Alt+Space and Alt+Spacebar are keyboard shortcuts often used to open the window menu of the program currently open in Microsoft Windows.
How to use the Alt+Space keyboard shortcut
Alt+Space in Microsoft Windows
In addition to using the arrow keys in the window menu, you can also use its shortcuts, indicated by underline letters. For example, once displayed, R = Restore, M = Move, S = Size, N = Minimize, X = Maximize, and C = Close.
Related keyboard shortcuts and keys
Below are links to related keyboard shortcuts and individual key pages.