Unit 1 Operating System

Unit 1 Operating System Microsoft isn’t evil; they just make really crappy operating system. — Linus Torvalds, the creator of Linux Every operating system out there is about equal…We all suck. — Brian Valentine, Microsoft senior vice president, describing the state of the art in OS security, 2003 Advanced English Reading and Writing 2 高级英语读写教程 2 OPERATING SYSTEM is an integral part of virtually every computer system. It fundamentally affects how you can use your computer. Can you run two programs at the same time? Can you connect your computer to a network? Does your computer run dependably? Does all your software have a similar look and feel, or Preview do you have to learn a different set of controls and commands for each new program you acquire? To answer questions like these, it is helpful to have a clear idea about what an operating system is and what it does. Section A Pre-reading Activities 1. Choose the proper word from the box below to describe each picture. A. Microsoft Windows B. Chrome OS C. Linux D. DOS E. OpenSolaris F. Mac OS G. UNIX 1）( ) 2）( ) 3）( ) 4）( ) 2 Unit 1 Operating System 2. What is in common among the pictures above? 3. Do you know what an operating system is, according to what you have learned? 4. What does an operating system do? Text A Operating System Activities 1. What is an operating system? An operating system (abbreviated OS) is a type of system software that acts as the master controller1 for all activities that take place within a computer system. It is one of the factors that determine your computer’s compatibility and platform. Most personal computers are sold with a preinstalled operating system, such as Microsoft Windows or Mac OS. A third operating system called Linux is typically used for high-end workstations and servers, but can also be installed on personal computers. A variety of other operating systems, such as Google Chrome OS2, DOS, UNIX3, and OpenSolaris4 are also available. 2. Is the Windows operating system the same as Windows software? No. Although it is true that an operating system is software, terms such as “Windows software”, “Mac software”, or “Linux software” are used to refer to application software5. Windows software, for example, refers to applications designed to run on computers that have Microsoft Windows installed as the operating system. A program called Microsoft Word for Windows is an example of Windows software; it is a word processing program designed to run under the Windows operating system. Mac software is designed to run under Mac OS, and Linux software is designed to run under the Linux operating system. 3. What does an operating system do? The most obvious responsibility of your computer’s operating system is to provide an environment for running software and controlling peripheral devices6. 4. Your computer’s operating system, application software, and device drivers7 are organized similar to the chain of command in an army. You issue a command using application software. Application software tells the operating system what to do. The operating system tells the device drivers, the device drivers tell the hardware, and the hardware actually does the work. For example, a command to print a document is relayed through various levels of software, including the operating system, until it reaches the printer. The following picture illustrates this chain of command for printing a document or photo. 3 Advanced English Reading and Writing 2 高级英语读写教程 2 2. The word processing application signals the operating system that a document must be sent Printer Driver to the printer. 4. The device driver controls the printer as it prints the document. 1. You issue the Print command while using 3. The operating system application software, communicates the such as a word processor. document data to the device driver for the printer. 5. The operating system interacts with application software, device drivers, and hardware to manage a computer’s resources. In the context of a computer system, the term “resource” refers to any component that is required to perform work. For example, the processor is a computer’s main resource. RAM8 (Random Access Memory), storage space, and peripherals are also resources. While you interact with application software, your computer’s operating system is busy behind the scenes with resource management tasks9 such as: keep track of storage resources, ensure that input and output proceed in an orderly manner and establish basic elements of the user interface such as the appearance of the desktop, menu, and toolbars. 6. How do operating systems manage processor resources? Every cycle of a computer’s microprocessor is a resource for accomplishing tasks. Many activities—called processes—compete for the attention of your computer’s microprocessor. Commands are arriving from programs you’re using, while input is arriving from the keyboard and mouse. At the same time, data must be sent to the display device or printer, and web pages are arriving from your Internet connection. 7. To manage all these competing processes, your computer’s operating system must ensure that each process receives its share of microprocessor cycles10. When using Windows, you can open the Task Manager11 to see a list of processes that are being executed by the microprocessor. 4 Unit 1 Operating System 8. The Windows operating system displays a list of processes when you hold down the Ctrl, Alt, and Del keys. Most processes are legitimate programs that run in the background to carry out tasks for the operating system, device drivers, and applications. Occasionally a bot or worm will launch rogue processes. If you want to know if a process is legitimate, you can google it. 9. How do operating systems handle so many processes? During a typical computing session12, your computer might run an average of 50 processes. Ideally, the operating system should be able to help the microprocessor switch seamlessly from one process to another. Depending on the capabilities of the operating system and computer hardware, processes can be managed by multitasking13, multithreading14, and multiprocessing15. 10. Multitasking provides process and memory management services that allow two or more tasks, jobs, or programs to run simultaneously. Most of today’s operating systems, including the OS on your personal computer, offer multitasking services. 11. Within a single program, multithreading allows multiple parts, or threads, to run simultaneously. For example, one thread for a spreadsheet program might be waiting for input from the user while other threads perform a long calculation in the background. Multithreading can speed up performance on single or multiple processor computers. 12. Many new computers include multi-core processors16 or multiple processors. An operating system’s multiprocessing capability supports a division of labor among all the processing units17. 13. How does an operating system manage memory? A microprocessor works with data and executes instructions stored in RAM—one of your computer’s most important resources. When you want to run more than one program at a time, the operating system has to allocate specific areas of memory for each program. 14. Sometimes an application requests memory, but never releases it—a condition called a memory leak18. Memory leaks away into this application’s reserved area, eventually preventing other programs from accessing enough memory to function properly. Those programs can crash, and the operating system might display error messages, such as “General Protection Fault” or “Program Not Responding”. Your PC can sometimes recover from a memory leak if you access Task Manager to close the corrupted program. 15. How does the OS keep track of storage resources? Behind the scenes, an operating system acts as a filing clerk that stores and retrieves files from your computer’s hard drive and other storage devices. It remembers the names and locations of all your files and keeps track of empty spaces where new files can be stored. 16. Why does the operating system get involved with peripheral devices? Every device connected to a computer is regarded as an input or output resource. Your computer’s operating system communicates with device driver software so that data can travel smoothly between the 5 Advanced English Reading and Writing 2 高级英语读写教程 2 computer and peripheral resources. If a peripheral device or driver is not performing correctly, the operating system makes a decision about what to do—usually it displays an on-screen message to warn you of the problem. 17. Your computer’s operating system ensures that input and output proceed in an orderly manner, using buffers to collect and hold data while the computer is busy with other tasks. By using a keyboard buffer, for example, your computer never misses one of your keystrokes, regardless of how fast you type or what else is happening in your computer at the same time. 18. Are different operating systems needed for different computing tasks? One operating system might be better suited to some computing tasks than others. To provide clues to their strengths and weaknesses, operating systems are informally categorized and characterized using one or more of the following terms: 19. A single-user operating system expects to deal with one set of input devices—those that can be controlled by one user at a time. Operating systems for handheld computers19 and some personal computers fit into the single-user category. DOS is an example of a single-user operating system. 20. A multiuser operating system allows a single, centralized computer to deal with simultaneous input, output, and processing requests from many users. One of its most difficult responsibilities is to schedule all the processing requests that a centralized computer must perform.

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