The Standard Library

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C++ contains a large standard library which includes all of the standard C library in addition to many additional modules containing C++ specific classes and functions.

Include Directive

To use a module from the standard library, you use the #include compiler directive. Modules from the C library are specified with the letter c preceding their name

(:source lang=cpp:)

#include <cstdio>
#include <cmath>

while C++ specific modules are indicated by name alone

(:source lang=cpp:)

#include <fstream>

The include directive has two forms. The bracket form illustrated above instructs the compiler to search for modules in the system directories only. To include a custom module (or one not located in he system directories), the module name is enclosed within double quotes

(:source lang=cpp:)

#include "mymodule.h"
#include "graphics/window.h"

Modules in C++ consists of two files: a header file and an implementation file. When a module is included within a program, it is the header file (with a .h extension) that is actually included. Thus, all non standard C and C++ library modules will be specified using a .h file extension.

Namespaces

The latest version of the C++ language has defined the use of namespaces which allow for duplication of function and class names within difference namespaces. All of the standard C++ modules use the std namespace. To use a function, variable or class from the standard namespace, you must either preceed the identifier with std

(:source lang=cpp:)

#include <iostream>

int main()
{
  int age;

  std.cout << "How old are you? ";
  std.cin >> age;
}

or explicity tell the compiler you are using the standard namespace with the using clause

(:source lang=cpp:)

#include <iostream>

using namespace std;

int main()
{
  int age;

  cout << "How old are you? ";
  cin >> age;
}

Standard Library Modules

The following is a list of the standard C library modules included in C++

Header File	Description
cctype	character handling functions.
cerrno	error codes reported by some C functions.
cfloat	characteristics of floating-point types.
climits	sizes of integer types.
cmath	C mathematical functions.
csignal	signal handling functions and values.
cstdarg	variable arguments handling.
cstddef	C standard definitions.
cstdio	C standard and file input/output routines.
cstdlib	C standard general utility functions.
cstring	C-style string functions.
ctime	time and date routines.

The following is a list of the standard C++ library modules

Header File	Description
string	C++ string class for creating string objects.
algorithm	special collection of functions used on ranges.
bitset	container for storing bits.
deque	double ended queue.
list	sequence container implemented as a doubly-linked list.
map	map or dictionary type ADT.
multimap	multi-keyed map.
multiset	multi-key set.
priority_queue	priority queue ADT.
queue	the general queue ADT.
set	strucutre used for storing unique elements.
stack	the general stack ADT.
vector	the general vector ADT.

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