2. TITLES:
• Use of header file fstream.h
• Types of stream objects
• Open() and close() functions
• File mode constants
• Reading and writing characters from to disk
• Reading and writing objects from to disk
3. FILE STREAM:
• A file stream act as an interface between program and the files
• The stream that supplies data to the program is known as input stream
• The stream that receives data from the program is known as output stream
• Input stream
• read data data
I/P
• Output stream
• Write data data
O/P
ProgramDisk file
4. CLASSES FOR FILE STREAM OPERATIONS:
• Io stream file
• F stream file
ios
Stream buf O streamI stream
Io stream
If stream F stream Of stream File buf
F stream base
5. USING F STREAM.H:
• A stream is a sequence of bytes.
• It is general name given to a flow of data.
• Different streams are used to represent different kinds of data flow.
• ifstream class represents input disk files.
• Ofstream class represents output disk files.
• Fstream for both input and output
6. DIFFERENT CLASSES AND ITS FUNCTIONS:
class functions
File buf It sets the file buffers to read and write.
Member function : open(),close()
Fstream base This is the base class for fstream,ifstream
and ofstream classes.
Member function : All input and output
function open(),close()
ifstream It provide input operation for file.
Member function : get(),getline (),read
(),seekg (),tellg ()
ofstream It provide output operation for file
Member function : put (),write (),seekp (),tellp
()
fstream It is an input and output stream.
7. OPENING AND CLOSING FILES:
• Opening of files can be achieved in two ways:
1. using the constructor function of the stream class
syntax : stream stream object (“name of file name”);
2. using the function open()
syntax : stream stream object;
stream object . Open (“name of file name”);
8. TYPES OF FILES:
• Files are two types:
1. ASCII files or text files:
those files created by storing characters.
2.Binary file:
those files created by storing a block of memory.
9. THE CONCEPT OF FILE MODES:
• It describes how a file is to be used
1. To read from it.
2. To write to it.
3. To append it.
4. To read and write and so on..
syntax : stream object . Open (“file name”, file_mode);
10. TYPES OF FILES:
s.no File modes meaning Stream type
1. ios::in It opens file for
reading
Ifstream
2. ios::out It opens file for
writing
ofstream
3. ios::app It causes all output to
that file to be
appended to the end
ofstream
4. ios::ate It seeks to end-of-file
upon opening of the
file
ofstream
5. ios::trunc Delete contents of
the file if it exists
ofstream
6. ios::nocreate It causes the open ()
functions to fail if the
file does not already
exit.it will not create
a new file with that
ofstream
11. READING AND WRITING CHARACTERS FROM TO
DISK:
• The function put () and get () are used for manipulating a file
character by character.
• These function are members of ostream and istream
respectively
put() is used for output to the file.
get() is used for input from file.
12. #include <fstream.h>
Void main()
{
char ch;
ifstream infile (“out.txt”);
while (infile)
{
infile.get (ch);
cout << ch;
}
infile . Close();l
}
#include <fstream.h>
void main()
{
ofstream outfile (“out.txt”);
char str[]=“This is a text file”;
int i=0;
while (str[i])
outfile.put (str [i++]);
outfile.close ();
}
EXAMPLE PROGRAMS:
To create a file using put() To read a file using get()
13. READING AND WRITING CLASS OBJECTS FROM
TO DISK:
• The functions write() and read() are usually used to transfer a
block of data from and to the file.
• Write () is used for output to the file.
• Read () is used for input from file.
14. • To get the contents from the file
• It takes two arguments
i.e., a pointer to the block and
the size of the block
Eg : std file. Read
((char*&s,sizeof(student));
• It takes two arguments.
i.e., a pointer to the block and
the size of the block.
Eg : std file.write
((char*)&s,sizeof(student));
.
To write to the file To read the file
15. PROGRAM TO CREATE A STUDENT FILE:
#include<fstream.h>
Class student
{
private :
int regno,mark;
char name [20];
public :
void getdata ();
};
void student :: getdata ()
{
cout <<“n enter reg.number :”;
cin >> reg no;
cout <<“n enter name of students”;
gets (name);
cout <<“nenter marks:”;
cin >> marksw;
}
