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Operating System

Operating System. What is operating system?. An operating system (OS) is an integrated set of programs that controls the resources (the CPU, memory, I/O devices, etc) of a computer system and provides its users with an interface or virtual machine that is more convenient to use than ..machine.

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Operating System

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  1. Operating System www.AssignmentPoint.com

  2. What is operating system? • An operating system (OS) is an integrated set of programs that controls the resources (the CPU, memory, I/O devices, etc) of a computer system and provides its users with an interface or virtual machine that is more convenient to use than ..machine. • According to this definitions, the two primary objectives of an operating system are : • Making a computer system convenient to use • Managing the resources of a computer system www.AssignmentPoint.com

  3. Users Other system SW and applicationPrograms Operating System Computer Hardware Logical architecture of a computer system. The OS layer hides the details of the hardware from the programmer and provides the programmer with a convenient interface for using the system www.AssignmentPoint.com

  4. start the computer provide a user interface manage programs administer security control a network establish an Internet connection schedule jobs and configure devices monitor performance provide file management and other utilities What are the functions of an operating system? www.AssignmentPoint.com

  5. Main Functions of an Operating System • The main functions performed by most operating systems of today are as follows: • Process management • Memory Management • File Management • Security • Command Interpretation www.AssignmentPoint.com

  6. Step 1.The operating system transfers the least recently used data and program instructions to disk because RAM is needed for other functions. Step 2.The operating system transfers data and program instructions from hard disk to RAM when they are needed. Operating System Functions • What is memory management? • Optimizing use of random access memory (RAM) • With virtual memory (VM), portion of hard disk is allocated to function as RAM www.AssignmentPoint.com

  7. Adjusts schedule based on job’s priority Receiving data from input device Sending information to output device A job is operation the processor manages Processing instructions Transferring items between storage and memory Operating System Functions (cont..) • How does an operating system schedule jobs? www.AssignmentPoint.com

  8. Operating System Functions (cont…) • What is spooling? • Sending print jobs to buffer instead of directly to printer • Print jobs line up inqueue www.AssignmentPoint.com

  9. Operating System Functions (cont…) • How do you establish an Internet connection? • Windows XP includes New Connection Wizard • Guides user through setting up connection between computer and Internet www.AssignmentPoint.com

  10. Operating System Functions (cont…) • How does an operating system monitor performance? • Provides program, calledperformance monitor, that assesses and reports information about system resources and devices www.AssignmentPoint.com

  11. Operating System Functions (cont…) • What is a network operating system? • Allows users to share printer, Internet access, files, and programs on a network • Administers security by establishinguser nameandpasswordfor each user www.AssignmentPoint.com

  12. Measurement System Performance • The efficiency of an operating system and the overall performance of a computer system are usually measured in terms of the following: • Throughput • Turnaround time • Response time www.AssignmentPoint.com

  13. Process Management • A process (also called a job) is a program in execution. The main objective of the process management module of an OS is to manage the processes submitting to the system in such a manner to minimize the idle time of the various processors (CPU, I/O processors, etc) of the computer system. www.AssignmentPoint.com

  14. In a uniprogramming system, only one job is processed by the system at a time and all the system resources are exclusively available for the job unit it completes. • Multiprogramming is the name given to the interleaved execution of two or more different and independent programs by the same computer. • Multitasking is the concurrent execution of multiple jobs in a single-user system. www.AssignmentPoint.com

  15. The term multiprocessing is used to describe interconnected computer configurations, or computers with two or more CPUs, which have the ability to simultaneously execute several programs. In such a system, instructions from different and independent programs can be processed simultaneously execute different instructions from the same program. www.AssignmentPoint.com

  16. CPU – 1 Main memory CPU – 2 I/O processors I/O processors I/O units I/O units Basic organization of a typical multiprocessing system www.AssignmentPoint.com

  17. Difference between Multiprogramming and Multiprocessing • Multiprogramming is the interleaved execution of two or more processes by a single-CPU computer system. • On the other hand, multiprocessing is the simultaneously execution of two or more processes by a computer system having more than one CPU. To be more specific, multiprogramming involves execution a portion of one program, then a segment of another, etc. in brief consecutive periods. • Multiprocessing,however, makes it possible for the system to simultaneously work on several program segments of one or more programs. www.AssignmentPoint.com

