What is a function? How to declare a function and what is function definition ?

Function

A Function is a set of instructions which is used to perform a specific task. Every C++ program has at least one function which is main(). You can divide your program info different function depending on you.

            Syntax:

                        Return_type function_name(Parameters)

{

                        Statements of the function;

}

Example:

A simple example of the function is the “clrscr()” function which is used to clear the output window.

Function Declaration:

Function declaration means how to declare a function. A basic syntax to declare a

function is as follow:

Return_type function_name (data_type parameter1, …data_type parameterN);

You have to mention the return type, the name of the function, parameters if any and put a terminator “ ; ” at the end.

    If there is no parameter then function will:

            Return_type function_name();

            Example:

            int odd (int);

            Function is declared at the start of the main().

            Function declaration tells the compiler about the structure of the function.

            Function Definition:

            The instructions in the body of a function are collectively called as function definition. It              defines that what a function will do?

            A function definition can be written at

·         Before main()

·         After main()