std::cin,std::wcin(3)

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)