This chapter is a reference for the entire runtime library. As you can see, it is a big one. To help you find what you need, each header in this chapter is organized in alphabetical order. If you are not sure which header declares a particular type, macro, or other identifier, check the index. Once you find the right page, you can quickly see which header you must #include to define the identifier you need.
The subsections in each header's section describe the functions, macros, classes, and other entities declared and defined in the header. The name of the subsection tells you what kind of entity is described in the subsectione.g., "terminate function," "basic_string class template," and so on. Cross references in each "See Also" heading list intrasection references first, followed by references to other headers (in this chapter) and references to keywords (in Chapter 12).
The subsection for each class or class template contains descriptions of all important members. A few obvious or do-nothing members are omitted (such as most destructors) for the sake of brevity.
The entire standard library resides in the std namespace, except that macros reside outside any namespace. Be sure to check the subsection name closely so you know whether an identifier is a macro or something else. To avoid cluttering the reference material, the std:: prefix is omitted from the descriptions. Examples, however, are complete and show how each namespace prefix is properly used.
Some C++ headers are taken from the C standard. For example, the C standard <stdio.h> has its C++ equivalent in <cstdio>. The C++ version declares all the C names (other than macros) in the std:: namespace but reserves the same names in the global namespace, so you must not declare your own names that conflict with those of the C headers.
Each C header can be used with its C name, in which case the declarations in the header are explicitly introduced into the global namespace. For example, <cstdio> declares std::printf (and many other names), and <stdio.h> does the same, but adds "using std::printf" to bring the name printf into the global namespace. This use of the C headers is deprecated.
The syntax description for most macros shows the macro name as an object or function declaration. These descriptions tell you the macro's type or expected arguments. They do not reflect the macro's implementation. For macros that expand to values, read the textual description to learn whether the value is a compile-time constant.
For an overview of the standard library, see Chapter 8. Chapter 9 presents the I/O portions of the library, and Chapter 10 discusses containers, iterators, and algorithms.
C++ permits two kinds of library implementations: freestanding and hosted. The traditional desktop computer is a hosted environment. A hosted implementation must implement the entire standard.
A freestanding implementation is free to implement a subset of the standard library. The subset must provide at least the following headers, and can optionally provide more: