Discrete Math question!?

I've got a homework problem that I don't understand at all...can someone help me out?





We say that a Boolean function on two variables is binary. For example, the operator AND represents a binary Boolean function. (All possible binary Boolean functions are listed in the handout given in class.)





We say that a Boolean function on just one variable is unary. For example, the operator NOT represents a unary Boolean function. (All possible unary Boolean functions are listed in the handout given in class.)





We say that a Boolean function on zero variables is nullary.





Item 1 - How many distinct nullary Boolean functions are possible?





Item 2 - Describe each of them. (How are they computed? What are their values?)





My teacher has never mentioned nullary functions and I don't understand the concept, nor how it's possible to even have a nullary function :/|||Contradiction and Tautologies are not functions, they are observations of the results of functions.





For convenience, constants are considered nullary functions (they take zero arguments, they're just there).