Network operating systems (NOSs) are operating systems that provide support for computer networking in addition to traditional hardware support. These were an important sub-class of conventional operating systems from the 1980s into the 1990s during the introduction of the early local area network (LAN) systems. As personal computers grew in power, NOSs were replaced by server software running on conventional operating systems. Today, NOSs are found primarily in dedicated networking hardware like routers.