C++ Streams

C++ Streams

• The stream can represent file, console, block of memory or hardware device. The iostream library provides the common set of functions for handling these stream.

Fig. 6.2.1 Stream

• The general representation is ‒

Fig. 6.2.2 Basic level of stream class

•  The stream class hierarchy is divided into three areas:

1. A buffer system given by basic_streambuf class. This class supports the basic low level input output operations. For advanced I/O programming the basic_streambuf class is used directly.

2. The specification system implemented by basic_ios class. This is high level I/O to class that provides formatting, error checking. basic_ios is used as a base for several derived classes, classes, including basic_istream, basic_ostream and basic_iostream. These classes are used to create streams capable of input, output and input/output, respectively.

3. A translation system implemented by certain classes like istream, ostream, iostream. This system converts the objects to a sequence of characters.

• The classes like basic_streambuf or basic_ios are known as template classes. From these template classes the 8‒bit character based classes are derived ‒

Template class   :    8‒bit character class

basic_streambuf :    streambuf

basic_ios : ios

basic_istream : istream

basic_ostream : ostream

basic iostream : iostream

basic_fstream : fstream

basic_ifstream : ifstream

basic_ofstream : ofstream

• This can be presented by following Fig. 6.2.3 of class hierarchy.

Fig. 6.2.3 Stream class hierarchy

Now onwards the character class names will be used because these names are normally used in the program.

Review Questions

1. Explain stream classes for file operations with suitable diagram.

2. List the different stream classes supported in C++.