I'm creating a window in C++ with that code:
HWnd = CreateWindow(wc.lpszClassName,
10, 10, 1000, 800, 0, 0, hInst, NULL);
You can add
WS_CAPTION | WS_SYSMENU | WS_MAXIMIZEBOX style.
If you want your window to be without caption then you will need to adjust window size manually to fit into desktop work area that you can query using