实验7

11-3

#include<iostream>
#include<fstream>
using namespace std;
int main(){
    ofstream out("file1.txt");     
    out << "已成功写入文件！";
    out.close(); 
    return 0;
}

11-4

#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main() {
    string s;
    ifstream in("file1.txt");
    in>>s;
    cout<<s;
    in.close();
    return 0;
}

11-7

#include<iostream>
using namespace std;
int main(){
    ios_base::fmtflags original_flags=cout.flags();//
    cout<<812<<"|";
    cout.setf(ios_base::left,ios_base::adjustfield);//
    cout.width(10);//
    cout<<813<<815<<"\n";
    cout.unsetf(ios_base::adjustfield);//
    cout.precision(2);
    cout.setf(ios_base::uppercase|ios_base::scientific);//
    cout<<813.0;
    cout.flags(original_flags);//
    return 0;
} 

应用1①

#include<iostream>
#include<fstream>
#include<string>
#include<stdlib.h>
#include<ctime>
#include<windows.h> 
using namespace std;
int main(){
    ifstream in("list.txt");
    if(!in) {
        cout << "fail to open." << endl;
        return 1;
    }
    ofstream out("roll.txt");
    if(!out) {
        cout << "fail to open." << endl;
        return 1;
    }
    string a[83];
    int i;
    for(i=0;i<=82;i++){
        getline(in,a[i]);
    }
    for(i=1;i<=5;i++){
        int j=0;
        Sleep(850);
        srand((unsigned)time(NULL));
        j=rand()%83;
        cout<<a[j]<<endl;
        out<<a[j]<<endl;
    }
    in.close();
    out.close();
}

应用2①

 暂时想不到指定文件名的方法……