我自己来补充吧:#include<stdio.h>
#include<string.h>
int
   main ()
  {
      int a,b,s;
      char c;
        printf("请输入表达式\n");
        if(scanf("%d%c%d",&a,&c,&b)==3)
        {
                
            if(c=='+') //加法
            {
                s=a+b;
                printf("%d\n",s);
            }
            else if(c=='-')//减法
            {
                s=a-b;
                printf("%d\n",s);
            }
            else if(c== '*')
            {
                s=a*b;
                printf("%d\n",s);
            }
            else if(c=='/')
            {
       s=a/b
                printf("%.2f\n",a/(float)b);
            
            }
            else if(c=='%')
            {
    s=a%b
        
                printf("%d\n",a%b);
            }
            
        }
    
        
    }