代码未显示错误却不显示运算结果

#include
int main()
{
int a,b,c;
char op;
scanf_s("%d%c%d",&a,&op,&b);
switch(op)
{
case'+':c=a+b;printf("%d%c%d=%d\n",a,op,b,c);break;
case'-':c=a-b;printf("%d%c%d=%d\n",a,op,b,c);break;
case'':c=ab;printf("%d%c%d=%d\n",a,op,b,c);break;
case'/':if(b!=0)
{ c=a/b;printf("%d%c%d=%d\n",a,op,b,c);}
else
printf("除数有零\n");break;
default:printf("表达式有误\n");
}
return 0;
}
怎么显示不了？

scanf_s("%d%c%d",&a,&op,&b);
改为
scanf_s("%d%c%d",&a,&op,1,&b);