how can i fix this runtime error for a simple code written in c?

February 10, 2022

My code shows me a wrong output by showing the area to be zero:

#include <stdio.h>
double calc(float rad);
void main(void) {
    float rad;
    printf("Enter the circle radius: \n");
    scanf("%f",&rad);
    printf("You entered: %f\n",rad);
        printf("Area is %d\n",calc(rad));
    if(calc(rad)>1000){
       printf("Area is > 1000"); 
    }
    else{
         printf("Area is < 1000"); 
    }
    
}

double calc(float rad){
   double area=3.14*rad*rad;
   return area;
}

Output:

Enter the circle radius : 20
you entered 20.000000
area is 0
area > 1000

Desired output:

Enter the circle radius : 20
you entered 20.000000
area is 1256.000000
area > 1000

>Solution :

The erroneous output is as a result of using %d instead of %lf for double or %f for float in your printf statement. Turning on compiler warning -Wformat will highlight this during compilation