The term alphanumeric character includes (at least) the letters of a given alphabet , for example English , as well as the ten digits from 0 to 9. In a broader sense, certain special characters (e.g. punctuation marks : period, comma ...; Letters with diacritics , brackets, etc. are included in the alphanumeric characters. The term is mainly used in telecommunications and computer technology.
The adjective alphanumeric is often used with reference to a code or character set , or to describe the properties and possibilities of an input or output device . It is used, for example, to fill in fields in forms . Which exact characters are allowed or supported alphanumeric characters and which are not can be defined differently depending on the location. For example, some systems allow uppercase and lowercase letters, others only uppercase letters, some for example allow German umlauts and the ß, others not.
To store alphanumeric data are often strings ( strings ) are used.