November 2013 Archive


MEMORY MANAGEMENT
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MEMORY MANAGEMENT

Main memory (RAM) is an essential resource that must be carefully handled. While the average home computer nowadays has 10,000 times more memory as the IBM 7094, the largest computer in the world in the early 1960s, programs are getting bigger faster than memories. To

A MEMORY ABSTRACTION: ADDRESS SPACES
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A MEMORY ABSTRACTION: ADDRESS SPACES

On the whole, exposing physical memory to processes has many major drawbacks. First, if user programs can address every byte of memory, they can easily trash the operating system, intentionally or by accident, bringing the system to a grinding halt (unless there is

Swapping
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Swapping

If the physical memory of the computer is large enough to hold all the processes, the schemes explained so far will more or less do. But in practice, the total amount of RAM required by all the processes is often much more than can fit in memory. On a typical Windows or Linux

Managing Free Memory
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Managing Free Memory

When memory is allocated dynamically, the operating system must manage it. Generally, there are two methods to keep track of memory usage: bitmaps and free lists. In this section and the next one we will study these two methods.

VIRTUAL MEMORY
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VIRTUAL MEMORY

As base and limit registers can be used to create the abstraction of address spaces, there is another problem that has to be solved: managing bloatware. While memory sizes are increasing rapidly, software sizes are increasing much faster. In the 1980s, many universities

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