Page 285 - DCAP404 _Object Oriented Programming

Object-oriented Programming

Notes ofstream myfile(“data1.dat”, ios::ate);
myfile << “Save this text to the file”;
myfile.close();
}
This program will write Save this text to the file at the end of the file data1.dat without removing
the previous content of the file.
A file can also be opened in mixed mode using OR (|) operator to combine the modes. For
example,

ios::ate | ios::binary
opens the file in binary mode for output at the current pointer position without removing the
previous contents of the file. Another example of mixed mode is given below.

fstream myfile(“data.dat”,ios::in | ios::out);
Input file stream (ifstream) allows only reading from the file and output file stream (ofstream)
only for writing into the file. If you wish to open a file both for writing and reading at the same
time you should use file stream (fstream) with specific opening mode as the following program
demonstrates.

#include <fstream.h>
void main()
{
fstream myfile (“data.dat”,ios::in | ios::out);
myfile << “Write this text”; //Writing into the file
static char TextRead[50]; //Create an array to hold what is

read from the file
myfile.seekg(ios::beg); //Get back to the beginning of
the file explained later
myfile >> TextRead;
cout << TeaxtRaed << endl;
myfile.close();
}
In this program the statement fstream myfile (“data.dat”,ios::in | ios::out); creates an object
from class fstream. At the time of execution, the program opens the file data.dat in read/write
mode (ios::in | ios::out) which allows to read from the file, and put data into it, at the same time.
This is done by allowing the program to move the character pointer in the file to a desired
location before reading or writing.
The read and write operation takes place on the current position of the pointer in the file.
Therefore you might need to shift this position to a desired location. The member function
seekg() of the class fstream allows you to do just that as shown below.
myfile.seekg(ios::beg) //Take the pointer to the beginning of the file
myfile.seekg(ios::end) //Take the pointer to the end of the file

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