LINK : fatal error LNK1561: entry point must be defined ERROR IN VC++

Is this a console program project or a Windows project? I’m asking because for a Win32 and similar project, the entry point is WinMain().

1. Right-click the Project (not the Solution) on the left side.
2. Then click Properties -> Configuration Properties -> Linker -> System

If it says Subsystem Windows your entry point should be WinMain(), i.e.

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPWSTR lpCmdLine, int nShowCmd)
{
   your code here ...
}

Besides, speaking of the comments. This is a compile (or more precisely a Link) error, not a run-time error. When you start to debug, the compiler needs to make a complete program (not just to compile your module) and that is when the error occurs.

It does not even get to the point being loaded and run.