Netware Input/Output Subsystem NIOS <operating system, networking> (NIOS) The lowest {layer} in the {Novell NetWare} {client} architecture. NIOS is the interface layer between the client operating system and the 32-bit client services provided by NetWare. (http://developer.novell.com/research/appnotes/1996/november/01/04.htm). (1999-04-24)