大一学了三个月真的找不出来错误

Question

#include<stdio.h>
int main()
{
double score ;
int a=score/10;
printf("请输入您的成绩：\n");
scanf("%lf",&score);
if(score<0||score>100)
{
printf("输入数字有误\n");
}
else
switch(a)
{
case 9:
printf("A\n");
break;
case 8:
printf("B\n");
break;
case 7:
printf("C\n");
break;
case 6:
printf("D\n");
break;
default:
printf("E\n");
break;
}
}
printf("%c\n",a);
return 0;
}

Answer 1

double score ;
printf("请输入您的成绩：\n");
scanf("%lf",&score);
int a=score/10;
先输入再计算a的值