Character Sets

A character is one single item of text: a letter, a digit, a punctuation mark, a symbol, a space, or a control character that makes a device do something rather than printing a visible symbol. A word such as chat is simply four characters placed side by side.

Computers cannot store letters directly. Their circuits hold only two states, so everything is kept as binary — patterns of 1s and 0s. To store text, each character is given a number and that number is stored in binary.

Every character gets its own code

A character set is a defined list of every character a computer can recognise, and each character is given a binary code that belongs to it alone. Unique matters: if two different characters shared a code, the computer could not tell them apart, so each character in the set must have its own code that no other character uses.

Imagine a tiny made-up set of five characters: a space stored as 000, p as 001, o as 010, ! as 011 and ? as 100. Here 001 always means p and never anything else, so it cannot be confused with o (010) or ! (011). A character set is not a font or a keyboard layout — a font only decides what a letter looks like, while the set decides which code stands for it.

Why the set has to be agreed

Computers constantly swap text: emails, web pages, word-processed files. That only works if the sender and the receiver use the same or compatible character sets. If one machine's set gives a particular code to b but the receiving machine gives that same code to m, a message about a bat could arrive as mat; where several codes differ, letters are swapped throughout the text. Agreed standards such as ASCII and Unicode prevent this by fixing one meaning for each code, so the same code produces the same character on any device.