To maintain odd parity,
•The extra parity bit is turned on when the seven-bit ASCII byte has an even number of on-bits. When the ASCII byte has an odd number of on-bits, the parity bit is turned off.
•The receiving device checks for this condition. A parity error occurs when an even number of on-bits is encountered. Some computer systems are designed to maintain even parity, but odd and even parity work in a similar manner.
In a manner of speaking,
•Computers get sick, too. A variety of highly contagious “diseases” can spread from computer to computer, much the way biological viruses do among human beings.
•A computer virus is a program that literally “infects” other programs and data bases upon contact. It can hide duplicates of itself within legitimate programs, such as an operating system or word processing program.
Virus programs
•Are written with malicious intent and are loaded to the computer system of an unsuspecting victim. Viruses have been found at all levels of computing, from micro-computers to super-computers; however, the micro-computer environment is particularly suceptible to virus infiltration because of the lack of system controls exercised by individual users.
