This requirement was relaxed in Windows 8.1, allowing the Windows key to be placed on any bezel or edge of the unit, though a centered location along the bottom bezel is still preferred. On Windows 8 tablet computers, hardware certification requirements initially mandated that the Windows key be centered on the bezel below the screen, except on a convertible laptop, where the button is allowed to be off-center in a tablet configuration. On Microsoft's Entertainment Desktop sets (designed for Windows Vista), the Windows key is in the middle of the keyboard, below all other keys (where the user's thumbs rest). In laptop and other compact keyboards it is common to have just one Windows key (usually on the left). The key is predated by the ⌘ Command key on Apple computers in 1980 and the Meta key in LISP/ UNIX computers in 1970. Compared to the former layout, a Windows key was placed between the left Ctrl and the left Alt and another Windows key and the menu key were placed between the right Alt (or AltGr) and the right Ctrl key. Historically, the addition of two Windows keys and a menu key marked the change from the 101/102-key to 104/105-key layout for PC keyboards.
