Editing C++ Standard Library (section)

==Standard headers==
The following files contain the declarations of the C++ Standard Library.

Legend:<br>
{{color box|#E6E6B7}}: Deprecated<br>
{{color box|#F99}}: Removed

===General===
Components that C++ programs may use for increased features.
{| class="wikitable"
! Name !! Description  
|-
| {{code|<any>}}
|| Added in [[C++17]]. Provides a type-erased class <code>std::any</code>.
|-
| {{code|<atomic>}}
|| Added in [[C++11]]. Provides class template <code>std::atomic</code>, its several template specializations, and more atomic operations.
|-
| {{code|<chrono>}}
|| Provides time elements, such as <code>std::chrono::duration</code>, <code>std::chrono::time_point</code>, and clocks. Since [[C++20]], a hefty amount of temporal features were added: calendars, time zones, more clocks, and string chrono formatting.
|-
| {{code|<concepts>}}
|| Added in [[C++20]]. Provides fundamental library [[Concepts (C++)|concepts]]. 
|-
| {{code|<expected>}}
|| Added in [[C++23]]. Provides class template <code>std::expected</code>, a [[result type]].
|-
| {{code|<functional>}}
|| Provides several [[function object]]s, designed for use with the standard algorithms.
|-
| {{code|<generator>}}
|| Added in [[C++23]]. Provides a [[Generator (computer programming)|coroutine generator]] that additionally supports nested yield operations on ranges.
|-
| {{code|<memory>}}
|| Provides facilities for [[memory management]] in C++, including the class template <code>std::unique_ptr</code>.
|-
| {{code|<memory_resource>}}
|| Added in [[C++17]]. Provides facilities for creating polymorphic memory allocators whose behaviors can change at runtime.<ref>{{Cite web|last=Filipek|first=Bartlomiej|title=Polymorphic Allocators, std::vector Growth and Hacking|url=https://www.bfilipek.com/2020/06/pmr-hacking.html|access-date=2021-04-30|language=en}}</ref>
|-
| {{code|<optional>}}
|| Added in [[C++17]]. Provides class template <code>std::optional</code>, an [[Option type|optional type]].
|-
| {{code|<scoped_allocator>}}
|| Added in [[C++11]]. Provides <code>std::scoped_allocator_adaptor</code>.
|-
| {{code|<stacktrace>}}
|| Added in [[C++23]]. Provides [[stack trace]] operations.
|-
| {{code|<stdexcept>}}
|| Contains standard exception classes such as <code>std::logic_error</code> and <code>std::runtime_error</code>, both derived from <code>std::exception</code>.
|-
| {{code|<system_error>}}
|| Added in [[C++11]]. Defines <code>std::error_code</code>
|-
| {{code|<tuple>}}
|| Added in [[C++11]] and TR1. Provides a class template <code>std::tuple</code>, a [[tuple]].
|-
| {{code|<type_traits>}}
|| Added in [[C++11]]. Provides metaprogramming facilities working with types.
|-
| {{code|<utility>}}
|| The [[Utility (C++)|utility file]] provides various utilities: class template <code>std::pair</code> (two-member [[tuple]]s), compile-time integer sequences, helpers in constructing vocabulary types, functions such as <code>std::move</code> and <code>std::forward</code>, and many more. The namespace <code>std::rel_ops</code> for automatically generating comparison operators is deprecated in [[C++20]] in favor of new defaulted comparison operators.
|-
| {{code|<variant>}}
|| Added in [[C++17]]. Provides a class template <code>std::variant</code>, a [[Tagged union|tagged union type]].
|}

===Language support===
Components that C++ programs may use for support during development.
{| class="wikitable"
! Name !! Description 
|-
| {{code|<compare>}}
|| Added in [[C++20]]. Provides [[Three-way comparison|three-way comparison operator]] support.
|-
| {{code|<coroutine>}}
|| Added in [[C++20]]. Provides [[coroutine]] support.
|-
| {{code|<debugging>}}
|| Added in [[C++26]]. Provides [[debugging]] support.
|-
| {{code|<exception>}}
|| Provides several types and functions related to [[exception handling]], including <code>std::exception</code>, the base class of all exceptions thrown by the Standard Library.
|-
| {{code|<initializer_list>}}
|| Added in [[C++11]]. Provides initializer list support.
|-
| {{code|<limits>}}
|| Provides the class template <code>std::numeric_limits</code>, used for describing properties of fundamental numeric types.
|-
| {{code|<new>}}
|| Provides operators <code>new</code> and <code>delete</code> and other functions and types composing the fundamentals of C++ [[memory management]].
|-
| {{code|<source_location>}}
|| Added in [[C++20]]. Provides capturing source location information as alternative to predefined macros such as <code>__LINE__</code>.
|-
| {{code|<stdfloat>}}
|| Added in [[C++23]]. Provides conditional support for extended floating-point types.
|-
| {{code|<typeinfo>}}
|| Provides facilities for working with C++ [[run-time type information]].
|-
| {{code|<version>}}
|| Added in [[C++20]]. Provides information about the implementation of the C++ standard library.<ref>{{Cite web|date=2020-04-01|title=Working Draft, Standard for Programming Language C++|url=http://open-std.org/JTC1/SC22/WG21/docs/papers/2020/n4861.pdf|url-status=live|access-date=2021-04-30|website=open-std.org|publisher=ISO/IEC|page=492|archive-url=https://web.archive.org/web/20200427145844/http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/n4861.pdf |archive-date=27 April 2020 }}</ref>
|}

