Fictional currency

A fictional currency is some form of system of money defined, depicted, or alluded to, in works of fiction, such as novels, films or video games. The names of units of such currency are sometimes based on extant or historic currencies (e.g. "Altairian dollars" or "Earth yen") while other names, such as "Kalganids" in Asimov's Foundation series, may be wholly invented. A particularly common type, especially in science fiction, is electronically managed "credits". In some works of fiction, exchange media other than money are used. These are not currency as such, but rather nonstandard media of exchange used to avoid the difficulties of ensuring "double coincidence of wants" in a barter system.