Define PI constant with #define - C Preprocessor

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Description

Define PI constant with #define

Demo Code

#include <stdio.h>

#define PI      3.141592654/*from   w w  w .  ja  va  2s  . c o m*/

//calculate the area of a circle.
double area (double r){
    return PI * r * r;
}

//calculate the circumference of a circle.
double circumference (double r){
    return 2.0 * PI * r;
}

//calculate the volume of a circle.
double volume (double r){
    return 4.0 / 3.0 * PI * r * r * r;
}

int main (void){
    double area (double r);

    double circumference (double r);

    double volume (double r);

    printf ("radius = 1: %.4f    %.4f    %.4f\n", area (1.0), circumference (1.0), volume (1.0));

    printf ("radius = 4.98: %.4f    %.4f    %.4f\n", area (4.98), circumference (4.98), volume (4.98));

    return 0;
}

Result


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