std:: cin, std:: wcin

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

#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';
}

Enter n: 10
f.n is 10

See also