  18. Advantages and limitations of Multiprocessing • Multiprocessing system typically have the following advantages: • Better Performance • Better Reliability • Multiprocessing systems,however, require a very sophisticated OS to schedule, balance, and coordinate the input, output, and processing activities of multiple processors. The design of such an OS is a complex and time taking job. Moreover, multiprocessing systems are expensive to procure and maintain. • In addition to the high charge paid initially, the regular operation and maintenance of these system is also a costly affair. www.AssignmentPoint.com

  19. Time-sharing • Time –sharingis a mechanism to provide simultaneous interactive use of a computer system by many users in such a way that each user is given the impression that he/she has his/her own computer. • It uses multiprogramming with a special CPU scheduling algorithm to achieve this. www.AssignmentPoint.com

  20. Requirements of Time-sharing systems • Time-sharing system typically require the following additional hardware and software features: • A number of terminals simultaneously connected to the system, so that multiple users can simultaneously use the system in interactive mode. • A relatively large memory to support multiprogramming. • Memory protection mechanism to prevent one job’s instructions and data from other jobs in a multiprogramming environment. www.AssignmentPoint.com

  21. Requirements of Time-sharing systems • Job status preservation mechanism to preserve a job’s complete status information when the CPU is taken away from it, and restoring this information back, before the CPU is given back to it again. • A special CPU scheduling algorithm, which allocates the CPU for a very short period one-by-one to each user process in a circular fashion. • An alarm clock mechanism to send an interrupt signal to the CPU after every time slice. www.AssignmentPoint.com

  22. Virtual Memory • What is virtual memory ? • Conferential memory management schemes, discussed until now, suffer from the following two main limitations: • A process cannot be loaded and has to keep waiting for its execution to start until sufficient free memory for loading the entire process becomes available. This may delay a process’s turnaround time. • A process cannot be loaded in a system whose main memory size is less than the total memory required by the process. www.AssignmentPoint.com

  23. Virtual Memory • Virtual memory is a memory management scheme, which overcomes the above-mentioned limitations by allowing the execution of processes that might not be completely loaded in the memory. • That is, it does not require an entire process to be in memory, before its execution can start. www.AssignmentPoint.com

  24. Advantages and Disadvantages of Virtual Memory • Advantages: • It provides a very large virtual memory to programmers on a system having smaller physical memory. That is, the logical memory size is no longer constrained by the physical memory size of the system. • It enables the execution of a process on a system whose main memory required by the process. • It enables a process’s execution to be standard even when sufficient free memory for loading the entire process is not available. This helps greatly improving the process’s turnaround time. This feature can also be effectively used to simultaneously accommodate program segments of a large number of users in the main memory. This increases the degree of multiprogramming resulting in increased CPU utilization and system throughput. www.AssignmentPoint.com

  25. Advantages and Disadvantages of Virtual Memory (cont..) 4. It makes programming task much easier, since the programmer no longer needs to worry about the size limitations of the physical memory available, but can concentrate, instead, on the problem to be programmed. www.AssignmentPoint.com

  26. Advantages and Disadvantages of Virtual Memory (cont..) • Disadvantages: • It is difficult to implement because it requires algorithms to support demand paging. • If used carelessly, it may substantially decrease performance instead of increasing performance. This happens when page-fault rate is very high for a process. That is, the process spend a more time in swapping out and swapping in of pages than in its execution. www.AssignmentPoint.com

  27. File Access Methods • To use the information stored in a file, it must be accessed and read into computer memory. • The two commonly supported file access methods at OS level are: • Sequential Access Files • Random Access Files. www.AssignmentPoint.com

  28. File Operations • An OS provides a set of operations to deal with files and their contents. • Create • Delete • Open • Close • Read • Write • Seek • Get attributes • Set attributes • Rename • Copy www.AssignmentPoint.com

