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 Each character is represented by a byte consisting ofa combination of intelligence bits (seven bits in ASCII and eightbits in EBCDIC) and an additional bit called a check or paritybit. Even parity codes place a check bit with each byte thatcontains an uneven number of 1 bits. (Remember that a bit iseither 1 or o). Because the check bit is transmitted only withcharacters composed of an uneven number of 1 bits,all characterstransmitted will have n even number of 1 bits. The check bitis transmitted to and from the computer along with charactercode. If a bit is lost (or added) in transmission, the systemwill detect its loss. An uneven number of 1 bits received in acode string composed of even bits will signal an error. Odd Parity codes add a check bit to code combinations thathave an even number of 1 bits. Thus,all characters transmittedhave an odd number of bits. Odd and even parity care similar innature. They are both designed to signal an error in the eventhat data are lost or added....
