File in C++ is used to read write append data. For doing it we use the classes meant for File handling.

Opening a File:

Opening a file means that a file first needs to opened before performing any manipulation. To open a file for writing either ofstream or fstream object has to be used to open a file  and to open a file for only for reading ifstream object is used.

Here is the example for ofstream

ofstream outfile;
outfile.open("file.dat", ios::out | ios::trunc );

Here is the example for fstream

fstream  afile;
afile.open("file.dat", ios::out | ios::in );

Closing a File

When a C++  program is terminated it deallocate all the memory and close all the opened files.

We use predefined function for it.

void close();

Writing to a File:

ofstream or fstream are the classes that will be used for writing a file.

Reading to a File:

ifstream or fstream are the classes that will be used for reading a file.

#include <fstream>
#include <iostream>
using namespace std;
 
int main ()
{
    
   char data[100];

   // open a file in write mode.
   ofstream outfile;
   outfile.open("afile.dat");

   cout << "Writing to the file" << endl;
   cout << "Enter your name: "; 
   cin.getline(data, 100);

   // write inputted data into the file.
   outfile << data << endl;

   cout << "Enter your age: "; 
   cin >> data;
   cin.ignore();
   
   // again write inputted data into the file.
   outfile << data << endl;

   // close the opened file.
   outfile.close();

   // open a file in read mode.
   ifstream infile; 
   infile.open("afile.dat"); 
 
   cout << "Reading from the file" << endl; 
   infile >> data; 

   // write the data at the screen.
   cout << data << endl;
   
   // again read the data from the file and display it.
   infile >> data; 
   cout << data << endl; 

   // close the opened file.
   infile.close();

   return 0;
}