C++ Standard Library headers

The interface of C++ standard library is defined by the following collection of headers.

Multi-purpose headers
<cstdlib>	General purpose utilities: program control, dynamic memory allocation, random numbers, sort and search
<execution> (C++17)	Predefined execution policies for parallel versions of the algorithmsand execution control components(since C++26)
Language support library
<cfloat>	Limits of floating-point types
<climits>	Limits of integral types
<compare> (C++20)	Three-way comparison operator support
<coroutine> (C++20)	Coroutine support library
<csetjmp>	Macro (and function) that saves (and jumps) to an execution context
<csignal>	Functions and macro constants for signal management
<cstdarg>	Handling of variable length argument lists
<cstddef>	Standard macros and typedefs
<cstdint> (C++11)	Fixed-width integer types and limits of other types
<exception>	Exception handling utilities
<initializer_list> (C++11)	std::initializer_list class template
<limits>	Query properties of arithmetic types
<new>	Low-level memory management utilities
<source_location> (C++20)	Supplies means to obtain source code location
<stdfloat> (C++23)	Fixed-width floating-point types
<typeindex> (C++11)	std::type_index
<typeinfo>	Runtime type information utilities
<version> (C++20)	Supplies macros for verifying implementation status of library
Concepts library
<concepts> (C++20)	Fundamental library concepts
Diagnostics library
<cassert>	Conditionally compiled macro that compares its argument to zero
<cerrno>	Macro containing the last error number
<debugging> (C++26)	Debugging library
<stacktrace> (C++23)	Stacktrace library
<stdexcept>	Standard exception types
<system_error> (C++11)	Defines std::error_code, a platform-dependent error code
Memory management library
<memory>	High-level memory management utilities
<memory_resource> (C++17)	Polymorphic allocators and memory resources
<scoped_allocator> (C++11)	Nested allocator class
Metaprogramming library
<ratio> (C++11)	Compile-time rational arithmetic
<type_traits> (C++11)	Compile-time type information utilities
General utilities library
<any> (C++17)	std::any class
<bit> (C++20)	Bit manipulation functions
<bitset>	std::bitset class template
<expected> (C++23)	std::expected class template
<functional>	Function objects, Function invocations, Bind operations and Reference wrappers
<optional> (C++17)	std::optional class template
<tuple> (C++11)	std::tuple class template
<utility>	Various utility components
<variant> (C++17)	std::variant class template
Containers library
<array> (C++11)	std::array container
<deque>	std::deque container
<flat_map> (C++23)	std::flat_map and std::flat_multimap container adaptors
<flat_set> (C++23)	std::flat_set and std::flat_multiset container adaptors
<forward_list> (C++11)	std::forward_list container
<inplace_vector> (C++26)	std::inplace_vector container
<list>	std::list container
<map>	std::map and std::multimap associative containers
<mdspan> (C++23)	std::mdspan view
<queue>	std::queue and std::priority_queue
<set>	std::set and std::multiset associative containers
<span> (C++20)	std::span view
<stack>	std::stack container adaptor
<unordered_map> (C++11)	std::unordered_map and std::unordered_multimap
<unordered_set> (C++11)	std::unordered_set and std::unordered_multiset
<vector>	std::vector container
Iterators library
<iterator>	Range iterators
Ranges library
<generator> (C++23)	std::generator class template
<ranges> (C++20)	Range access, primitives, requirements, utilities and adaptors
Algorithms library
<algorithm>	Algorithms that operate on ranges
<numeric>	Numeric operations on values in ranges
Strings library
<cstring>	Various narrow character string handling functions
<string>	std::basic_string class template
<string_view> (C++17)	std::basic_string_view class template
Text processing library
<cctype>	Functions to determine the category of narrow characters
<charconv> (C++17)	std::to_chars and std::from_chars
<clocale>	C localization utilities
<codecvt> (C++11) (deprecated in C++17) (removed in C++26)	Unicode conversion facilities
<cuchar> (C++11)	C-style Unicode character conversion functions
<cwchar>	Various wide and multibyte string handling functions
<cwctype>	Functions to determine the category of wide characters
<format> (C++20)	Formatting library including std::format
<locale>	Localization utilities
<regex> (C++11)	Classes, algorithms and iterators to support regular expression processing
<text_encoding> (C++26)	Text encoding identifications
Numerics library
<cfenv> (C++11)	Floating-point environment access functions
<cmath>	Common mathematics functions
<complex>	Complex number type
<linalg> (C++26)	Basic linear algebra algorithms (BLAS)
<numbers> (C++20)	Math constants
<random> (C++11)	Random number generators and distributions
<simd> (C++26)	Data-parallel types and operations on these types
<valarray>	Class for representing and manipulating arrays of values
Time library
<chrono> (C++11)	C++ time utilities
<ctime>	C-style time/date utilities
Input/output library
<cinttypes> (C++11)	Formatting macros, intmax_t and uintmax_t math and conversions
<cstdio>	C-style input-output functions
<filesystem> (C++17)	std::filesystem::path class and supporting functions
<fstream>	std::basic_fstream, std::basic_ifstream, std::basic_ofstream
<iomanip>	Helper functions to control the format of input and output
<ios>	std::ios_base class, std::basic_ios class template and typedefs
<iosfwd>	Forward declarations of all classes in the input/output library
<iostream>	Several standard stream objects
<istream>	std::basic_istream class template and typedefs
<ostream>	std::basic_ostream, std::basic_iostream
<print> (C++23)	Formatted output library including std::print
<spanstream> (C++23)	std::basic_spanstream, std::basic_ispanstream, std::basic_ospanstream class templates and typedefs
<sstream>	std::basic_stringstream, std::basic_istringstream, std::basic_ostringstream
<streambuf>	std::basic_streambuf class template
<strstream> (deprecated in C++98)(removed in C++26)	std::strstream, std::istrstream, std::ostrstream
<syncstream> (C++20)	std::basic_osyncstream, std::basic_syncbuf and typedefs
Concurrency support library
<atomic> (C++11)	Atomic operations library
<barrier> (C++20)	Barriers
<condition_variable> (C++11)	Thread waiting conditions
<future> (C++11)	Primitives for asynchronous computations
<hazard_pointer> (C++26)	Hazard pointers
<latch> (C++20)	Latches
<mutex> (C++11)	Mutual exclusion primitives
<rcu> (C++26)	Read-copy update mechanisms
<semaphore> (C++20)	Semaphores
<shared_mutex> (C++14)	Shared mutual exclusion primitives
<stop_token> (C++20)	Stop tokens for std::jthread
<thread> (C++11)	std::thread class and supporting functions