  29. File Naming • When a file is created, it is given a name, which can be later used to access the file. • The rules for naming files vary from one OS to another. • For instance, consider the following examples: • MS-DOS • Some OS • Another OS www.AssignmentPoint.com

  30. Command Interpretation • The command Interpretation module (known as command interpreter) of an operating system serves as an interface for the user to communicate with the computer via it OS. • The two broad categories of user interfaces supported by various operating system • Command-line Interface • Graphical User Interface (GUI) www.AssignmentPoint.com

  31. Controls how you enter data and instructions and how information displays on screen command-line interface menu-driven interface What is a user interface? www.AssignmentPoint.com

  32. User interacts with menus and visual images such as icons and buttons What is a graphical user interface (GUI)? www.AssignmentPoint.com

  33. What is single user/ multitasking? • Working on two or more programs that reside in memory at same time • Foreground contains program you are using • Background contains programs that are running but are not in use www.AssignmentPoint.com

  34. Some Popular Operating System • Unix • MS-DOS • Microsoft Windows • Microsoft Windows NT • Linux www.AssignmentPoint.com

  35. Operating System Utility Programs www.AssignmentPoint.com

  36. Operating System Utility Programs • What is a utility program? • System software that performs maintenance-type tasks • Also called utility www.AssignmentPoint.com

  37. Operating System Utility Programs • What is a file manager? • Performs functions such as copying, renaming, deleting, and moving files • Image viewer displays contents of graphics file when you double click on it www.AssignmentPoint.com

  38. Operating System Utility Programs (cont..) • What is apersonal firewall? • Detects and protects a personal computer from unauthorized intrusions • The latest update to Windows XP automatically enables the built-in personal firewall upon installation www.AssignmentPoint.com

  39. Removes a program and all associated files In Windows XP, uninstaller is in Add/Remove Programs in Control Panel Operating System Utility Programs (cont..) • What is an uninstaller? www.AssignmentPoint.com

  40. Process of starting or restarting a computer • Cold bootTurning on computer that has been powered off • Warm bootRestarting computer that is powered on What is booting? www.AssignmentPoint.com

  41. What is a boot disk? • A floppy disk or CD that contains the OS files needed to boot your computer without using hard drive • Most manufacturers include arecovery CDfor restoring your system to original setup • The Windows XP Backup utility creates a set ofAutomated System Recovery disks www.AssignmentPoint.com Page 206

  42. What is a boot disk? www.AssignmentPoint.com Page 206

  43. Step 1.Power supply sends signal to com-ponents in system unit Step 4.Results of POST are compared with data in CMOS chip Step 5.BIOS looks for system files on a USB drive, in floppy disk drive or CD/DVD drive, and then hard disk Step 2.Processor accesses BIOS to start computer Step 6.Kernel (core) of operating system loads into RAM Step 3.BIOS runs tests, called the POST, to check components such as mouse, keyboard, and adapter cards Step 7.Operating system loads configuration information and displays desktop on screen How does a personal computer boot up? www.AssignmentPoint.com

  44. What is a disk scanner? • Detects and corrects problems on hard disk • Searches for and removes unnecessary files www.AssignmentPoint.com

  45. Reorganizes files and unused space on hard disk so programs run faster fragmented disk disk after defragmentation process What is a disk defragmenter? www.AssignmentPoint.com

  46. What is a diagnostic utility? • Compiles technical information about hardware and some software. • Prepares report outlining problems www.AssignmentPoint.com

  47. Operating System Utility Programs • What is a backup utility? • Copies selected files or entire hard disk onto another storage medium • Most compress files during backup to require less storage space www.AssignmentPoint.com

  48. Causes monitor’s screen to display moving image or blank screen if there is no activity for a specified time • To secure computer, user configures screen saver to require password to deactivate What is a screen saver? www.AssignmentPoint.com

  49. Embedded Network Stand-alone What are three categories of operating systems? www.AssignmentPoint.com

  50. Developed in early 1980s for personal computers D Used command-line interface when first developed, later included menus O Hardly used today because it does not offer GUI S Stand-Alone Operating Systems • What isDOS(Disk Operating System)? www.AssignmentPoint.com

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