===Containers===
{{See also|Standard Template Library}}
Components that C++ programs may use for [[Container (abstract data type)|container data structures]].
{| class="wikitable"
! Name !! Description 
|-
| {{code|<array>}}
|| Added in [[C++11]] and [[C++ Technical Report 1|TR1]]. Provides the container class template <code>[[array (C++)|std::array]]</code>, a container for a fixed sized array.
|-
| {{code|<bitset>}}
|| Provides the specialized container class <code>std::bitset</code>, a [[bit array]].
|-
| {{code|<deque>}}
|| Provides the container class template <code>[[deque (C++)|std::deque]]</code>, a [[deque|double-ended queue]].
|-
| {{code|<flat_map>}}
|| Added in [[C++23]]. Provides the container adapter class templates <code>std::flat_map</code> and <code>std::flat_multimap</code>.
|-
| {{code|<flat_set>}}
|| Added in [[C++23]]. Provides the container adapter class templates <code>std::flat_set</code> and <code>std::flat_multiset</code>.
|-
| {{code|<forward_list>}}
|| Added in [[C++11]] and [[C++ Technical Report 1|TR1]]. Provides the container class template <code>[[forward list (C++)|std::forward_list]]</code>, a [[Linked list|singly linked list]].
|-
| {{code|<inplace_vector>}}
|| Added in [[C++26]]. Provides the class <code>std::inplace_vector</code>, analogous to <code>std::vector</code> with a fixed capacity defined at compile time.
|-
| {{code|<map>}}
|| Provides the container class templates <code>[[map (C++)|std::map]]</code> and <code>std::multimap</code>, sorted [[associative array]] and [[Multimap (data structure)|multimap]].
|-
| {{code|<mdspan>}}
|| Added in [[C++23]]. Provides the class template <code>std::mdspan</code>, analogous to <code>std::span</code> but the view is multidimensional.
|-
| {{code|<queue>}}
|| Provides the container adapter class <code>std::queue</code>, a single-ended [[Queue (data structure)|queue]], and <code>std::priority_queue</code>, a [[priority queue]].
|-
| {{code|<set>}}
|| Provides the container class templates <code>[[set (C++)|std::set]]</code> and <code>std::multiset</code>, sorted associative containers or [[Set (computer science)|set]]s.
|-
| {{code|<span>}}
|| Added in [[C++20]]. Provides the class template <code>std::span</code>, a non-owning view that refers to any contiguous range.
|-
| {{code|<stack>}}
|| Provides the container adapter class <code>[[stack (C++)|std::stack]]</code>, a [[Stack (data structure)|stack]].
|-
| {{code|<unordered_map>}}
|| Added in [[C++11]] and [[C++ Technical Report 1|TR1]]. Provides the container class template <code>[[unordered map (C++)|std::unordered_map]]</code> and <code>std::unordered_multimap</code>, [[hash table]]s.
|-
| {{code|<unordered_set>}}
|| Added in [[C++11]] and [[C++ Technical Report 1|TR1]]. Provides the container class template <code>[[unordered set (C++)|std::unordered_set]]</code> and <code>std::unordered_multiset</code>.
|-
| {{code|<vector>}}
|| Provides the container class template <code>[[vector (C++)|std::vector]]</code>, a [[dynamic array]].
|}

===Iterators and ranges===
Components that C++ programs may use to manipulate iterators, ranges, and algorithms over ranges and containers.
{| class="wikitable"
! Name !! Description 
|-
| {{code|<algorithm>}}
|| Provides definitions of many [[algorithm]]s for use with containers and other ranges.
|-
| {{code|<execution>}}
|| Added in [[C++17]]. Provides execution policies for parallelized algorithms.
|-
| {{code|<iterator>}}
|| Provides classes and templates for working with [[iterator]]s.
|-
| {{code|<numeric>}}
|| Generalized numeric algorithms.
|-
| {{code|<ranges>}}
|| Added in [[C++20]]. Provides [[Range (computer programming)|ranges]] facilities and lazily evaluated adapters.
|}

