Professional C++

Chapter 27. Standard Library Header Files

The interface to the C++ Standard Library consists of 51 header files, 18 of which present the C standard library. It's often difficult to remember which header files you need to include in your program files, so this material provides a brief description of the contents of each header, organized into seven categories:

• The C Standard Library

• Containers

• Algorithms, iterators, and allocators

• Utilities

• Exceptions

• Numerical processing

• I/O Streams

The C Standard Library

The C++ Standard Library includes the entire C Standard Library. The header files are generally the same, except for two points:

• The header names are <cname> instead of <name.h>.

• All the names declared in the header files are in namespace std.

For backward compatibility, you can still include <name.h> if you want. That puts the names into the global namespace instead of into namespace std. We recommend avoiding this feature.

The following table provides a summary of the most useful functionality:

Header File Name	Contents
<cassert>	assert() macro.
<cctype>	Character predicates and manipulation functions, such as isspace() and tolower().
<cerrno>	Defines errno expression.
<cfloat>	C-style defines related to floating-point arithmetic, such as FLT_MAX
<ciso646>	In C, the <iso646.h> file defines macros and, or, etc. In C++, those are keywords, so they are not in this header.
<climits>	C-style limit defines, such as INT_MAX.
<clocale>	A few localization macros and functions like LC_ALL and setlocale().
<cmath> ...