Function may or may not return a value. If a function returns a value, that must be of a valid data type. This can only be one data type that means if a function returns an int data type than it can only return int and not char or float. Return type may be int, float, char or any other valid data type. How can we return some value from a function? The keyword is return which is used to return some value from the function. It does two things, returns some value to the calling program and also exits from the function. It does two things, returns some value to the calling program and also exits from the function. We can only return a value (a variable or an expression which evaluates to some value) from a function. The data type of the returning variable should match return_value_type data type.
There may be some functions which do not return any value. For such functions, the return_value_type is void. ‘void’ is a keyword of ‘C’ language. The default return_value_type is of data type i.e. if we do not mention any return_value_type with a function; it will return an int value.
The same rules of variable naming conventions are applied to functions name. Function name should be self-explanatory like square, squareRoot, circleArea etc.
Argument list contains the information which we pass to the function. Some function does not need any information to perform the task. In this case, the argument list for such functions will be empty. Arguments to a function are of valid data type like int number, double radius etc.
Declarations and Statements:
This is the body of the function. It consists of declarations and statements. The task of the function is performed in the body of the function.
//The function multiplies an integers to itself and returns the result
Int multiply(int my_number)
Int my_result = 0;
my_result = my_number * my_number;
How a program can use a function? It is very simple. The calling program just needs to write the function name and provide its arguments (without data types). It is important to note that while calling a function, we don’t write the return value data type or the data types of arguments.