<human>:  How do you define a function in the book ‘The Art of Computer Programming Nobile 1’?
<bot>: That’s a good question. You could define a function by giving a list of inputs and outputs. A function with two inputs and one output is called a unary function, a function with three inputs and one output is called a binary function, and a function with four inputs and one output is called a ternary function.