缓冲流自动把getchar()填充

 #include"stdio.h"
 #include"conio.h"
 #include<stdlib.h>
 int main()
 {
     char ch1, ch2;
     int i;
     printf("请选择相应的操作:\n1:小写转换大写\n2:大写转换小写\n0:输入错误\n");
     scanf_s("%d",&i);
     printf("\n选择菜单i=%d:", i);
     switch (i)
     {
     case :
         printf("请输入小写字母ch1=");
         getchar();//有缓冲流自动把getchar()填充
         ch1 = getchar();
         //getch(ch1);
         printf("请输入小写字母ch2=");
         getchar();
         //scanf_s("%c",ch2);
         ch2 = getchar();
         ch1 = ch1 - ;
         ch2 = ch2 - ;
         printf("ch1=%c\n", ch1);
         printf("ch2=%c\n", ch2);
         system("pause");
         break;
     case :printf("\n请输入大写字母ch1=");
         getchar();
         ch1 = getchar();
         printf("\n请输入大写字母ch2=");
         getchar();
         ch2 = getchar();
         ch1 = ch1 + ;
         ch2 = ch2 + ;
         printf("ch1=%c\n", ch1);
         printf("ch2=%c\n", ch2);
         system("pause");
         break;
     default:printf("0:输入错误\n\n");
     }
 }