C-Program to Calculate Area and Circumference of a Circle

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
void line()
{
int i;
    printf("\n");
for(i=1;i<=35;i++)
    printf("=");
}
void header()
{
printf("\n");
printf(" Built and Designed by Arslan Malik");
printf("\n");
}
int main()
{
line();
header();
line();
int circumference,radius,area,diameter;
float a=3.14159;
printf("\nEnter radius of circle : \n");
scanf("%d",radius);
circumference=2*a*radius;
printf("Circumference of Circle is : %f \n",circumference);
area=2*a*radius*radius;
printf("Area of circle : %f \n",area);
diameter=2*radius;
printf("Diameter of Circle : %f ",diameter);
return 0;
}