学习笔记习题3.4：goto 用法

#include<stdio.h>
int main(){
??????? char jx = 0 ;
??????? double number1 = 0.0 ;
??????? double number2 = 0.0 ;

??????? char op = 0 ;
??? loop: printf(" \n Enter the calculation\n");// 定义标识
??????? scanf("? %lf %c %lf",&number1,&op,&number2);
??????? fflush(stdin); //关键点：清除键盘缓存，

??????? switch(op){
??????? case '+' :
??????????????? printf("= %lf \n",number1 + number2);
??????????????? break ;
??????? case '-' :
??????????????? printf("= %lf \n",number1 - number2);
??????????????? break ;
??????? case '*' :
??????????????? printf("= %lf \n",number1 * number2);
??????????????? break ;
??????? case '/':
??????????????? if(number2 == 0){
??????????????????????? printf(" your can't input the zero to /");
??????????????? }else{
??????????????????????? printf("= %lf \n",number1 / number2);
??????????????? }
??????????????? break ;
??????? case '%' :
??????????????????????? if(number2 == 0){
??????????????????????????????? printf(" your can't input the zero to %");
??????????????????????? }else{
??????????????????????????????? printf( " = %ld \n",(long)number1 % (long)number2);
??????????????????????? }
??????????????????????? break;
??????? default :
??????????????? printf(" your have input an error expriese ! ");
??????????????? break ;
??????? }
??????? printf(" 是否进行其它计算 Y/N \?");

??????? scanf("%c",&jx);
??? ??? fflush(stdin); //关键点：清除键盘缓存，
?????
??? ??? if(jx == 'Y' || jx== 'y'){

??????????????? goto loop ; //硬跳转到 loop：语句执行
??????? }else{
??????
??????????????? return 0 ;
??????????????? }

}