How to Find Area of a Circle with Diameter in C++ using Functions | Class | Function Overloading | Constructor

How to find area of a circle with diameter in C++ using functions, class, function overloading, and constructor.

In this article, you will learn how to find area of a circle with diameter in C++ using functions, class, function overloading, and constructor.

 

Example

 

You should have knowledge of the following topics in c++ programming to understand this program:

• C++ cin object
• C++ cout object
• C++ Functions
• C++ Oops
• C++ Function overloading

 

Formula

D = 2 * r

C = 2 * PI * r

A = PI * r2

 

Where

 

There are two ways to solve these problems:

• By using the default value of PI = 3.14
• Second, by using the M_PI constant

 

In this article, we solve this problem in six methods:

1. Using the normal calculation
2. Using the functions
3. Using the Class and Object
4. Using the function overloading
5. Using the Inline Function
6. Using the Constructor

1. Using the default value of PI = 3.14

// How to Find Area of a Circle with Diameter in C++
#include <iostream>
using namespace std;

int main() {
    float r, d = 0, c = 0, a = 0;
    // r = radius of the circle
    // d = diameter of the circle
    // c = circumference of the circle
    // a = the area of the circle

    cout << "Enter the radius of the circle::\n";
    cin >> r;

    // It will calculate the diameter, circumference, and area of the circle
    d = 2 * r;
    c = 2 * 3.14 * r;
    a = 3.14 * (r * r);

    // It will produce the final output
    cout << "\n";
    cout << "Diameter      :: = " << d << " units\n";
    cout << "Circumference :: = " << c << " units\n";
    cout << "Area          :: = " << a << " sq. units\n";
    return 0;
}

Run

Output

 

Explanation

In this given program, we have taken the input 7 the radius of the circle from the user and then applied the standard formula to find the Diameter, Circumference, and Area of the circle.

Then it will return the output values of this program as follows:

• Diameter is 14 units
• Circumference is 43.96 units
• Area is 153.86 sq. units

 

2. Using the M_PI constant

 

// How to Find Area of a Circle with Diameter in C++ using the M_PI constant
#include <iostream>
#include <cmath>
using namespace std;

int main() {
    float r, d = 0, c = 0, a = 0;
    // r is the radius of the circle
    // d is the diameter of the circle
    // c is the circumference of the circle
    // a is the area of the circle

    cout << "Enter the radius of the circle::\n";
    cin >> r;

    // It will calculate the diameter, circumference, and area of the circle
    d = 2 * r;
    c = 2 * M_PI * r;
    a = M_PI * (r * r);

    // It will produce the final output
    cout << "\n";
    cout << "Diameter      :: = " << d << " units\n";
    cout << "Circumference :: = " << c << " units\n";
    cout << "Area          :: = " << a << " sq. units\n";
    return 0;
}

Run

 

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How to Find Area of a Circle with Diameter in C++ using Functions

// How to Find Area of a Circle with Diameter in C++ using Functions
#include <iostream>
using namespace std;

// This function will calculate the area of the circle
void CalculateArea(float x) {
    float d = 0, c = 0, a = 0;
    // d is the diameter of the circle
    // c is the circumference of the circle
    // a is the area of the circle

    // It will calculate the diameter, circumference, and area of the circle
    d = (2 * x);
    c = (2 * 3.14 * x);
    a = 3.14 * (x * x);

    // It will produce the final output
    cout << "\n";
    cout << "Diameter      :: = " << d << " units\n";
    cout << "Circumference :: = " << c << " units\n";
    cout << "Area          :: = " << a << " sq. units\n";
}

// It's the driver function
int main() {
    float r;  // radius of the circle

    cout << "Enter the radius of the circle::\n";
    cin >> r;

    CalculateArea(r);
    return 0;
}

Run

 

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How to Find Area of a Circle with Diameter in C++ using Class and Object

// How to Find Area of a Circle with Diameter in C++ using Class and Object
#include <bits/stdc++.h>
using namespace std;

class Calculation {
public:
    // This method will calculate the area of the circle
    void CalculateArea(float x) {
        float d = 0, c = 0, a = 0;
        // d is the diameter of the circle
        // c is the circumference of the circle
        // a is the area of the circle

