
- 62. 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 62
- 63. 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 63
- 64. 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 64
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- 68. System V Release 4 (SVR4) Solaris 9 4.4BSD Linux 68
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