NAME

std::cin,std::wcin - std::cin,std::wcin

Synopsis

Defined in header <iostream>
extern std::istream cin; (1)
extern std::wistream wcin; (2)

The global objects std::cin and std::wcin control input from a stream buffer of
implementation-defined type (derived from std::streambuf), associated with the
standard C input stream stdin.

These objects are guaranteed to be initialized during or before the first time an
object of type std::ios_base::Init is constructed and are available for use in the
constructors and destructors of static objects with ordered initialization (as long
as <iostream> is included before the object is defined).

Unless sync_with_stdio(false) has been issued, it is safe to concurrently access
these objects from multiple threads for both formatted and unformatted input.

Once std::cin is constructed, std::cin.tie() returns &std::cout, and likewise,
std::wcin.tie() returns &std::wcout. This means that any formatted input operation
on std::cin forces a call to std::cout.flush() if any characters are pending for
output.

Notes

The 'c' in the name refers to "character" (stroustrup.com FAQ); cin means "character
input" and wcin means "wide character input"

Example

// Run this code

#include <iostream>
struct Foo {
int n;
Foo() {
std::cout << "Enter n: "; // no flush needed
std::cin >> n;
}
};
Foo f; // static object
int main()
{
std::cout << "f.n is " << f.n << '\n';
}

Possible output:

Enter n: 10
f.n is 10

See also

Init initializes standard stream objects
(public member class of std::ios_base)
cout writes to the standard C output stream stdout
wcout (global object)
stdin expression of type FILE* associated with the input stream
stdout expression of type FILE* associated with the output stream
stderr expression of type FILE* associated with the error output stream
(macro constant)