Streams

The data flow between the program and the console or files is called streams. There are two types of streams. They are

• input stream
• output stream

The flow of data from input device to program is called input stream. The flow of data from a program to output device is called output streams.

In C++ different streams are used to represent different types of data flow. Every stream is related with a class which contains its own member functions and the type of data flow.

All I/O stream classes are derived from a base class named as ios. This class is available in the header file iostream.h.

Unformatted I/O

1)Input operation:

The input operations are carried out using the following member function.

a)Overload operator >>

This operator is overloaded in the istream class and is used to give input from keyboard to program. General form:

Cin>>var1>>var2>>…..>>varn;

Where,Cin –    object
>> - operator
var1, var2,…….varn –    C++ variables already declared.

b)get( )

This function is used to input a single character to the program.This is a member function of istream class and is accessed with the help of the object cin.There are two types of

get( ) function.They are

get(char)

get(void)

get(char)

This function is used to assign the input character to its argument. General form:

Cin.get(variable_name);

Where variable_name –   character variable name.

Eg:char opt;

cin.get (opt);

get (void)

This function is used to assign the input character to the variable on the left hand side.

Syntax:

Variable_name = cin.get ( )

Eg:Char opt;

Opt = cin.get ()

c.getline( )

This function is used to input a line of text to the program. This is a member function of istream class and is accessed with the help of the object cin.

General form:

Cin.getline(variable_name, size);

Where size – number of character is the text plus one.The last place is used to store \0.

Variable_name -  valid c++ variable to store the data.

Eg:Char name[10];

Cin.getline(name,10);

2) Output operation:

The output operation is carried out using the following member functions.

a)overloaded operator <<

This operator is overloaded in the ostream class and is used to output data from program to VDU. Syntax:

Cout<< output list;

Where cout – object

<<   - operator

outputlist – the list of variables or constants.

Eg:X= 90;

Y= x +10;

Cout<<

Output: value of x and y are 90,100

b)put ( )

This function is used to output a single character from a program to the VDU. This is a member function of ostream class and is accessed with the help of the object cout. Syntax:

Cout.put (variable_name);

Where,

Variable_name – character variable name.

c)write( )

This function is used to output a line of text from program to VDU.This is a member function of ostream class and is accessed with the help of the object cout. General form:

Cout.write(variable_name, size);

Where, Size – number of characters to display.

Variable_name –  valid c++ variable and its represents the name of the string to be displayed.

Eg:Charname[10];

Cout.write(name,10);