从文件读取成绩

从文件中读出学生的成绩，输出最高、最低，以及平均成绩

#include <iostream>
#include <fstream>
#include<cstdlib>   //调用exit(1)需要包含cstdlib
using namespace std;

int main()
{
double max=60,min=50,a,s=0.0;
    int n=0;
    ifstream infile("english.dat",ios::in);
    if(!infile)
    {
        cerr<<"open error!"<<endl;
        exit(1);
    }

while(infile>>a)
{
    if(a>max) max=a;
    else if(a<min)  min=a;
    s+=a;
    n++;
}
infile.close();

    cout << "最高分为" <<max<< endl;
    cout << "最低分为" <<min<< endl;
    cout << "平均分为" <<s/n<< endl;
    return 0;
}

统计各分数段的人数（优秀：≥90，良好：≥80，中等：≥70，及格：≥60，不及格：<60），并将统计结果保存到数据文件中

#include <iostream>
#include <fstream>
#include<cstdlib>   //调用exit(1)需要包含cstdlib
using namespace std;

int main()
{
    double max=60,min=50,a,s=0.0;
    int n=0,A=0,B=0,C=0,D=0,E=0;
    ifstream infile("english.dat",ios::in);
    if(!infile)
    {
        cerr<<"open error!"<<endl;
        exit(1);
    }

    while(infile>>a)
    {
        if(a>=90)  A++;
        else if(a>=80) B++;
        else if(a>=70) C++;
        else if(a>=60) D++;
        else E++;
        if(a>max) max=a;
        else if(a<min)  min=a;
        s+=a;
        n++;
    }
    infile.close();

    ofstream outfile("统计结果.txt",ios::out);
    if(!outfile)
    {
        cerr<<"open error!"<<endl;
        exit(1);
    }
    outfile<<"共有学生"<<n<<"人"<<endl<<endl;
    outfile << "最高分:" <<max<< endl<<endl;
    outfile << "最低分:" <<min<< endl<<endl;
    outfile << "平均分:" <<s/n<< endl<<endl;
    outfile << "优秀人数:" <<A<< endl<<endl;
    outfile << "良好人数:" <<B<< endl<<endl;
    outfile << "中等人数:" <<C<< endl<<endl;
    outfile << "及格人数:" <<D<< endl<<endl;
    outfile << "不及格人数:" <<E<< endl<<endl;

    outfile.close();
    return 0;
}