C Program to find circumference, diameter and area of a circle

Calculating the circumference, diameter, and area of a circle is a common problem in geometry and mathematics. These calculations are fundamental for various applications, from simple geometry problems to complex engineering designs. In this article, we will write a C program that calculates these three properties of a circle using separate functions for each calculation. This approach will help us understand the modularity and reusability of functions in C programming.

Understanding the Properties of a Circle

To compute the circumference, diameter, and area of a circle, we need to understand the following formulas:

1. Diameter (D): The diameter of a circle is twice the radius.

   D = 2 x r

2. Circumference (C): The circumference is the distance around the circle and is calculated using the formula:

   C = 2 x pi x r

3. Area (A): The area is the space enclosed by the circle and is given by:

   A = pi x r^2

Where r is the radius of the circle and Π (Pi) is approximately 3.14159.

Write a C Program to find circumference, diameter and area of a circle

We will implement a C program that defines three functions: calculateDiameter, calculateCircumference, and calculateArea. Each function will perform one of the calculations based on the radius provided by the user.

#include <stdio.h>
#define PI 3.14159

// Function to calculate the diameter of a circle
double calculateDiameter(double radius) {
    return 2 * radius;
}

// Function to calculate the circumference of a circle
double calculateCircumference(double radius) {
    return 2 * PI * radius;
}

// Function to calculate the area of a circle
double calculateArea(double radius) {
    return PI * radius * radius;
}

int main() {
    double radius, diameter, circumference, area;

    // Input the radius from the user
    printf("Enter the radius of the circle: ");
    scanf("%lf", &radius);

    // Call the functions to calculate diameter, circumference, and area
    diameter = calculateDiameter(radius);
    circumference = calculateCircumference(radius);
    area = calculateArea(radius);

    // Output the results
    printf("Diameter of the circle: %.2lf\n", diameter);
    printf("Circumference of the circle: %.2lf\n", circumference);
    printf("Area of the circle: %.2lf\n", area);

    return 0;
}

Output

Enter the radius of the circle: 5
Diameter of the circle: 10.00
Circumference of the circle: 31.42
Area of the circle: 78.54

Explanation of the Code

1. Constants and Libraries:
   • We define PI as 3.14159, which is used in the formulas for circumference and area.
2. Function calculateDiameter:
   • Takes the radius as input and returns the diameter, calculated as 2 * radius.
3. Function calculateCircumference:
   • Takes the radius as input and returns the circumference, calculated as 2 * PI * radius.
4. Function calculateArea:
   • Takes the radius as input and returns the area, calculated as PI * radius * radius.
5. Main Function main:
   • The user is prompted to enter the radius of the circle.
   • The functions are called to compute the diameter, circumference, and area, and their results are stored in respective variables.
   • The results are then printed to the console.