Standard Header Files

Header files of the C++ standard library

algorithm	ios	map	stack
bitset	iosfwd	memory	stdexcept
complex	iostream	new	streambuf
dequeue	istream	numeric	string
exception	iterator	ostream	typeinfo
fstream	limits	queue	utility
functional	list	set	valarray
iomanip	locale	sstream	vector

Note

Some IDE's put the old-fashioned iostream.h and iomanip.h header files at your disposal. Within these header files the identifiers of iostream and iomanip are not contained in the std namespace but are declared globally.

Header files of the C standard library

assert.h	limits.h	stdarg.h	time.h
ctype.h	locale.h	stddef.h	wchar.h
errno.h	math.h	stdio.h	wctype.h
float.h	setjmp.h	stdlib.h
iso646.h	signal.h	string.h

The C++ standard library header files are shown opposite. They are not indicated by the file extension .h and contain all the declarations in their own namespace, std. Namespaces will be introduced in a later chapter. For now, it is sufficient to know that identifiers from other namespaces cannot be referred to directly. If you merely stipulate the directive

Example:

#include <iostream>

the compiler would not be aware of the cin and cout streams. In order to use the identifiers of the std namespace globally, you must add a using directive.

Example:

#include <iostream>
#include <string>
using namespace std;

You can then use cin and cout without any additional syntax. The header file string has also been included. This makes the string class available and allows user-friendly string manipulations in C++. The following pages contain further details on this topic.

Header Files in the C Programming Language

The header files standardized for the C programming language were adopted for the C++ standard and, thus, the complete functionality of the standard C libraries is available to C++ programs.

Example:

#include <math.h>

Mathematical functions are made available by this statement.

The identifiers declared in C header files are globally visible. This can cause name conflicts in large programs. For this reason each C header file, for example name.h, is accompanied in C++ by a second header file, cname, which declares the same identifiers in the std namespace. Including the file math.h is thus equivalent to

Example:

#include <cmath>
using namespace std;

The string.h or cstring files must be included in programs that use standard functions to manipulate C strings. These header files grant access to the functionality of the C string library and are to be distinguished from the string header file that defines the string class.

Each compiler offers additional header files for platform dependent functionalities. These may be graphics libraries or database interfaces.

Standard Header Files | Header files of the C++ standard library