Example: Circle Measurement in C

C
C++
C#
Java
Python
PHP
// Circle Measurement
#include <stdio.h>
#include <math.h> // Required for M_PI or custom PI definition

#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif

void calculateCircle() {
    float radius, area, circumference;

    printf("\n--- Circle Calculator ---\n");
    printf("Enter the radius of the circle: ");
    scanf("%f", &radius);

    if (radius <= 0) {
        printf("Error: Radius must be a positive value.\n");
        return;
    }

    area = M_PI * radius * radius; // or pow(radius, 2)
    circumference = 2 * M_PI * radius;

    printf("Area of the circle: %.2f\n", area);
    printf("Circumference of the circle: %.2f\n", circumference);
}