The Function prototype serves the following purposes –
1) It tells the return type of the data that the function will return.
2) It tells the number of arguments passed to the function.
3) It tells the data types of each of the passed arguments.
4) Also it tells the order in which the arguments are passed to the function.
Therefore essentially, the function prototype specifies the input/output interlace to the function i.e. what to give to the function and what to expect from the function.
The prototype of a function is also called the signature of the function.
