CMPS340 File Processing Notes on Coding and Data Compression

Coding has to do with representing data or information using a string of symbols over some alphabet.1 Often the term is used in referring to the translation of data represented by a string over one alphabet into a string over a different alphabet. The widely used ASCII (“American Standard Code for Information Interchange”), for example, associates a bit string of length seven to each of the 27 members of what could be called the “ASCII alphabet”, which contains just about every character commonly used in the English language, including the roman letters (both lower and upper case), decimal digits, and common punctuation symbols, as well as some control characters (e.g., line feed, carriage return, backspace).2 Given that the character is a basic form of data and that electronic computers represent data in the form of bit strings, it is only natural that some such coding standard be adopted.