Harvard chart method
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Harvard Chart Method of Logical Equation Reduction[1][2] was developed in response to the need to automate the process of logical equation reduction in the early days of computer hardware and switching circuit development. Large scale production of computer circuitry entailed many more variables than could be reasonably handled by hand using Boolean logic. Logical equation reduction was necessary to minimize logic circuits and thereby reduce the number of logic gates which used vacuum tubes as switches due to their relatively high cost and excessive thermal emission. Logical equations with five of more variables can be reduce to minimum form using Boolean logic but as the number of variables grows the number of operations expands exponentially placing practical limits on doing logical equation reduction by hand. The Harvard Chart Method was developed to solve this problem and to automate the process of logical reduction. The method thus represents one of the first instances of computers being used to design the very circuits of which they are made. Application of this method is limited only by the logical speed and size of the computer (or computer network) on which it is run.
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[edit] Logical Equation Reduction, Simplification or Minimization
(note this chart uses upper case to represent the logic state of "TRUE" and lower case to represent the logic state of "FALSE"
Lets simplify the following equation:
f = ABc + ABC + aBC + aBc + AbC
[edit] The Harvard Chart (style 1)
[edit] The Harvard Chart (style 2)
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The Harvard Chart 1 2 3 4 5 6 7 A B C AB AC BC ABC a b c ab ac bc abc Row1 a b C ab aC bC abC Row2 a B c aB ac Bc aBc Row3 a B C aB aC BC aBC Row4 A b c Ab Ac bc Abc Row5 A b C Ab AC bC AbC Row6 A B c AB Ac Bc ABc Row7 A B C AB AC BC ABC Row8
[edit] The Reduction Steps
[edit] See also
- A Method for Simulating the Process of Logical Human Thought
- See w:table of logic symbols for explanations of symbols used in logic.
[edit] Notes and References
- ↑ *Hunter, William L. [10-1975]. Chapter 4, "The Laws of Logic, Boolean Equation Simplification - The Harvard Chart". Digital/Logic electronics Handbook(in English), pp.112-113, Blue Ridge summit, PA 17214: Tab Books / No. 774, 1975. ISBN 0-8306-5774-6, ISBN 0-8306-4774-0
- ↑ Moved from original location in Wikipedia w:Harvard Chart Method of Logical Equation Reduction to Wikibooks by "author request, no substantial contributions by anyone else"
