#include<stdio.h>
void main()
{
    int score;
    printf("请输入成绩:");
    scanf("%d",&score);
    if(90<=score<=100);
    printf("A!\n");
    else if(89<=score<=80)
        printf("B!\n");
    else if("79<=score<=70")
        print("C!\n");
    else if(69<=score<=60)
        printf("D!\n");
    else
        printf("E!\n");
}

#include<stdio.h>
void main()
{
    int score;
    printf("请输入成绩:");
    scanf("%d",&score);
    if(90<=score<=100);条件判断不能像数学上那样用一串的连等  if（score>=90 && score<=100）；
    printf("A!\n");
    else if(89<=score<=80)
        printf("B!\n");
    else if("79<=score<=70")括号里不要引号
        print("C!\n");
    else if(69<=score<=60)
        printf("D!\n");
    else
        printf("E!\n");
}

同上！

#include<stdio.h>
void main()
{
    int score;
    printf("请输入成绩:");
    scanf("%d",&score);
    if(score>0&&score<=100);
    {
        if(score>=90) 
        printf("A!\n");
        else if(score>=80)
            printf("B!\n");
        else if(score>=70)
            printf("C!\n");
            else if(score>=60)
            printf("D!\n");
        else 
            printf("E!\n");
    }
}

#include<stdio.h>
main()
{
    int score;
    printf("请输入成绩:");
    scanf("%d",&score);
    char s[]={'A','B','C','D','E'};
    int i=score/10;
    i=i<5?5:i>9?9:i;
    if(score>=0&&score<=100)
    printf("%c!\n",s[9-i]);
}

[此贴子已经被作者于2015-10-26 12:36编辑过]