In this tutorial, i am going to show you how to find or calculate the diameter, circumference and area of a circle using the formula, function, and math modules in c programs.

## All C Programs and Algorithm to Find the Area of a Circle

- Algorithm To Find Diameter, Circumference, and Area of a Circle
- C Program to Find Diameter, Circumference, and Area of a Circle using Formula
- C Program to Find Diameter, Circumference, and Area of a Circle using Function
- C Program to Find Diameter, Circumference, and Area of a Circle using Math Module

### Algorithm To Find Diameter, Circumference, and Area of a Circle

Follow the below given algorithm to write a program to find diameter, circumference and area of a circle; as follows:

- START PROGRAM.
- TAKE RADIUS AS INPUT FROM USER.
- FIND AREA OF DIAMETER, CIRCUMFERENCE, CIRLCE USING THE FOLLOWING FORMULAS:
- diameter = 2 * radius;
- circumference = 2 * PI * radius;
- area = PI * radius * radius;

- PRINT “AREA OF CIRCLE, DIAMETER, CIRCUMFERENCE “
- END PROGRAM.

### C Program to Find Diameter, Circumference, and Area of a Circle using Formula

/* C Program to find Diameter, Circumference, and Area Of a Circle */ #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; }

The result of the above c program; as follows:

Please Enter the radius of a circle : 5 Diameter Of a Circle = 10.00 Circumference Of a Circle = 31.40 Area Of a Circle = 78.50

### C Program to Find Diameter, Circumference, and Area of a Circle using Function

/* C Program to find Diameter, Circumference, and Area Of a Circle */ #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; }

The result of the above c program; as follows:

Please Enter the radius of a circle : 5 Diameter Of a Circle = 10.00 Circumference Of a Circle = 31.42 Area Of a Circle = 78.54

### C Program to Find Diameter, Circumference, and Area of a Circle using Math Module

/** * C program to calculate diameter, circumference and area of circle */ #include <stdio.h> #include <math.h> // Used for M_PI int main() { float radius, diameter, circumference, area; /* * Input radius of circle from user */ printf("Enter radius of circle: "); scanf("%f", &radius); /* * Calculate diameter, circumference and area of circle */ diameter = 2 * radius; circumference = 2 * M_PI * radius; area = M_PI * (radius * radius); /* * Print all results */ printf("Diameter of circle = %.2f units \n", diameter); printf("Circumference of circle = %.2f units \n", circumference); printf("Area of circle = %.2f sq. units ", area); return 0; }

The result of the above c program; as follows:

Enter radius of circle: 10 Diameter of circle = 20.00 units Circumference of circle = 62.83 units Area of circle = 314.16 sq. units

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