Extended ASCII (American Standard Code for Information Interchange) is an extension of the standard ASCII character set, which includes additional characters beyond the basic 128 characters defined in the standard ASCII set. Extended ASCII uses 8-bits (or 1 byte) instead of 7-bits to represent each character, which allows for up to 256 possible characters. This means that extended ASCII can represent additional characters beyond the standard ASCII set, such as accented letters, currency symbols, and additional graphical characters. It is important to note that Extended ASCII is not standardized and it's not compatible across all platforms, it is not recommended to use it in modern applications and systems, Unicode is the recommended character encoding standard.