#include
int main()
{
    int score;
    scanf("%d,&score");
    printf("your grade:");
    switch(score)
    {
    case(90~100):printf("a\n");break;
    case(80~89):printf("b\n");break;
    case(70~79):printf("c\n");break;
    case(60~69):printf("d\n");break;
    case(<60):printf("e\n");break;
    }
    return 0;
}

#include
int main()
{
    int score;
    scanf("%d,&score");
    printf("your grade:");
    if (90 <= score && score <=100) {
        printf("a\n");
   }
    else if (80 <= score && score <90) {
       printf("b\n");
    }
    else if (70 <= score && score <80) {
       printf("c\n");
    }
    else if (60 <= score && score <70) {
       printf("d\n");
    }
    else if (0 <= score && score <60) {
       printf("f\n");
    }
   else {
       printf("输入有误。\n");
   }
   
    return 0;
}

     楼上正解。楼主还是多看看书吧。你的case 语句……

#include<stdio.h>
int main()
{
    int score;
    scanf("%d",&score);
    printf("your grade:");
    if (90 <= score && score <=100) {
        printf("a\n");
   }
    else if (80 <= score ) {
       printf("b\n");
    }
    else if (70 <= score ) {
       printf("c\n");
    }
    else if (60 <= score ) {
       printf("d\n");
    }
    else if (0<= score ) {
       printf("f\n");
    }
   else {
       printf("输入有误。\n");
   }
   
    return 0;
} 

#include<stdio.h>
 int main()
 {
     int score,a;

     printf("your grade:\n");
     scanf("%d",&score);

     a=score/10;

     switch(a)
     {
     case 10:
     case  9:
         printf("A\n");break;
     case  8:
         printf("B\n");break;
     case  7:
         printf("C\n");break;
     case  6:
         printf("D\n");break;
     case  5:
     case  4:
     case  3:
     case  2:
     case  1:
         printf("E\n");break;
     default:
         printf("error!\n");
     }
     return 0;
 }

真热闹呀，那我也写一个

#include <stdio.h>

int main()
{
    int score;
    scanf( "%d", &score );
    printf( "your grade:%c\n", "eeeeeedcbaa"[score/10] );

    return 0;
}

精彩

强

这个不错
就是输入非 0-100的数字 可能会内存违规哦

【例5.3】
main(){
int a,b,max;
printf("\n inputtwo numbers:  ");
scanf("%d%d",&a,&b);
max=a;
if (max<b)max=b;
printf("max=%d",max);
}

上的第三横中的\n是什么意思？ 要怎用？