How to write a C Program to find the Diameter, Circumference, and Area Of a Circle using Functions with examples? The mathematical formulas behind these calculations are:
- Diameter of a Circle = 2r = 2 * radius
- Circumference of a Circle = 2πr = 2 * π * radius
- Area of a circle is: A = πr² = π * radius * radius
C Program to find Diameter, Circumference, and Area Of a Circle
This program allows the user to enter the radius of a circle. Using that radius value, this C program will find the Diameter, Circumference, and Area Of a Circle
TIP: Please refer Program to Calculate Area article to understand the various Programming ways to calculate the same.
#include<stdio.h> #define PI 3.14 int main() { float radius, area, circumference, diameter; printf("\n Please Enter the radius of a circle : "); scanf("%f",&radius); diameter = 2 * radius; circumference = 2 * PI * radius; area = PI * radius * radius; printf("\n Diameter Of a Circle = %.2f\n", diameter); printf("\n Circumference Of a Circle = %.2f\n", circumference); printf("\n Area Of a Circle = %.2f\n", area); return 0; }

C Program to find Diameter, Circumference, and Area Of a Circle using Functions
In this program, we are using Functions that find the Diameter, Circumference, and Area Of a Circle. Remember, you have to include math.h library to use M_PI. Otherwise, manually define the PI value as we did in the first example.
#include<stdio.h> #include<math.h> double find_Diameter(double radius); double find_Circumference(double radius); double find_Area(double radius); int main() { float radius, area, circumference, diameter; printf("\n Please Enter the radius of a circle : "); scanf("%f",&radius); diameter = find_Diameter(radius); circumference = find_Circumference(radius); area = find_Area(radius); printf("\n Diameter Of a Circle = %.2f\n", diameter); printf(" Circumference Of a Circle = %.2f\n", circumference); printf(" Area Of a Circle = %.2f\n", area); return 0; } double find_Diameter(double radius) { return 2 * radius; } double find_Circumference(double radius) { return 2* M_PI * radius; } double find_Area(double radius) { return M_PI * radius * radius; }
From the above code snippet, you can see we created three functions.
- double find_Diameter(double radius) function to calculate the Diameter of a circle.
- double find_Circumference(double radius) function to calculate the Circumference of a circle.
- And double find_Area(double radius) function to find the Area of a circle.
- Next, we called those functions in the main() program to calculate those values.
When the compiler reaches the above-specified functions in the main() program, the compiler will immediately jump to their respective function definitions.
Please Enter the radius of a circle : 10
Diameter Of a Circle = 20.00
Circumference Of a Circle = 62.83
Area Of a Circle = 314.16
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