Alt+F4 is the universal Windows keyboard shortcut to close the active application or window. Ctrl+4 and Alt+C have no standard close function, while Alt+Esc cycles through open windows rather than closing them. Alt+F4 works consistently across almost all Windows applications.
Alt + F4 is the standard Windows keyboard shortcut to close the currently active application or window. Alt + Esc cycles between open windows rather than closing them, and the other combinations aren't standard system shortcuts for closing applications.