/* Note:Your choice is C IDE */
#include "stdio.h"
main()
{
char a;
int b;
scanf("%d",&b);
if (b>=90)
a='A';
else if(80<=a<=89) a='B';
else if(70<=a<=79) a='C';
else if(60<=a<=69) a='D';
else if(0<=a<=59) a='E';
switch(a)
{
case'A':printf("A");break;
case'B':printf("B");break;
case'C':printf("C");break;
case'D':printf("D");break;
case'E':printf("E");break;
deafult:;
}
}

本人新手,请各位帮忙看看毛病在哪儿