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

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

CodePudding user response：

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

CodePudding user response：

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

This is the correct code. if you want more information :

https://codeforwin.org/2015/05/list-of-all-format-specifiers-in-c-programming.html

https://www.cplusplus.com/reference/cstdio/printf/

https://aticleworld.com/format-specifiers-in-c/ Please go to the last link first.I am sorry for any bad english.