i am a beginner at C programming and I was trying out a basic function to produce the area of a circle. the radius had to be taken as input from the user. the code is as follows :

#include<stdio.h>
#include<math.h>
float areacircle(float r);
float area;
float r;
int main(){
    
    printf("enter the radius of the circle: ");
    scanf("%f",r);
    areacircle(r);
    return 0;
}


float areacircle(float r){
    area = 3.14*r*r;
    printf("the area of the circle is : %f",area);
}

whenever the user enters any radius, the output is always 0.00. why is this happening ? the output should show the area of the circle according to the radius which has been entered.