10.26

switch

switch(整数值)

{ case 整数常数值==:==
       程式片段；
       break;      跳出switch结构
 default==:==       //在所有case都不符合的情况下执行
         程式片段；

}

#include<stdio.h>
int main(void)
{
    int a,b;
    char op;
    float ans;
    scanf("%d%c%d",&a,&op,&b);
    switch (op)
    {
        case '+':
            ans = a + b;
            break;
        caes '-':
            ans = a - b;
            break;
        case '*' :
            ans = a * b;
            break;
        case '/':
            ans = a / b;
            break;
        default:
            printf("输入错误");

    }

    printf("ans=%f\n",ans);
    return 0;
}

while

while(表示式){程式片段}

#include<stdio.h>
int main(void)
{

    int a = 4;
    int b;
    printf("输入一个数字:\n");
    scanf("%d",&b);
    while(a != b){
        if(a > b)
            printf("too small\n");
        else 
            printf("too large\n");
        printf("输入一个数字\n");
            scanf("%d",&b);
    }
    printf("correct\n");
    return 0;
}

#include<stdio.h>
int main(void)
{
  int a,b,count;
  a = 8;
  count = 1;
  printf("输入一个数字\n");
  scanf("%d",&b);
  while(a != b){
    if(a > b)
      printf("too small\n");
    else 
      printf("too large\n");
    printf("请输入一个数\n");
    scanf("%d",&b);
    count = count +1;

  }
  printf("correct  猜了%d次",count);
}

#include<stdio.h>
int main(void)
{
  int a,b,count;
  a = 8;
  count = 0;
  while(count == 0 || a != b){   //这里是==
     printf("输入一个数字\n");
     scanf("%d",&b);
      count = count +1;
     if(a > b)
      printf("too small\n");
    else if(a < b)
      printf("too large\n");
  }
  printf("correct  猜了%d次",count);
}

#include<stdio.h>
int main(void)
{
    int a,sum;
    printf("请输入一个数字\n");
    scanf("%d",&a);
    sum = a;
    while(a !=0){
        printf("请输入一个数字\n");
        scanf("%d",&a) ;
        sum = a+ sum; 
    } 
    printf("sum =%d\n",sum);
    return 0;
}