Standard library header <iostream>

 

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Standard library headers

Language support
<cstddef> <cstdlib> <version> (C++20) <limits> <climits>	<cfloat> <cstdint> (C++11) <stdfloat> (C++23) <new> <typeinfo>	<source_location> (C++20) <exception> <initializer_list> (C++11) <compare> (C++20)	<coroutine> (C++20) <csignal> <csetjmp> <cstdarg>
Concepts
<concepts> (C++20)
Diagnostics
<stdexcept> <stacktrace> (C++23)	<cassert>	<cerrno>	<system_error> (C++11)
Memory management
<memory>	<memory_resource> (C++17)	<scoped_allocator> (C++11)
Metaprogramming
<type_traits> (C++11)	<ratio> (C++11)
General utilities
<utility> <tuple> (C++11) <optional> (C++17) <variant> (C++17)	<any> (C++17) <debugging> (C++26) <expected> (C++23) <bitset>	<functional> <typeindex> (C++11) <execution> (C++17)	<charconv> (C++17) <format> (C++20) <bit> (C++20)
Strings
<string_view> (C++17) <string>	<cctype> <cwctype>	<cstring> <cwchar>	<cuchar> (C++11)
Containers
<array> (C++11) <deque> <forward_list> (C++11) <list>	<vector> <map> <set> <unordered_map> (C++11)	<unordered_set> (C++11) <queue> <stack> <flat_map> (C++23)	<flat_set> (C++23) <span> (C++20) <mdspan> (C++23) <inplace_vector> (C++26)
Iterators
<iterator>
Ranges
<ranges> (C++20)	<generator> (C++23)
Algorithms
<algorithm>	<numeric>
Numerics
<cfenv> (C++11) <complex>	<random> (C++11) <valarray>	<cmath> <linalg> (C++26)	<numbers> (C++20)
Time
<chrono> (C++11)	<ctime>
Localization
<locale>	<clocale>	<codecvt> (C++11/17/26*)	<text_encoding> (C++26)
Input/output
<iosfwd> <iostream> <ios> <streambuf>	<istream> <ostream> <iomanip> <print> (C++23)	<sstream> <spanstream> (C++23) <fstream> <syncstream> (C++20)	<filesystem> (C++17) <cstdio> <cinttypes> (C++11) <strstream> (C++98/26*)
Regular expressions
<regex> (C++11)
Concurrency support
<stop_token> (C++20) <thread> (C++11) <atomic> (C++11) <rcu> (C++26)	<stdatomic.h> (C++23) <mutex> (C++11) <shared_mutex> (C++14)	<condition_variable> (C++11)   <semaphore> (C++20) <latch> (C++20)	<barrier> (C++20) <future> (C++11) <hazard_pointer> (C++26)
C compatibility
<cstdbool> (C++11/17/20*)   <ccomplex> (C++11/17/20*)	<ctgmath> (C++11/17/20*)	<cstdalign> (C++11/17/20*)	<ciso646> (until C++20)

 

This header is part of the Input/output library.

Including <iostream> behaves as if it defines a static storage duration object of type std::ios_base::Init, whose constructor initializes the standard stream objects if it is the first std::ios_base::Init object to be constructed, and whose destructor flushes those objects (except for cin and wcin) if it is the last std::ios_base::Init object to be destroyed.

Includes
<ios> (C++11)	std::ios_base class, std::basic_ios class template and several typedefs
<streambuf> (C++11)	std::basic_streambuf class template
<istream> (C++11)	std::basic_istream class template and several typedefs
<ostream> (C++11)	std::basic_ostream, std::basic_iostream class templates and several typedefs
Objects
cinwcin	reads from the standard C input stream stdin (global object)
coutwcout	writes to the standard C output stream stdout (global object)
cerrwcerr	writes to the standard C error stream stderr, unbuffered (global object)
clogwclog	writes to the standard C error stream stderr (global object)

Synopsis

#include <ios>
#include <streambuf>
#include <istream>
#include <ostream>
 
namespace std {
  extern istream cin;
  extern ostream cout;
  extern ostream cerr;
  extern ostream clog;
 
  extern wistream wcin;
  extern wostream wcout;
  extern wostream wcerr;
  extern wostream wclog;
}

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 155	C++98	the type of the static object was std::basic_ios::Init (not strictly wrong, but the wording was misleading)	corrected to std::ios_base::Init
LWG 1123	C++98	including <iostream> did not guarantee the construction of std::ios_base::Init objects	guarantees