A writ of mandamus or simply mandamus, which means "we order" in Latin, is the name of one of the prerogative writs in the common law, and is a court order directing someone, most frequently a government official, to perform a specified act.
Traditionally, the act to be compelled must be one that is "ministerial" rather than "discretionary," which means it must not involve any qualitative judgment to tell whether it has been done (or done right or completely): Signing a document or handing one over to someone is ministerial; providing some service is discretionary, whether it is painting a portrait or removing a gall bladder or cutting hair or typing a letter. (In that sense, "ministerial" has a "binary" meaning—the act is either done or not done).