2--x86 Processor

Such access is reserved for the operating system

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Unformatted text preview: of device was installed, and you would For More BS-IT Books, Notes & Assignments visit: www.bsit.zxq.net 2.6 Chapter Summary Downloaded From: www.bsit.zxq.net 55 not be concerned with nonstandard features the card might have. At the BIOS level, you would query the sound card (using its installed device driver software) and find out whether it belonged to a certain class of sound cards having known features. At the hardware level, you would fine tune the program for certain models of audio cards, taking advantage of each card’s special features. Finally, not all operating systems permit user programs to directly access system hardware. Such access is reserved for the operating system itself and specialized device driver programs. This is the case with all versions of Microsoft Windows beyond Windows 95, in which vital system resources are shielded from application programs. MS-DOS, on the other hand, has no such restrictions. 2.5.2 Section Review 1. Of the four levels of input/output in a computer system, which is the most universal and portable? 2. What characteristics distinguish BIOS-level input/output? 3. Why are device drivers necessary, given that the BIOS already has code that communicates with the computer’s hardware? 4. In the example regarding displaying a string of characters, which level exists between the operating system and the video controller card? 5. At which level(s) can an assembly language program manipulate input/output? 6. Why do game programs often send their sound output directly to the sound card’s hardware ports? 7. Challenge: Is it likely that the BIOS for a computer running MS-Windows would be different from that used by a computer running Linux? 2.6 Chapter Summary The central processor unit (CPU) is where calculations and logic processing occur. It contains a limited number of storage locations called registers, a high-frequency clock to synchronize its operations, a control unit, and the arithmetic logic unit. The memory storage unit is where instructions and data are held w...
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