Modern Operating Systems
نویسنده
چکیده
ion is the key to managing complexity. Good abstractions turn a nearly impossible task into two manageable ones. The first one of these is defining and^aglementing the abstractions. The second one is using these abstractions to sol^He problem at hand. One abstraction that almost every computer user understands is the file. It is a useful piece of information, such as a digital photo, SEC. 1.1 WHAT IS AN OPERATING SYSTEM? 5 saved e-mail message, or Web page. Dealing with photos, e-mails, and Web pages is easier than the details of disks, such as the floppy disk described above. The job of the operating system is to create good abstractions and then implement and manage the abstract objects thus created. In this book, we will talk a lot about abstractions. They are one of the keys to understanding operating systems. This point is so important that it is worth repeating in different words. With all due respect to the industrial engineers who designed the Macintosh, hardware is ugly. Real processors, memories, disks, and other devices are very complicated and present difficult, awkward, idiosyncratic, and inconsistent interfaces to the people who have to write software to use them. Sometimes this is due to the need for backward compatibility with older hardware, sometimes due to a desire to save money, but sometimes the hardware designers do not realize (or care) how much trouble they are causing for the software. One of the major tasks of the operating system is to hide the hardware and present programs (and their programmers) with nice, clean, elegant, consistent, abstractions to work with instead. Operating systems turn the ugly into the beautiful, as shown in Fig. 1-2. Application programs
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تاریخ انتشار 1992