In mathematics, a function is a binary relation between two sets that associates every element of the first set to exactly one element of the second set. Typical examples are functions from integers to integers, or from the real numbers to real numbers. Functions are used for Placing or Storing the Code which is to be Repeated Several Times. A function is a relationship which explains that there should be only one output for each input. It is a special kind of relation (a set of ordered pairs) which obeys a rule, i.e. every y-value should be connected to only one y-value.