程序代码：

int main()
{
    int x;
    scanf("%d",&x);
    
    switch(x){
        case 1:
            x>=90 && x==100;
            printf("A");
            break;
        case 2 :
            x>=80 && x<=89;
            printf("B");
            break;
        case 3:
            x>=70 && x<=79;
            printf("C");
            break;
        case 4:
            x>=60 && x<=69;
            printf("D");
            break;
        default:
            printf("E");
            break;

    }
}