Error in C concerning double, float variable assignment

Question

#include <stdio.h>

int main(void)
{
    double height; //Error happens if I write double height instead of float height! 
    printf("Height(inch): ");
    scanf("%f",&height);
    printf("%f inch = %f cm \n",height,height*2.54);
}

As you can see in the comment, error happens if I write double height instead of float height! What's wrong with my code?

http://stackoverflow.com/questions/4264127/correct-format-specifier-for-double-in-printf Read (at least the last part of) the accepted answer. — Support Ukraine, Jul 20 '16 at 14:27

score 2 · Accepted Answer · answered Jul 20 '16 at 14:43

The %f format specifier for scanf expects a pointer to a float, not a double. This is significant because the two are different sizes. Passing in the address of a double will result in some but not all of the bytes comprising the double to be populated, resulting in undefined behavior.

To read a value into a double, use %lf.

double height;
scanf("%lf",&height);

Error in C concerning double, float variable assignment

1 Answers1