C Program Structure: Circle area and perimeter calculation

Last update on August 01 2025 13:03:24 (UTC/GMT +8 hours)

4. Circle Structure Calculations

Define a structure named Circle to represent a circle with a radius. Write a C program to calculate the area and perimeter of two circles and display the results.

Sample Solution:

C Code:

#include <stdio.h>

// Define the structure "Circle"
struct Circle {
    double radius;
};

// Function to calculate the area of a circle
double calculateArea(struct Circle c) {
    return 3.14159 * c.radius * c.radius; // Manually define the value of pi
}

// Function to calculate the perimeter (circumference) of a circle
double calculatePerimeter(struct Circle c) {
    return 2 * 3.14159 * c.radius; // Manually define the value of pi
}

int main() {
    // Declare variables to store details for two circles
    struct Circle circle1, circle2;

    // Input details for the first circle
    printf("Input details for Circle 1:\n");
    printf("Radius: ");
    scanf("%lf", &circle1.radius);

    // Input details for the second circle
    printf("\nInput details for Circle 2:\n");
    printf("Radius: ");
    scanf("%lf", &circle2.radius);

    // Calculate and display the area and perimeter for Circle 1
    printf("\nCircle 1:\n");
    printf("Area: %.2lf\n", calculateArea(circle1));
    printf("Perimeter: %.2lf\n", calculatePerimeter(circle1));

    // Calculate and display the area and perimeter for Circle 2
    printf("\nCircle 2:\n");
    printf("Area: %.2lf\n", calculateArea(circle2));
    printf("Perimeter: %.2lf\n", calculatePerimeter(circle2));

    return 0;
}

Output:

Input details for Circle 1:
Radius: 5

Input details for Circle 2:
Radius: 6.3

Circle 1:
Area: 78.54
Perimeter: 31.42

Circle 2:
Area: 124.69
Perimeter: 39.58

Explanation:

In the exercise above,

The "Circle" structure is defined with a member 'radius'.
Two variables ('circle1' and 'circle2') are declared to store details for two circles.
Two functions ("calculateArea()" and "calculatePerimeter()") are defined to calculate the area and perimeter (circumference) of a circle, respectively.
The program prompts the user to input the radius for each circle.
It then calculates and displays the area and perimeter for both circles.

Flowchart:

For more Practice: Solve these Related Problems:

Write a C program to input the radii of two circles, compare their areas, and display both the area and perimeter of each circle.
Write a C program to input an array of Circle structures, then sort and display the circles by their perimeters.
Write a C program to input the radii of three circles, compute the circle with the maximum area, and display its details.
Write a C program to input the radii of two circles and display the ratio of their areas along with both perimeters.

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