#define in c

// Step 1: Include necessary header files
#include <iostream>

// Step 2: Define a constant using #define
#define PI 3.14159

// Step 3: Main function
int main() {
    // Step 4: Declare variables
    double radius, area;

    // Step 5: Prompt user for input
    std::cout << "Enter the radius of a circle: ";

    // Step 6: Read user input
    std::cin >> radius;

    // Step 7: Calculate area using the defined constant
    area = PI  radius  radius;

    // Step 8: Display the result
    std::cout << "The area of the circle is: " << area << std::endl;

    // Step 9: Return 0 to indicate successful completion
    return 0;
}