供参考:
#include<stdio.h>
int main()
{
int n;
printf("input th score:");
scanf("%d", &n);
if (n > 0 && n < 60) printf("score=%d-->E\n",n);
else if (n >= 60 && n < 70) printf("score=%d-->D\n",n);
else if (n >= 70 && n < 80) printf("score=%d-->C\n",n);
else if (n >= 80 && n < 90) printf("score=%d-->B\n",n);
else if (n >= 90 && n <=100) printf("score=%d-->A\n",n);
else printf("score=%d is error!\n",n);
return 0;
}