-.-

#include

#define PI 3.1415926

int main( void ) {

/* [a] : Print pi with default floating point output */

double r, area;

printf("My First Program : PI = %f \n, PI" );

printf("半徑長度 :\n");

scanf("%d",&r);

area = r * r * PI;

printf("面積 = : %f \n, area");

return 0;

}