Since in reality all a computer can store are series of zeros and ones, representing common things like text takes a little work. The solution is to view the series of zeros and ones instead as a sequence of bytes, and map each one to a particular letter, number, or symbol. The full mapping is called a character set. The most popular character set is commonly referred to as ASCII. The second most popular character set these days is Unicode (and it will probably eventually surpass ASCII). Other fairly common character sets include EBCDIC and PETSCII. They are generally quite different from one another; programs exist to convert between them on most platforms, though. Usually EBCDIC is only found on really old machines.