Windows API

Do I have to create a window in a Windows API application (with WinMain)? What if my application runs in the background (a server)?

You can use the WinAPI functions while running the program in a standard console, that is, you don't need to make a window. If you want to run in background, you can use handles and then the ShowWindow() function to hide the console.

You could have simply tried it, of course And this would have been better posted under Windows Programming, if I'm not mistaken.

windows application run on several windows subsystems: console, windows, posix, whatever
http://msdn.microsoft.com/library/de...mplref_135.asp
http://msdn.microsoft.com/library/de...locconsole.asp

to run a application with main you have to specify subsystem console (it's the default to most compilers). To work with a gui, specify windows. With a gui, you can call AllocConsole() to create a console for your process.
http://msdn.microsoft.com/library/de...locconsole.asp
with a console app... it´s a bit harder to get rid of the console. I don´t know why

where's a small example - of course this syntax for pragma coment is Ms specific. I don't know the gcc version. Never tried it

A console app

Code:

#pragma comment(linker, "/SUBSYSTEM:CONSOLE")
#include <iostream>

int main(){
    std::cout<<"Hllo world!"<<std::endl;
    return 0;
}

a gui app

Code:

#pragma comment(linker, "/SUBSYSTEM:WINDOWS")
#include <windows.h>
int WinMain(HINSTANCE hc, HINSTANCE hp, LPSTR cmdln, int guicmd){
    MessageBox(GetDesktopHandle(),"hello world","hello world",0);
    return 0;
}

any process can run without any console or window.
Of course to kill it you have to go to Task Manager