c语言入门小问题 继续解答

# include<stdio.h>
double average ( int n)
{int iCounter = 0,iGrade;
  float fAverage =0;
    do
  {
      ++iCounter;
      printf("输入课程成绩:");
      scanf("%d",&iGrade);
      fAverage+=iGrade;   
}while(iCounter<n);
   fAverage/=n;
   return fAverage;
}
float max(float f1,float f2, float f3)
{
    float fMax=f1;
    if(f2>fMax)
    fMax=f2;
    if(f3>fMax)
    fMax=f3;
    return fMax;
}

    float count()
{
    int iGrade,iYes,iNum;
     float fCount;
    do
    {
    ++iNum;
    printf("输入C语言成绩:");
   scanf("%d",&iGrade);
    if(iGrade>=60)
    {++iYes;}
}while(iGrade!=-1);
  fCount=(float)iYes/iNum;
  printf("班级及格率为:%f",fCount);
}
int main()
{
    float fAverage,fAverage1,fAverage2,fAverage3;
    fAverage=average(3);
    printf("平均成绩为:%.2f\n",fAverage);
    printf("输入三个学生的成绩:\n");
    scanf("%f%f%f",&fAverage1,&fAverage2,&fAverage3);
    printf("平均分最高的是:%.2f\n",max(fAverage1,fAverage2,fAverage3));
    count();
    return 0;
}