实验7

#include<iostream>
using namespace std;
int main() {
    ios_base::fmtflags original_flags = cout.flags();//保存现在的格式化参数设置,以便将来恢复这些设置 
    cout << 812 << ‘|‘;
    cout.setf(ios_base::left, ios_base::adjustfield);//把对齐方式转为左对齐
    cout.width(10);//把输出域的宽度由0改为10
    cout << 813 << 815 << ‘\n‘;
    cout.unsetf(ios_base::adjustfield);//消除对齐方式的设置 
    cout.precision(2);//设置精度2
    cout.setf(ios_base::uppercase | ios_base::scientific);//更改浮点数的显示设置 
    cout << 831.0;
    cout.flags(original_flags);//恢复初始参数
    return 0;
}

#include<fstream>  
#include<iostream>
using namespace std;
int main() {
    ofstream s("d://text.txt");
    s << "已成功写入文件!" << endl;
    s.close();
    return 0;
}

#include <fstream>
#include<iostream>
using namespace std;
int main()
{
    ifstream s("test1.txt");
    char ch;
    while((ch=s.get())!=EOF)
        cout.put(ch);
    s.close();
    return 0;
}

#include<iostream>
#include<cstring>
#include<fstream>
#include<cstdlib>
#include<ctime>
using namespace std;
struct student
{
    string num;
    string id,name,cls;
}stu[100];
int main()
{
    ifstream fin("list.txt");
    ofstream fout("roll.txt");
    if(!fin)
    {
        cout<<"无法打开文件"<<endl;
        return 1; 
    }
    int i=0;
    while(fin>>stu[i].num>>stu[i].id>>stu[i].name>>stu[i].cls)
    {
        i++;
    }
　　 fin.close();
    int line=i;
    int a;
    srand(time(NULL));
    for(int i=0;i<5;i++)
    {
        a=rand()%line+1;
        cout<<stu[a].num<<" "<<stu[a].id<<" "<<stu[a].name<<" "<<stu[a].cls<<endl;
        fout<<stu[a].num<<" "<<stu[a].id<<" "<<stu[a].name<<" "<<stu[a].cls<<endl;
    }
　　 fout.close();
    return 0;
}