// iostream_cerr.cpp
// compile with: /EHsc
// By default, cerr and clog are the same as cout
#include <iostream>
#include <fstream>
 
using namespace std;
 
void TestWide( ) 
{
 int i = 0;
 wcout << L"Enter a number: ";
 wcin >> i;
 wcerr << L"test for wcerr" << endl;
 wclog << L"test for wclog" << endl; 
}
 
int main( ) 
{
 int i = 0;
 cout << "Enter a number: ";
 cin >> i;
 cerr << "test for cerr" << endl;
 clog << "test for clog" << endl;
 TestWide( );
}
 
 

 Input 
 Sample Output 
Enter a number: 3
test for cerr
test for clog
Enter a number: 1
test for wcerr
test for wclogcout
 
The object controls insertions to the standard output as a byte stream.
 
cerr 
extern ostream cerr; 
The object controls unbuffered insertions to the standard error output as a byte stream. Once the object is constructed, the expression cerr.flags() & unitbuf is nonzero. 
 
cout 
extern ostream cout; 
The object controls insertions to the standard output as a byte stream.