Enable console output in a Windows program-2016.01.04

At some point, we may need to open the console window in the Win32 window application, print some messages, or act as another human-computer interface for the current program, or to help debug the program. To achieve this effect, you need to understand the function allocconsole and the Freopen function of C-runtime.
The AllocConsole function applies a console window for the current window program, and the following MSDN describes AllocConsole:

The allocconsole function allocates a new console for the calling process.

BOOL allocconsole (void);

The function call succeeds, returns a value other than 0, and returns 0 if the call fails.

After applying to the console for the current window program, we need to call C-runtime's Freopen function to relocate the standard output (stdout) to the new application's console.
The prototype of Freopen is as follows:

File *freopen (constcharconstchar *mode, file *stream);

where "conout$" is a special string that refers to the current console.

Example code:

if (AllocConsole ()) {                   "conout$""w+t", stdout );      " conout$ " " w+t " , stderr); }

Enable console output in a Windows program-2016.01.04