CH07_OperatingSystems - Chapter 7 The Operating System Goal...

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Chapter 7: The Operating System Goal In this chapter we shift from hardware to software, starting with the most ubiquitous type of software in personal computers, servers, and workstations: the operating system (OS). The functions of the OS are briefly described and the most common OSs for PC are presented. After reading this chapter, the student should be able to compare OSs and describe their main uses. Functions of System Software The operating system ( OS ) or system software controls and coordinates the computer hardware. It acts as an intermediary between the hardware and application programs. Operating systems manage resources such as the CPU, disks, and memory; they manage input and output devices and communicate with the user via a user interface (Figure 1). Although there are computers that work without OSs, such as the computers in VCRs and microwave ovens, all computers that have general purposes need an OS. The OS is what makes the computer a tool that can be quickly changed to perform different functions. Without OSs, computers would be stuck with a single, hard-wired function. Computers that have OSs include PCs, laptops, workstations, servers, routers, wireless stations, handheld computers and PDAs, smart phones, and more. If the computer or device can accept and work with new hardware and software not originally included with it, then chances are it has an OS. Run and manage applications Interact with user (User Interface UI) Manage input/output Load and run device drivers Manage RAM Control CPU & manage its use Recognize and manage hardware Figure 1 . Main functions of an operaing system.
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7-2 Operating systems don't just manage the interaction of physical components. They also enable a computer to run two or more programs at once ( multitasking ), to run two or more parts of the same program at the same time ( multithreading ), or to run programs on more than one processor at once ( multiprocessing ). The OS must keep up with which programs are running, where they have been interrupted and should be restarted, and which programs and actions have priority, and still be ready to break in when the user asks for attention. Modern personal computers manage memory so that it is in effect limitless. Programs larger than the physical size of memory can still be run through the use of virtual memory . The page- swapping this requires is the responsibility of the OS. Although it consumes system resources and slows down operations, the use of virtual memory is absolutely required in order to multitask, because keeping even two programs running in memory at once usually requires at least some memory swapping. Input/output devices may require occasional attention to instruct them on their next set of operations and in between they will transfer data directly to or from memory, or may require constant attention for data to be transmitted and received. Device drivers are system software components that allow the OS to control a device. They are separate pieces of software, usually
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CH07_OperatingSystems - Chapter 7 The Operating System Goal...

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