#includ<stdio.h>
struct stud{
    int xuehao;
    char name[10];
    float shuxue,yuwen,c;
}    abc;
main()
{   int i,n;
    float j;
    printf("shururenshu:");
    scanf("%d",&n);
    for(i=1;i<=n;i++)
    {
        printf("shuru:%d.xuehao\txingming\n",i);
        scanf("%d",&abc.xuehao);
        scanf("%s",&abc.name);
        printf("shuxue\tyingyu\tc\t\n");
        scanf("%f%f%f\n",&abc.shuxue,&abc.yuwen,&abc.c);

        printf("%d.xuehao:%d",i,abc.xuehao);
        printf("\nxingming:%s",abc.name);j=ave(abc);
        printf("\nave=%f\n",j);
    }
    getch();
}
int  ave(struct stud fa)
{   return  fa.shuxue/3+fa.yuwen/3+fa.c/3;
}

scanf("%d",&abc.xuehao);
fflush(stdin);
scanf("%s",&abc.name);

还是不行。。这是结果。。。

float  ave(struct stud fa)    //应该是float而不是int
 {   return  fa.shuxue/3+fa.yuwen/3+fa.c/3;

 } 

scanf("%f%f%f\n",&abc.shuxue,&abc.yuwen,&abc.c);这里多了个‘\n’"%f%f%f\n"