The document discusses file handling in C++ using object oriented programming. It covers key concepts like opening and closing files, reading and writing to files, file pointers, error handling and random access operations. Classes like ifstream, ofstream and fstream are used for input, output and input/output file operations. Functions like open(), close(), get(), put(), read(), write(), seekg(), seekp() etc. are used to perform various file operations.

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By
Nilesh Dalvi
LLeeccttuurreerr,, PPaattkkaarr--VVaarrddee CCoolllleeggee..
http://www.slideshare.net/nileshdalvi01

2. Introduction
• A file is a collection of related data stored on
a particular area on the disk.
• Programs can be designed to perform the
read and write operations on these files.
• Programs can involves either or both
following communication:
1. Data transfer between console unit and
program
2. Data transfer between program and disk file
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

3. Introduction
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

4. Introduction
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

5. Classes for File stream operations
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

6. Classes for File stream operations
• Includes ifsteam, ofstream and fstream.
• These classes are derived from fstreambase
and corrosponding iostream class.
• Are declared in fstream.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

7. Details of file stream classes
Class Contents
filebuf Purpose is to set file buffers to read and write.
Contains close() and open().
fstreambase Provides operations common to the file streams.
Serves as base for ifsteam, ofstream and fstream.
Contains close() and open().
ifstream Provides input operations
Contains open()
Inherits get(), getline(), read(), seekg(), tellg() from istream.
ofstream Provides output operations
Contains close()
Inherits put(), write(), seekp(), tellp() from ostream.
fstream Provides I/O operations
Inherits al functions from istream and ostream from iostream.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

8. Opening and closing a File
• If we want to use a disk file, we need
following things
1. Suitable name for file
2. Data type and structure
3. Purpose
4. Opening method
• A file can be opened in two ways
1. Using constructor
2. Using member function open()
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

9. Opening and closing a File
Opening file using constructor involves 2 steps:
1. Create a file stream object
• ofstream is used for o/p stream
• ifstream is used to create i/p stream
1. Initialize the file object with desired file name.
For example,
ofstream outfile(“results”); // output only
Similarly,
ifstream infile(“data”); // input only
outfile << “Total”;
outfile << sum;
infile >> number;
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

11. Opening and closing a File
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
#include <iostream>
#include <fstream>
using namespace std;
int main ()
{
char name[20];
int age;
ofstream out ("text");
cout << "n Name: ";
cin >> name;
cout << "n Age: ";
cin >> age;
out << name<<"t";
out << age<<"t";
out.close();
ifstream in("text");
in >> name;
in >> age;
cout << "nName t:"<<name<<"n";
cout << "Age t:"<<age;
in.close();
return 0;
}
Output:
Name: ABC
Age: 20
Name :ABC
Age :20

12. Opening and closing a File
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
#include <iostream>
#include <fstream>
using namespace std;
int main ()
{
ofstream fout;
fout.open("out.txt");
char str[300]="Time is a great teacher but
unfortunately it kills all its pupils.";
fout<<str;
fout.close();
return 0;
}

13. Opening and closing a File
#include <iostream>
#include <fstream>
using namespace std;
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
int main ()
{
ifstream fin;
fin.open("out.txt");
char ch;
while(fin)
{
fin.get(ch);
cout<<ch;
}
fin.close();
return 0;
}

14. Checking for errors
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
#include <iostream>
#include <fstream>
using namespace std;
int main ()
{
ifstream fin;
char *f_name = "out1.txt";
fin.open(f_name);
char ch;
if(!fin)
{
cerr << "Error in opening file: "<< f_name << endl;
return 1;
}
while(fin)
{
fin.get(ch);
cout<<ch;
}
fin.close();
return 0;
}

15. Finding end of file
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
#include <iostream>
#include <fstream>
using namespace std;
int main ()
{
ifstream fin;
char *f_name = "afile";
fin.open(f_name);
char ch;
if(!fin)
{
cerr << "Error in opening file: "<< f_name << endl;
return 1;
}
while(fin.eof()==0)
{
fin.get(ch);
cout<<ch;
}
cout << endl;
fin.close();
return 0;
}

16. File opening modes
• Opening file also involves several modes
depending upon operation to be carried out
with the file.
• Syntax of open() function
object.open(“file_name”, mode);
• Here, mode in which file is to be opened.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

17. File opening modes
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
Mode
Parameter
Operation
ios::app Append data at the end of file
ios::ate After opening character pointer goes to
end of file
ios::binary File open in binary mode
ios::in Open file for reading only
ios::out Open file for writing only
ios::nocreate Open unsuccessful if the file does not exist
ios::noreplace Open unsuccessful if the file already exist
ios::trunc Delete the contents of the file if it exist

18. File opening modes
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
#include <iostream>
#include <fstream>
using namespace std;
int main ()
{
char data[100],ch;
ofstream out;
out.open("text",ios::out | ios::binary);
cout << "Enter the text: " << endl;
cin >> data;
out << data;
out.close();
cout << "Content of the file: "<<endl;
ifstream fin;
fin.open("text",ios::in | ios::binary);
fin.get(ch);
while(fin.eof()==0)
{
cout<<ch;
fin.get(ch);
}
cout << endl;
fin.close();
return 0;
}
Output:
Enter the text:
Programming
Content of the file:
Programming

19. File pointers and Manipulators
• All file objects hold two file pointers
associated with the file.
• (input) get pointer helps in reading the file
from given location.
• (output) put pointer helps for writing data
in the file at specified location.
• They are by default set at the beginning of
the file.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

20. File pointers and Manipulators
• To explicitly set stream classes provide following
functions:
• Read mode when file is opened in read mode, get
pointer is set at the beginning of the file.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

21. File pointers and Manipulators
• write mode when file is opened in write mode, put
pointer is set at the beginning of the file.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

22. File pointers and Manipulators
• Append mode this mode allows to add data at the
end of the file.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

23. File pointers handling functions
Function Uses Remark
tellg() gives the current position of the get
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
pointer
Member of ifstream class
seekg() moves get pointer(input) to a specified
location
Member of ifstream class
tellp() gives the current position of the put
pointer
Member of ofstream class
seekp() moves put pointer (output) to a specified
location
Member of ofstream class
• seekg() and tellg() are the member functions of
ifstream.
• seekp() and tellp() are the member functions of
ofstream.

