Introduction_define

#include <stdio.h>
#define PI 3.1415926
#define MUL(x,y) (x) * (y) // 所有帶入動作最好加括號

int main(){
    int a = PI;
    double b = PI;
    printf("a = %d, b = %lf\n", a, b);
    printf("a * b = %lf", MUL(a,b) );
    return 0;
}