        // It will calculate the diameter, circumference, and area of the circle
        d = (2 * x);
        c = (2 * 3.14 * x);
        a = 3.14 * (x * x);

        // It will produce the final output
        cout << "\n";
        cout << "Diameter      :: = " << d << " units\n";
        cout << "Circumference :: = " << c << " units\n";
        cout << "Area          :: = " << a << " sq. units\n";
    }
};

// It's the driver function
int main() {
    float r;  // radius of the circle

    cout << "Enter the radius of the circle::\n";
    cin >> r;

    // To make the instances of the `Calculation` class
    Calculation CA;

    CA.CalculateArea(r);
    return 0;
}

Run

Output

 

---

How to Find Area of a Circle with Diameter in C++ using Function Overloading

// How to Find Area of a Circle with Diameter in C++ using Function Overloading
#include <bits/stdc++.h>
using namespace std;

// This function will calculate the area of the circle
// function with int data type parameter
void CalculateArea(int x) {
    float d = 0, c = 0, a = 0;

    // It will calculate the diameter, circumference, and area of the circle
    d = (2 * x);
    c = (2 * 3.14 * x);
    a = 3.14 * (x * x);

    // It will produce the final output
    cout << "\n";
    cout << "Diameter      :: = " << d << " units\n";
    cout << "Circumference :: = " << c << " units\n";
    cout << "Area          :: = " << a << " sq. units\n";
}

// function with float data type parameter
void CalculateArea(float x) {
    float d = 0, c = 0, a = 0;
    // d is the diameter of the circle
    // c is the circumference of the circle
    // a is the area of the circle

    // It will calculate the diameter, circumference, and area of the circle
    d = (2 * x);
    c = (2 * 3.14 * x);
    a = 3.14 * (x * x);

    // It will produce the final output
    cout << "\n";
    cout << "Diameter      :: = " << d << " units\n";
    cout << "Circumference :: = " << c << " units\n";
    cout << "Area          :: = " << a << " sq. units\n";
}

// It's the driver function
int main() {
    int a = 7;
    float b = 10.4;

    // call function with int data type parameter
    CalculateArea(a);

    // call function with float data type parameter
    CalculateArea(b);

    return 0;
}

Run

Output

 

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How to Find Area of a Circle with Diameter in C++ using inline Function

// How to Find Area of a Circle with Diameter in C++ using inline Function
#include <bits/stdc++.h>
using namespace std;

// This function will calculate the area of the circle
inline void CalculateArea(float x) {
    float d = 0, c = 0, a = 0;
    // d is the diameter of the circle
    // c is the circumference of the circle
    // a is the area of the circle

    // It will calculate the diameter, circumference, and area of the circle
    d = (2 * x);
    c = (2 * 3.14 * x);
    a = 3.14 * (x * x);

    // It will produce the final output
    cout << "\n";
    cout << "Diameter      :: = " << d << " units\n";
    cout << "Circumference :: = " << c << " units\n";
    cout << "Area          :: = " << a << " sq. units\n";
}

// It's the driver function
int main() {
    float r;  // radius of the circle

    cout << "Enter the radius of the circle::\n";
    cin >> r;

    CalculateArea(r);
    return 0;
}

Run 

---

How to Find Area of a Circle with Diameter in C++ using Constructor

// How to Find Area of a Circle with Diameter in C++ using Constructor
#include <bits/stdc++.h>
using namespace std;

class Area {
public:
    float d = 0, c = 0, a = 0;
    // d is the diameter of the circle
    // c is the circumference of the circle
    // a is the area of the circle

    // It will calculate the diameter, circumference, and area of the circle
    Area(float x) {
        d = (2 * x);
        c = (2 * 3.14 * x);
        a = 3.14 * (x * x);
    }

    // It will produce the final output
    void Output() {
        cout << "\n";
        cout << "Diameter      :: = " << d << " units\n";
        cout << "Circumference :: = " << c << " units\n";
        cout << "Area          :: = " << a << " sq. units\n";
    }
};

// It's the driver function
int main() {
    float r;  // radius of the circle

    cout << "Enter the radius of the circle::\n";
    cin >> r;

    // It will create the instance of the `Area` class
    Area AR(r);

    AR.Output();
    return 0;
}

Run

Output

 

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