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Unformatted text preview: tion that asks a question about the result of the last instruction and perhaps changes the contents of the program counter. Figure 5.3 summarizes the fetch-execute cycle. Hardware has changed dramatically in the last half-century, yet the von Neumann machine is still the basis of most computers today. As Alan Perlis, a well-known computer scientist, said in 1981, Sometimes I think the only universal in the computing field is the fetch-execute cycle. 2 This statement is still true today, 20 years later. RAM and ROM We said previously that RAM stands for R andom A ccess M emory. RAM is memory in which each cell (usually byte) can be directly accessed. Inherent in the idea of being able to access each location is the ability to change the contents of each location. That is, storing something else into that place can change the bit pattern in each cell....
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This note was uploaded on 01/13/2011 for the course CSE 1550 taught by Professor Marianakant during the Fall '10 term at York University.
- Fall '10