Difference between revisions of "CSC103: DT's Notes 1"
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In our present case, the major influence on the way our computers are build is the fact that we are using electricity as the source of power, and that we're using fast moving electrons to represent, or ''code'' information. Electrons are cheap. They are also very fast, moving at approximately 3/4 the speed of light in wires<ref name="speedElectrons">Main, P., "When electrons go with the flow: Remove the obstacles that create electrical resistance, and you get ballistic electrons and a quantum surprise". New Scientist 1887: 30., 1993. </ref>. We know how to generate them cheaply (power source), how to control them easily (with switches), and how to transfer them (over electrical wires). These properties were the reason for the development of the first vacuum tube computer by Atanasoff in 1939<ref name="atanasoff1939">Ralston, Anthony; Meek, Christopher, eds., Encyclopedia of Computer Science (second ed.), pp. 488–489, 1976.</ref>. | In our present case, the major influence on the way our computers are build is the fact that we are using electricity as the source of power, and that we're using fast moving electrons to represent, or ''code'' information. Electrons are cheap. They are also very fast, moving at approximately 3/4 the speed of light in wires<ref name="speedElectrons">Main, P., "When electrons go with the flow: Remove the obstacles that create electrical resistance, and you get ballistic electrons and a quantum surprise". New Scientist 1887: 30., 1993. </ref>. We know how to generate them cheaply (power source), how to control them easily (with switches), and how to transfer them (over electrical wires). These properties were the reason for the development of the first vacuum tube computer by Atanasoff in 1939<ref name="atanasoff1939">Ralston, Anthony; Meek, Christopher, eds., Encyclopedia of Computer Science (second ed.), pp. 488–489, 1976.</ref>. | ||
| − | + | The choice of using electricity has influenced greatly a fundamental way in which modern computers work. They all use the binary system at the lowest level. Because electricity can be turned ON or OFF with a switch, it was only logical that these two states would be used to represent information. ON and OFF. 0 and 1. True and False. But if we can represent two different states, two different levels of information, can we represent other than 0 or 1? Say 257? Can we also organize electrical circuitry that can perform the addition of two numbers? | |
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| + | The answer is provided by two giants of computer science, '''George Boole''', and '''Claude Shannon''' who worked at very different times. Boole, in the 1840s, conceived an algebra, that is a mathematical system that obeyed the laws an algebra typically verifies, but that was based on only two values, two symbols. Boole's interest was ''logic'' and wether we can represent any expression that is only True or False as a combination of simpler assertions, that themselves can be only True or False. He succeeded in showing that this system of his was indeed an algebra, a '''[http://mathworld.wolfram.com/BooleanAlgebra.html boolean algebra]''', in the mathematical sense. Quite a strong statement, and mostly of use for people interested in logic. | ||
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-Binary sytem: whatever we can do in base 10, we can do in base 2. Algebra. + * 0, 1 | -Binary sytem: whatever we can do in base 10, we can do in base 2. Algebra. + * 0, 1 | ||
-George Boole: logic: True, False, boolean algebra. Three operators: AND, OR, and NOT | -George Boole: logic: True, False, boolean algebra. Three operators: AND, OR, and NOT | ||
Revision as of 09:09, 30 January 2012
