The <iostream> library automatically defines a few standard objects:
The <fstream> library allows programmers to do file input and output with the ifstream and ofstream classes. C++ programmers can also do input and output from strings by using the stringstream class.
Some of the behavior of the C++ I/O streams (precision, justification, etc) may be modified by manipulating various I/O stream format flags.
| I/O Constructors | constructors | 
| bad | true if an error occurred | 
| clear | clear and set status flags | 
| close | close a stream | 
| eof | true if at the end-of-file | 
| exceptions | set the stream to throw exceptions on errors | 
| fail | true if an error occurred | 
| fill | manipulate the default fill character | 
| flags | access or manipulate io_stream_format_flags | 
| flush | empty the buffer | 
| gcount | number of characters read during last input | 
| get | read characters | 
| getline | read a line of characters | 
| good | true if no errors have occurred | 
| ignore | read and discard characters | 
| open | open a new stream | 
| peek | check the next input character | 
| precision | manipulate the precision of a stream | 
| put | write characters | 
| putback | return characters to a stream | 
| rdstate | returns the state flags of the stream | 
| read | read data into a buffer | 
| seekg | perform random access on an input stream | 
| seekp | perform random access on output streams | 
| setf | set format flags | 
| sync_with_stdio | synchronize with standard I/O | 
| tellg | read input stream pointers | 
| tellp | read output stream pointers | 
| unsetf | clear io_stream_format_flags | 
| width | access and manipulate the minimum field width | 
| write | write characters |