===Localisation===
Components that C++ programs may use for localisation and character encoding manipulation.
{| class="wikitable"
! Name !! Description 
|-
| style="background:#F99" | {{code|<codecvt>}}
| style="background:#F99" | Provides code conversion facets for various character encodings. Deprecated since [[C++17]], removed in [[C++26]].
|-
| {{code|<locale>}}
|| Defines classes and declares functions that encapsulate and manipulate the information peculiar to a [[Locale (computer software)|locale]].
|-
| {{code|<text_encoding>}}
|| Added in [[C++26]]. Provides text encoding identifications.
|}

===Strings===
Components that C++ programs may use for string manipulation.
{| class="wikitable"
! Name !! Description 
|-
| {{code|<charconv>}}
|| Added in [[C++17]]. Provides a locale-independent, non-allocating, and non-throwing string conversion utilities from/to integers and floating point.
|-
| {{code|<format>}}
|| Added in [[C++20]]. Provides a modern way of formatting strings including <code>std::format</code>.
|-
| {{code|<string>}}
|| Provides the C++ standard [[String (C++)|string]] classes and templates.
|-
| {{code|<string_view>}}
|| Added in [[C++17]]. Provides class template <code>std::basic_string_view</code>, an immutable non-owning view to any string.
|-
| {{code|<regex>}}
|| Added in [[C++11]]. Provides utilities for pattern matching strings using [[regular expressions]].
|}

===Streams, files, and input/output===
Components that C++ programs may use for input/output manipulation and file manipulation.
{| class="wikitable"
! Name !! Description 
|-
| {{code|<filesystem>}}
|| Added in [[C++17]]. Provides facilities for [[file system]] operations and their components.
|-
| {{code|<fstream>}}
|| Provides facilities for file-based input and output. See [[fstream]].
|-
| {{code|<iomanip>}}
|| Provides facilities to manipulate output formatting, such as the [[Radix|base]] used when formatting integers and the [[arithmetic precision|precision]] of [[floating-point arithmetic|floating-point]] values.
|-
| {{code|<ios>}}
|| Provides several types and functions basic to the operation of iostreams.
|-
| {{code|<iosfwd>}}
|| Provides [[forward declaration]]s of several I/O-related class templates.
|-
| {{code|<iostream>}}
|| Provides C++ input and output fundamentals. See [[iostream]].
|-
| {{code|<istream>}}
|| Provides <code>std::istream</code> and other supporting classes for input.
|-
| {{code|<ostream>}}
|| Provides <code>std::ostream</code> and other supporting classes for output.
|-
| {{code|<print>}}
|| Added in [[C++23]]. Provides formatted output utilities such as <code>std::print</code> supported for both C and C++ streams.
|-
| {{code|<spanstream>}}
|| Added in [[C++23]]. Provides <code>std::spanstream</code> and other fixed character buffer I/O streams.
|-
| {{code|<sstream>}}
|| Provides <code>std::stringstream</code> and other supporting classes for string manipulation.
|-
| {{code|<streambuf>}}
|| Provides reading and writing functionality to/from certain types of character sequences, such as external files or strings.
|-
| style="background:#F99" | {{code|<strstream>}}
| style="background:#F99" | Provides input/output operations on array-backed streams. Deprecated in [[C++98]], removed in [[C++26]].
|-
| {{code|<syncstream>}}
|| Added in [[C++20]]. Provides <code>std::osyncstream</code> and other supporting classes for synchronized output streams.
|}

