求解

#include <stdio.h>
int main()
{
    printf("your grade:\n");
    int grade;
    scanf_s("%d", &grade);
    switch (grade / 10)
    {
    case 10:
    case 9: printf("Grade is A\n");  break;
    case 8: printf("Grade is B\n");   break;
    case 7: printf("Grade is C\n");   break;
    case 6: printf("Grade is D\n");   break;
    case 5: printf("Grade is E\n");   break;
    case 4: printf("Grade is F\n");   break;
    case 3: printf("Grade is G\n");   break;
    case 2: printf("Grade is H\n");   break;
    case 1: printf("Grade is I\n");   break;
    case 0: printf("Grade is J\n");   break;
    }
   
    return 0;
    }
   

怎么用while 语句

不懂while是啥意思

#include <stdio.h>
#include <stdlib.h>

int main()
{
      int i = 0;
      int scores[10];
      
      printf("输入成绩:");
      
      while( i < 10 )//这个循环是用来输入的，不用在意while(),do-while(),for()的用法
    {
          scanf("%d", &scores[i]);//输入时用空格隔开
          i++;
    }
/*----------------------------------------*/
    i = 0;
    
    do{
        
        if( scores[i] >= 90 )
        {
            printf("A\n");
        
        }else if( scores[i] >= 80 && scores[i] <= 89 )
        {
            printf("B\n");
        
        }else if( scores[i] >= 70 && scores[i] <= 79 )
        {
            printf("C\n");
        
        }else if( scores[i] >= 60 && scores[i] <= 69 )
        {
            printf("D\n");
        
        }else if( scores[i] < 60)
        {
            printf("E\n");
        }
        i++;
        
    }while( i < 10 );
    
    system("pause");
    return 0;   
}
/*这个是用的do-while()循环*/

#include <stdio.h>
#include <stdlib.h>

int main()
{
      int i = 0;
      int scores[10];
      
      printf("输入成绩:");
      
      while( i < 10 )//这个循环是用来输入的，不用在意while(),do-while(),for()的用法
    {
          scanf("%d", &scores[i]);//输入时用空格隔开
          i++;
    }
/*----------------------------------------*/
    i = 0;
    
    while( i < 10 )
    {
        if( scores[i] >= 90 )
        {
            printf("A\n");
        
        }else if( scores[i] >= 80 && scores[i] <= 89 )
        {
            printf("B\n");
        
        }else if( scores[i] >= 70 && scores[i] <= 79 )
        {
            printf("C\n");
        
        }else if( scores[i] >= 60 && scores[i] <= 69 )
        {
            printf("D\n");
        
        }else if( scores[i] < 60)
        {
            printf("E\n");
        }
        i++;
        
    }
    
    system("pause");
    return 0;   
}
/*这个是用的while()循环*/

#include <stdio.h>
#include <stdlib.h>

int main()
{
      int i;
      int scores[10];
      
      printf("输入成绩:");
      
      while( i < 10 )//这个循环是用来输入的，不用在意while(),do-while(),for()的用法
    {
          scanf("%d", &scores[i]);//输入时用空格隔开
          i++;
    }
/*----------------------------------------*/    
    for( i = 0; i < 10; i++)
    {
        if( scores[i] >= 90 )
        {
            printf("A\n");
        
        }else if( scores[i] >= 80 && scores[i] <= 89 )
        {
            printf("B\n");
        
        }else if( scores[i] >= 70 && scores[i] <= 79 )
        {
            printf("C\n");
        
        }else if( scores[i] >= 60 && scores[i] <= 69 )
        {
            printf("D\n");
        
        }else if( scores[i] < 60)
        {
            printf("E\n");
        }        
    }
    
    system("pause");
    return 0;   
}
/*这个是用的for()循环*/

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