C Primer Plus6-8

/*8．对练习 7 进行修改，让它使用一个函数来返回计算值。*/#include<stdio.h>#include<stdlib.h>double cal(float,float);int main() {      float a, b;     printf("Please input two number:");     while(scanf("%f %f", &a, &b))         {             printf("%lf\n",cal(a,b));             printf("Please input two number:");         }     system("pause");     return 0; }double cal(float a, float b) {     return (a - b) / (a * b); }