Data that are processed in a computer system include numeric, character, pointer and logical data. Character data, in particular, are data that are represented with the aid of coded character sets (CCSs). This is the focus of this monograph. Although, there have been a sizeable number of published works on such present-day CCSs as ASCII, EBCDIC and Unicode, only few literature materials provide a unified discourse on CCSs as data representation standards. This has been the trend since the publication of C.E. Mackenzie's classic book, 'Coded Character Sets, History and Development' (The Systems Programming Series; Addison-Wesley Publishing Company, 1980). This monograph thus provides a present-day treatise on CCSs via a non-trivial mathematical analysis of the sets. The monograph is suitable for use as a good reference manual for an undergraduate or beginning graduate course on aspects of discrete structures dealing with CCS, and for a course on character data representation. Apart from computer scientists and computer engineers, the monograph is useful to mathematicians who are interested in practical applications of set theory and group presentation theory in computer science.