C++ program to find the area of a circle using user defined function. 

program using a user-defined function findArea(). This function takes radius as its argument and returns the area of circle. 

C++ program:

 Source Code:

// area of circle using function

#include<iostream>

/*  iostream provides basic

input and output services for C++ programs */ 

using namespace std;

float findArea(float);

//user-defined function findArea()

int main()

// Th execution of program start with the main function  

{ 

// Float is the data type

float radius, area;

//Variable Declarations specify the type followed by the name

   cout<<"Enter the Radius of Circle: ";

// cout is used to display the same statement in the output. 

   cin>>radius;

// cin is used to enter the value by the user.   

area = findArea(radius);

cout<<"\nArea of Circle = "<<area;

cout<<endl;

return 0;

}

float findArea(float r)

{

return (3.14*r*r);

}