24. File pointers and Manipulators
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
#include <iostream>
#include <fstream>
using namespace std;
int main ()
{
char data[32];
int r;
ofstream out;
out.open("text",ios::out);
cout << "Enter the text: " << endl;
cin.getline(data, 20);
out << data;
out.close();
ifstream fin;
cout << "Content of the file: "<<endl;
fin.open("text",ios::in);
while(fin.eof()==0)
{
fin >> data;
cout << data;
r = fin.tellg();
cout << "("<< r <<")";
}
fin.close();
return 0;
}
Output:
Enter the text:
Programming with C++
Content of the file:
Programming(11)with(16)C+(19)

25. Manipulators with Arguments
• seekp() and seekp() are used with two arguments
seekg(offset, pre_position);
seekp(offset, pre_position);
• offset – number of bytes the file pointer is to be
shifted from the arguments pre_position.
• offset must be positive or negative number.
• pre_position have one of following:
– ios::beg beginning of the file
– ios::cur Current position of the file pointer
– ios::end End of the file.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

26. File pointers and Manipulators
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
#include <fstream>
#include <iostream>
using namespace std;
int main()
{
ofstream out("mydoc.txt",ios::binary);
char text[80],ch;
strcpy(text,"Hi this is a test file!");
out<<text;
out.close();
ifstream in("mydoc.txt",ios::binary);
in.seekg(8);
cout<<endl<<"Starting from position 8 the contents are:"<<endl;
while (!in.eof())
{
in.get(ch);
if (!in.eof())
{
cout<<ch;
}
}
in.close();
return 0;
}
Output:
Starting from position 8 the contents are:
is a test file!

27. File pointers and Manipulators
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
#include <iostream>
#include <fstream>
using namespace std;
int main ()
{
char data[32],ch;
int r;
ofstream out;
out.open("text",ios::out);
cout << "Enter the text: " << endl;
cin.getline(data, 20);
out << data;
out.close();
ifstream in;
cout << "Reverse Contents of the file: "<<endl;
in.open("text",ios::in);
in.seekg(0,ios::end);
int m = in.tellg();
for(int i = 1; i <= m; i++)
{
in.seekg(-i, ios::end);
in >> ch;
cout << ch;
}
in.close();
return 0;
}
Output:
Enter the text:
Happy
Reverse Contents of the file:
yppaH

28. File pointers and Manipulators
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
#include <iostream>
#include <fstream>
using namespace std;
int main ()
{
char data[30],ch;
int r;
ofstream out;
out.open("text",ios::out);
cout << "Enter the text: " << endl;
cin.getline(data, 20);
out << data;
out.seekp(0, ios::beg);
cout << "Enter the text to replace 1st word of 1st text:: "<<endl;
cin.getline(data,20);
out << data;
out.close();
ifstream in;
cout << "Contents of the file: "<<endl;
in.open("text",ios::in);
while(in.eof()==0)
{
in.getline(data,20);
cout << data;
}
in.close();
return 0;
}
Output::
Enter the text:
kk ll mm nn
Enter the text to replace 1st word of 1st text::
oo
Contents of the file:
oo ll mm nn

29. Sequential read and write operations
put() and get() function
• the function put() writes a single character
to the associated stream.
• the function get() reads a single character
form the associated stream.
• Example :
file.get(ch);
file.put(ch);
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

30. Sequential read and write operations
#include <iostream>
#include <fstream>
using namespace std;
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
int main()
{
char c;
ofstream ofs("file.txt");
do
{
c = cin.get();
ofs.put(c);
}while (c != '!');
ofs.close();
return 0;
}

31. Sequential read and write operations
write() and read() function
• write() and read() functions write and read blocks
of binary data.
• Syntax:
file.read((char *)&P, sizeof(P));
file.write((char *)&P, sizeof(P));
• Two parameters, first is address of the variable and
second is size of variable P in bytes.
• Address is converted to char type.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

32. Sequential read and write operations
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
#include <fstream>
#include <iostream>
using namespace std;
int main()
{
int marks[5] = {10, 20, 30, 40, 50};
ofstream ofs("marks.txt");
ofs.write((char *) & marks, sizeof (marks));
ofs.close();
for (int i = 0; i < 5; i++)
{
marks[i] = 0;
}
ifstream ifs("marks.txt");
ifs.read((char *) & marks, sizeof (marks));
ifs.close();
for (int i = 0; i < 5; i++)
{
cout << "marks[" << i << "] = " << marks[i] << endl;
}
return 0;
}
Output::
marks[0] = 10
marks[1] = 20
marks[2] = 30
marks[3] = 40
marks[4] = 50

33. Error Handling Functions
FUNCTION RETURN VALUE AND MEANING
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
eof()
returns true (non zero) if end of file is
encountered while reading; otherwise
return false(zero)
fail()
return true when an input or output
operation has failed
bad()
returns true if an invalid operation is
attempted or any unrecoverable error has
occurred.
good() returns true if no error has occurred.

34. Random Access Operation
• Random-access files enable you to read or
write records in any order.
• Even if you want to perform sequential
reading or writing of the file, you can use
random-access processing and randomly
read or write the file sequentially from the
first record to the last.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

35. Random Access Operation
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).