#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;
}