C compatibility headers

For some of the C standard library headers of the form xxx.h, the C++ standard library both includes an identically-named header and another header of the form cxxx (all meaningful cxxx headers are listed above). The intended use of headers of form xxx

With the exception of complex.h, each xxx.h header included in the C++ standard library places in the global namespace each name that the corresponding cxxx header would have placed in the std

These headers are allowed to also declare the same names in the std namespace, and the corresponding cxxx headers are allowed to also declare the same names in the global namespace: including <cstdlib> definitely provides std::malloc and may also provide ::malloc. Including <stdlib.h> definitely provides ::malloc and may also provide std::malloc

Notes: xxx.h headers are deprecated in C++98 and undeprecated in C++23. These headers are discouraged for pure C++ code, but not subject to future removal.

<assert.h>	Behaves same as <cassert>
<ctype.h>	Behaves as if each name from <cctype> is placed in global namespace
<errno.h>	Behaves same as <cerrno>
<fenv.h> (C++11)	Behaves as if each name from <cfenv> is placed in global namespace
<float.h>	Behaves same as <cfloat>
<inttypes.h> (C++11)	Behaves as if each name from <cinttypes> is placed in global namespace
<limits.h>	Behaves same as <climits>
<locale.h>	Behaves as if each name from <clocale> is placed in global namespace
<math.h>	Behaves as if each name from <cmath> is placed in global namespace, except for names of mathematical special functions
<setjmp.h>	Behaves as if each name from <csetjmp> is placed in global namespace
<signal.h>	Behaves as if each name from <csignal> is placed in global namespace
<stdarg.h>	Behaves as if each name from <cstdarg> is placed in global namespace
<stddef.h>	Behaves as if each name from <cstddef> is placed in global namespace, except for names of std::byte and related functions
<stdint.h> (C++11)	Behaves as if each name from <cstdint> is placed in global namespace
<stdio.h>	Behaves as if each name from <cstdio> is placed in global namespace
<stdlib.h>	Behaves as if each name from <cstdlib> is placed in global namespace
<string.h>	Behaves as if each name from <cstring> is placed in global namespace
<time.h>	Behaves as if each name from <ctime> is placed in global namespace
<uchar.h> (C++11)	Behaves as if each name from <cuchar> is placed in global namespace
<wchar.h>	Behaves as if each name from <cwchar> is placed in global namespace
<wctype.h>	Behaves as if each name from <cwctype> is placed in global namespace

Special C compatibility headers

The header <stdatomic.h> declares names which are also provided in the C standard library, and defines the _Atomic macro which is a keyword in C. Unlike other xxx.h headers, corresponding <cstdatomic>

<stdatomic.h> (C++23)

Defines _Atomic and provides corresponding components in the C standard library

Empty C headers

The headers <complex.h>, <ccomplex>, <tgmath.h>, and <ctgmath>

<ccomplex> (C++11) (deprecated in C++17) (removed in C++20)	Simply includes the header <complex>
<complex.h> (C++11)	Simply includes the header <complex>
<ctgmath> (C++11) (deprecated in C++17) (removed in C++20)	Simply includes the headers <complex> and <cmath>: the overloads equivalent to the contents of the C header tgmath.h
<tgmath.h> (C++11)	Simply includes the headers <complex> and <cmath>

Meaningless C headers

The headers <ciso646>, <cstdalign>, and <cstdbool>

<ciso646> (removed in C++20)	Empty header. The macros that appear in iso646.h in C are keywords in C++
<cstdalign> (C++11) (deprecated in C++17) (removed in C++20)	Defines one compatibility macro constant
<cstdbool> (C++11) (deprecated in C++17) (removed in C++20)	Defines one compatibility macro constant
<iso646.h>	Has no effect
<stdalign.h> (C++11)	Defines one compatibility macro constant
<stdbool.h> (C++11)	Defines one compatibility macro constant

Unsupported C headers

The C headers <stdatomic.h>,(until C++23) <stdnoreturn.h>, and <threads.h> are not included in C++ and have no cxxx

Experimental libraries

C++ TR's/TS's also define several collections of headers.

See also

C documentation for C Standard Library headers