写入文件时出现c ++怪异字符

Question

When i run this code, and open the .dat file in notepad/wordpad it shows some weird characters

#include<iostream>
#include<fstream>
using namespace std;

class Student
{
    int rollno;
    char name[20];
    char div[20];
public:
    void accept()
    {
        cout<<"enter rollno"<<endl;
        cin>>rollno;
        cout<<"Enter name"<<endl;
        cin>>name;
        cout<<"Enter div"<<endl;
        cin>>div;
    }
    void write_rec()
    {
        ofstream f;
        f.open("Student.dat",ios::binary|ios::app);
        Student s;
        s.accept();
        f.write((char*)&s,sizeof(s));
        f.close();
    }
    void display()
    {
        ifstream f;
        Student s;
        f.open("Student.dat",ios::binary|ios::in);
        while(f.read((char*)&s,sizeof(s)))
            s.show();
        f.close();
    }
    void show()
    {
        cout<<rollno<<endl;
        cout<<name<<endl;
        cout<<div<<endl;
    }
};
int main()
{
    Student s;
    s.write_rec();
    s.display();

}

The code is getting compiled and run perfectly but when i open the "Student.dat" file it shows some weird characters

Answer 1

This line:

    f.write((char*)&s,sizeof(s));

Is writing the raw binary bytes of your Student object into the file. If that's not the behavior you intended, you'll need to do something else, eg translate the member fields of your Student object (in particular the rollno variable, which is an int ) into ASCII text strings and write those strings into the file instead.

Answer 2

on both places when you open file:

    f.open("Student.dat",ios::binary|ios::app);

and:

    f.open("Student.dat",ios::binary|ios::in);

you open as binary. try to remove this option.

as you can see here and here , these are platform specific behaviors.

take a look at this example

EDIT:

and, of course, as Jeremy observed, you have to write meaningful text to your file. on this line:

    f.write((char*)&s,sizeof(s));

you are actually writing each byte (as (char*)) of your object. if you understand what you're doing, and that's what you want to observe, than ok. but maybe you should compare both outputs, from this method and from Jeremy's suggestion.