L25 - Binary Checkbits and Postnet Checkdigits You type...

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Binary Checkbits and Postnet Checkdigits You type messages on a computer using the English alphabet or some equivalent (such as Instant Messaging Language which uses “words” like gtg, irl, lol*, or . All of these are “coded” into numbers which the computer stores in binary. Why binary? Because a single memory cell (and there are millions in a modern computer) either has a charge of static electricity or has none. [ lol: laughing out loud. gtg: got to go. irl: in real life.]
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But memory cells aren’t perfect. What if a tiny charge is present in a cell which shouldn’t have a charge. It is possible that the computer will “read” that cell as charged and interpret it as a 1 instead of as a 0. A clever way has been devised to help overcome this problem. The assumption is that these errors occur infrequently so that there are usually no errors, and if an error occurs we expect at most one error.
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The idea is to append an extra bit to a binary number to make the total number of 1’s even. Example: The binary expression 111_2, which represents seven, has an odd number of 1’s. So we add a “parity check bit” to the right end
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This note was uploaded on 10/11/2011 for the course PSYC, PSYC 2076, 2060 taught by Professor Briganti,gustan,perlis,namikas,wheeler during the Spring '10 term at LSU.

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L25 - Binary Checkbits and Postnet Checkdigits You type...

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