Iostream
The most frequently used read/write stream is iostream. We'll look at the implementation shortly.
The stream classes std::istream and std::ostream are often used for the reading and writing of data. Use of std::istream classes requires the <istream> header; use of std::ostream classes requires the <ostream> header. You can have both with the header <iostream>. std::istream is a typedef for the class basic_istream and the character type char, std::ostream for the class basic_ostream respectively:
typedef basic_istream<char> istream;typedef basic_ostream<char> ostream;
C++ has four predefined stream objects for ...