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Parity Code - Computers - Nairaland

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Parity Check 2 (2) (3) (4)

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Parity Code by sil(m): 10:04am On Nov 25, 2006
can some body help tell me what is this parity code as a guildline to help my search?
Re: Parity Code by sbucareer(f): 3:27pm On Nov 25, 2006

Parity code is a bit added to transmitted binary signal either byte or word to reveal errors in the transmission. Let take a printer for example, using a parallel port, the printer will perform what we call handshake to agree on the mode of byte transmission with the other device (Pc). It also include the agreement of parity code for transmission.

If the transmitted byte is wrong the printer would automatically know by the used of the agreed parity code.

<-----------1 byte------------------>
-------------------------------------
| 0 | 1 | 0 | 1 | 1 | 0 | 1 | 1 | 1|
-------------------------------------
The red bit is used to calculate the error byte transmitted. New computers uses 8 bytes to form a word.

Reference: foldoc the online computer dictionary

Re: Parity Code by Kashif(m): 1:30pm On Nov 27, 2006
In addition to the first person pasted, parity code is used in parity check. Odd or even parity check could be used. I odd parity, the system (in handshake) makes sure that the number of 1s (mostly) in the byte or word sums up to an odd number. If it is even parity, the number of the signals (1 or 0) being checked must sum up to an even number.

The problem with parity check however is that if a single code is used as parity and the error comes in two same digits types, the system would not be able to detect it!

Example, if 11010011 is being transmitted from point A to B and one odd parity code is being used, point B will receive 11010011. But check out if something happens on the transmission line and 11010011 is mutated to 11111011, the parity check will fail to detect it! Let me help you to guess why,, the byte still contains an odd number of 1s!! If this does not make sense, kindly revert.

Actually, the more the parity codes, the better the error check but in summary, parity checks are not very reliable. smiley

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