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Unformatted text preview: 1 Computer Logic, Logic Gates, and Building Circuits Matt Huenerfauth CSE 100 Lab Session 1 September 2003 U. of Pennsylvania Image: Intel Museum 2 Logic and Computers The technology inside of computers (and in fact all logical ideas) is based on several simple logic operations: AND OR NOT These logical operations are related to real world equivalents 3 What does AND mean? When we say AND, formally we mean that something is true only when both parts of it are true. If the stove is on AND waters in the kettle , then we will make steam. If either part isnt there, then the result wont be true. 4 What does AND mean in Logic? AND takes two inputs and produces the value TRUE if both inputs are TRUEs. So, with the inputs: T AND T output is: T T AND F output is: F F AND T output is: F F AND F output is: F (Just like in the real world.) 5 A Truth Table A truth table is a convenient way to write down the definition of a logic operation. Lets use 1s for True and 0s for False Heres the table for AND: input input output 1 1 1 1 1 Output of 1 only when both inputs are 1. 6 Truth Table for OR and NOT OR NOT input input output input output 1 1 1 1 1 1 1 1 1 We only need one of the inputs to be true, but if both are true, thats ok, too. This just gives the opposite. 7 A Logic Gate A logic gate is a small computer circuit that simulates one of the logic operators weve seen. There are one or two wires that go into the gate that represent the input. There is one output wire that represents the result of the logic operation. When the power is on, that means True. 8 Logic Gates When drawing diagrams of logic circuits, we use some traditional shapes for each one....
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