===Thread support library===
Components that C++ programs may use for threading and concurrent programming.
{| class="wikitable"
! Name !! Description 
|-
| {{code|<barrier>}}
|| Added in [[C++20]]. Provides <code>std::barrier</code>, a reusable thread barrier.
|-
| {{code|<future>}}
|| Added in [[C++11]]. In 32.9.1-1, this section describes components that a C++ program can use to retrieve in one thread the result (value or exception) from a function that has run in the same thread or another thread.
|-
| {{code|<hazard_pointer>}}
|| Added in [[C++26]]. Provides [[Hazard pointer|<code>std::hazard_pointer</code>]].
|-
| {{code|<latch>}}
|| Added in [[C++20]]. Provides <code>std::latch</code>, a single-use thread barrier.
|-
| {{code|<mutex>}}
|| Added in [[C++11]]. In 32.5-1, this section provides mechanisms for mutual exclusion: mutexes, locks, and call once.
|-
| {{code|<rcu>}}
|| Added in [[C++26]]. Provides [[Read-copy-update|read-copy-update mechanisms]].
|-
| {{code|<shared_mutex>}}
|| Added in [[C++14]]. Provides facility for shared mutual exclusion.
|-
| {{code|<semaphore>}}
|| Added in [[C++20]]. Provides [[Semaphore (programming)|semaphore]] that models non-negative resource count.
|-
| {{code|<stop_token>}}
|| Added in [[C++20]]. In 32.3.1-1, this section describes components that can be used to asynchronously request that an operation stops execution in a timely manner, typically because the result is no longer required. Such a request is called a stop request.
|-
| {{code|<thread>}}
|| Added in [[C++11]]. Provide class and namespace for working with threads.
|}

===Numerics library===
Components that C++ programs may use to perform seminumerical or mathematical operations.
{| class="wikitable"
! Name !! Description 
|-
| {{code|<bit>}}
|| Added in [[C++20]]. Provides bit manipulation facilities.
|-
| {{code|<complex>}}
|| Defines a class template <code>std::complex</code>, and numerous functions for representing and manipulating complex numbers.
|-
| {{code|<linalg>}}
|| Added in [[C++26]]. Provides [[linear algebra]] facilities.
|-
| {{code|<numbers>}}
|| Added in [[C++20]]. Provides mathematical constants defined in namespace <code>std::numbers</code>.
|-
| {{code|<simd>}}
|| Added in [[C++26]]. Provides data-parallel types and operations on these types.
|-
| {{code|<random>}}
|| Added in [[C++11]]. Facility for generating (pseudo-)random numbers and distributions.
|-
| {{code|<ratio>}}
|| Added in [[C++11]]. Provides compile-time rational arithmetic based on class templates.
|-
| {{code|<valarray>}}
|| Defines five class templates (<code>std::valarray</code>, <code>std::slice_array</code>, <code>std::gslice_array</code>, <code>std::mask_array</code>, and <code>std::indirect_array</code>), two classes (<code>std::slice</code> and <code>std::gslice</code>), and a series of related function templates for representing and manipulating arrays of values.
|}

===C standard library===
{{Main article|C standard library}}
Each header from the C Standard Library is included in the C++ Standard Library under a different name, generated by removing the '{{mono|.h}}' file extension, and adding a '{{mono|c}}' at the start; for example, '<code>time.h</code>' becomes '<code>ctime</code>'. The only difference between these headers and the traditional C Standard Library headers is that where possible the functions should be placed into the <code>std::</code> namespace. In ISO C, functions in the standard library are allowed to be implemented by [[C preprocessor|macros]], which is not allowed by ISO C++.

