FEATURED ESSAYS 1. Parity/Non-parity Check 2. Solving And Checking Equations 3. How A Check Is Processed 4. How To Wash Clothes 5. Address At March On Washington Fo... 6. Online Shopping 7. Valves 8. Getting The Most From Our Educati... 9. The Use Of Credit Cards 10. Plastic Not Paper 11. Rabies 12. Shooting A Rifle 13. The Fbi 14. Problem Solving

Parity/Non-parity Check

Early transmission codes had a serious problem in that a bit could be lost
or gained in transmission because of an electrical or mechanical failure/
If the loss went undetected, the character received on the other end of the
lime was incorrect.

     To Prevent this from happening, a parity check system was developed.
Each character is represented by a byte consisting of a combination of
intelligence bits (seven bits in ASCII and eight bits in EBCDIC) and an
additional bit called a check or parity bit.

     Even parity codes place a check bit with each byte that contains an
uneven number of 1 bits. (Remember that a bit is either 1 or o). Because
the check bit is transmitted only with characters composed of an uneven
number of 1 bits,all characters transmitted will have n even number of 1
bits. The check bit is transmitted to and from the computer along with
character code. If a bit is lost (or added) in transmission, the system
will detect its loss. An uneven number of 1 bits received in a code string
composed of even bits will signal an error.

     Odd Parity codes add a check bit to code combinations that have an
even number of 1 bits. Thus,all characters transmitted have an odd number
of bits. Odd and even parity care similar in nature. They are both designed
to signal an error in the even that data are lost or added.