scanf flag problem

[xtjacob]

So lately I've been learning how to program in C, and I've seem to run into a problem. I was trying to write a program to calculate the area of a rectangle, but I keep running into a problem with my scanf flags when I'm compiling. My code looks like this:

#include <stdio.h>

int main() {
float side1;
float side2;
float area;
printf("Please enter the length of side 1.\n");
scanf("%f", side1);
printf("Please enter the length of side 2.\n");
scanf("%f", side2);
area = side1 * side2;
printf("The area is %f.\n", area);
}

Everytime I try to compile it I get this error:

area.c: In function ‘main’:
area.c:8:3: warning: format ‘%f’ expects type ‘float *’, but argument 2 has type ‘double’
area.c:10:3: warning: format ‘%f’ expects type ‘float *’, but argument 2 has type ‘double

I've tried %f, %e and %g and it always fails. I'm compiling it using "gcc area.c -o area". What seems to be the issue? Thanks!

[MadCow108]

you need to give scanf an address to memory location where it can write the result to.

you give it the address of the stack memory of type float side (= 4 bytes of memory whos content will be interpreted as float) with the & operator:

scanf("%f", &side1);

[xtjacob]

Oh, okay. Thanks!