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Introducing Geographic Information Systems with ArcGIS: A Workbook Approach to Learning GIS, 3rd Edition by Michael D. Kennedy

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Computer Hardware—What a Computer Does

The information in this section is intended to demystify computers for you. As computer power increases—with abilities like speech and facial recognition and championship chess playing—the tendency is to regard a computer as basically incomprehensible. Since the fundamental logical structure behind the operation of a computer is quite simple, I believe such understanding should be part of a student’s knowledge base. It’s not that hard, and you may find it interesting. And the knowledge may help you to figure out why things go wrong sometime when you are using a computer to work on a GIS project.

A refresher: All the operations of a computer are based on the concept that combinations of binary states can represent information. Binary states can be: on or off; A or B; tied or untied; yes or no; exists or does not exist. Customarily, we represent those two states by BInary digiTS (BITS). With these a computer does three things:

  • Strings of 0s and 1s are fed in (input) to the machine and placed electronically into a “store” or “memory.”
  • Bits from the store are manipulated according to a number of exact rules (operations of arithmetic making up a good-sized subset of those rules), and the results of those manipulations are placed back into the store.
  • Strings of 0s and 1s are sent out from the store to output devices.

That’s it! Everything else is simply elaboration on this basic theme.

Why binary states? Because, in the physical world, it is easier ...

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