Screen is the best software used for full-screen window manager that multiplexes a physical terminal between several processes, typically interactive shells using only one SSH sesion or only one console.
All screen commands are prefixed by an escape key, by default C-a (that’s Control-a, sometimes written ^a). To send a literal C-a to the programs in screen, use C-a a. This is useful when when working with screen within screen. For example C-a a n will move screen to a new window on the screen within screen.