C++ In a Nutshell

<fstream>

The <fstream> header declares classes and other types for performing I/O with external files. A file in C++ is a sequence of bytes. A narrow (byte) stream or buffer simply reads or writes those bytes. A wide stream or buffer reads multibyte characters and converts them to wide characters (according to the stream’s locale) or converts wide characters to their multibyte equivalents for writing.

See Chapter 9 for a general discussion of I/O and related topics (stream buffers, locales, and facets), Chapter 1 for more information about character sets, and the <iostream> section in this chapter for information about the base-class templates required by the fstream class templates. Refer to Chapter 8 for information about traits in general and to the <string> section in this chapter for detailed information about the char_traits class template. Refer to the <streambuf> section in this chapter for information about the basic_streambuf class template.

To open a file for reading, use ifstream; for writing, use ofstream; for reading and writing, use fstream; for wide character I/O, use wifstream, wofstream, or wfstream.