C++ streams

A stream is a logical device that either produces or consumes information. A stream is linked to a physical device by the I/O system.

A stream acts like a source or destination. The source stream that provides data to the program is called the input stream and the destination stream that receive output from the program is called the output stream.

C++ contains cin and cout predefined streams that opens automatically when a program begins its execution.cin represents the input stream connected to the standard input device and cout represents the output stream connected to standard output device.

C++ Stream Classes:

The C++ I/O system contains a hierarchy of classes that are used to define various streams to deal with both the console and disk files. These classes are called stream classes. These classes are declared in the header file iostream. The file should be included in all programs that communicate with the console unit.

As shown in figure ios is the base class for istream(input stream) and ostream(output stream) which are base classes for iostream(input/output stream).

The class ios is declared as the virtual base class so that only one copy of its members are inherited by the iostream.

The class ios provides the basic support for formatted and unformatted input/output operations.The class istream provides the facilities for formatted and unformatted input while the class ostream(through inheritance) provides the facilities for formatted output.

The class iostream provides the facilities for handling both input output streams. Three classes namely istream_withassign, ostream_withassign and iostream_withassign add assignment operators to these classes.