Usage of the C headers with the '{{mono|.h}}' file extension is legal in C++ and used for compatibility.
{| class="wikitable"
! Name !! Description 
|-
| {{code|<cassert>}}
|| Related to <code>[[assert.h|<assert.h>]]</code>. Declares the [[assertion (computing)|assert]] macro, used to assist with detecting logical errors and other types of bugs while [[debugging]] a program.
|-
| style="background:#F99" | {{code|<ccomplex>}}
| style="background:#F99" | Related to <code>[[complex.h|<complex.h>]]</code>. Defines a [[C mathematical functions#complex.h|set of functions]] for manipulating [[complex number]]s. Deprecated in [[C++17]], removed in [[C++20]].
|-
| {{code|<cctype>}}
|| Related to <code>[[ctype.h|<ctype.h>]]</code>. Defines [[C character classification|set of functions]] used to classify characters by their types or to convert between upper and lower case in a way that is independent of the used [[character set]] (typically [[ASCII]] or one of its extensions, although implementations utilizing [[EBCDIC]] are also known).
|-
| {{code|<cerrno>}}
|| Related to <code>[[errno.h|<errno.h>]]</code>. For testing error codes reported by library functions.
|-
| {{code|<cfenv>}}
|| Related to <code>[[errno.h|<errno.h>]]</code>. Defines a [[C mathematical functions#fenv.h|set of functions]] for controlling [[floating-point]] environment.
|-
| {{code|<cfloat>}}
|| Related to <code>[[float.h|<float.h>]]</code>. Defines [[C data types#float.h|macro constants]] specifying the implementation-specific properties of the [[floating-point]] library.
|-
| {{code|<cinttypes>}}
|| Related to <code>[[inttypes.h|<inttypes.h>]]</code>. Defines [[C data types#inttypes.h|exact-width integer types]].
|-
| style="background:#F99" | {{code|<ciso646>}}
| style="background:#F99" | Related to <code>[[iso646.h|<iso646.h>]]</code>. Defines [[C alternative tokens|several macros]] that implement alternative ways to express several standard tokens. For programming in [[ISO 646]] variant character sets. Removed in [[C++20]].
|-
| {{code|<climits>}}
|| Related to <code>[[limits.h|<limits.h>]]</code>. Defines [[C data types#limits.h|macro constants]] specifying the implementation-specific properties of the integer types.
|-
| {{code|<clocale>}}
|| Related to <code><locale.h></code>. Defines [[C localization functions|localization functions]].
|-
| {{code|<cmath>}}
|| Related to <code>[[math.h|<math.h>]]</code>. Defines [[C mathematical functions|common mathematical functions]]. Extends <code><math.h></code>, containing special mathematical functions such as [[Bessel function]]s and the [[Riemann zeta function]].
|-
| {{code|<csetjmp>}}
|| Related to <code>[[setjmp.h|<setjmp.h>]]</code>. Declares the macros <code>setjmp</code> and <code>longjmp</code>, which are used for non-local exits.
|-
| {{code|<csignal>}}
|| Related to <code>[[signal.h|<signal.h>]]</code>. Defines [[C signal handling|signal-handling functions]].
|-
| style="background:#F99" | {{code|<cstdalign>}}
| style="background:#F99" | Related to <code><stdalign.h></code>. For querying and specifying the [[Data structure alignment|alignment]] of objects. Deprecated in [[C++17]], removed in [[C++20]].
|-
| {{code|<cstdarg>}}
|| Related to <code>[[stdarg.h|<stdarg.h>]]</code>. For [[Linearizability|atomic operations]] on data shared between threads.
|-
| style="background:#F99" | {{code|<cstdbool>}}
| style="background:#F99" | Related to <code>[[stdbool.h|<stdbool.h>]]</code>. Defines [[C data types#stdbool.h|a Boolean data type]]. Deprecated in [[C++17]], removed in [[C++20]].
|-
| {{code|<cstddef>}}
|| Related to <code>[[stddef.h|<stddef.h>]]</code>. Defines [[C data types#stddef.h|several useful types and macros]].
|-
| {{code|<cstdint>}}
|| Related to <code>[[stdint.h|<stdint.h>]]</code>. Defines [[C data types#stdint.h|exact-width integer types]].
|-
| {{code|<cstdio>}}
|| Related to <code>[[stdio.h|<stdio.h>]]</code>. Defines [[C file input/output|core input and output functions]].
|-
| {{code|<cstring>}}
|| Related to <code>[[string.h|<string.h>]]</code>. Defines [[C string handling|string-handling functions]].
|-
| style="background:#F99" | {{code|<ctgmath>}}
| style="background:#F99" | Related to <code>[[tgmath.h|<tgmath.h>]]</code>. Defines [[C mathematical functions#tgmath.h|type-generic mathematical functions]]. Deprecated in [[C++17]], removed in [[C++20]].
|-
| {{code|<ctime>}}
|| Related to <code>[[time.h|<time.h>]]</code>. Defines [[C date and time functions|date- and time-handling functions]].
|-
| {{code|<cuchar>}}
|| Related to <code><uchar.h></code>. Types and functions for manipulating [[Unicode]] characters.
|-
| {{code|<cwchar>}}
|| Related to <code>[[wchar.h|<wchar.h>]]</code>. Defines [[C string handling|wide-string-handling functions]].
|-
| {{code|<cwctype>}}
|| Related to <code>[[wctype.h|<wctype.h>]]</code>. Defines [[C character classification|set of functions]] used to classify wide characters by their types or to convert between upper and lower case.
|}

The following headers are special C compatibility headers which do not have a corresponding C++ naming convention, meaning that the C headers ''must'' be used if the header is necessary.
{| class="wikitable"
! Name !! Description 
|-
| {{code|<stdatomic.h>}}
|| Added in [[C++23]]. Related to <code><stdatomic.h></code>. For [[Linearizability|atomic operations]] on data shared between threads. 
|}
The C headers <code><stdnoreturn.h></code> and <code><threads.h></code> do not have C++ equivalents and their C headers are not supported in C++.

C++ does not provide the [[C POSIX library]] as part of any standard, however it is legal to use in a C++ program. If used in C++, the POSIX headers are not prepended with a "{{mono|c}}" at the beginning of the name, and all contain the {{mono|.h}} suffix in the header name. Most headers in the POSIX library typically have a C++ equivalent implementation, such as <code><regex></code> rather than <code><regex.h></code>.