The real value of the definitions comes in the form of concrete models that represent common computer systems-such as desktops,servers and printers - as well as network devices,including routers and switches.

• 这些定义的真实价值是在于以具体模型的形式，来表示公共的计算机系统，如台式机、服务器和打印机以及网络设备，包括路由器和交换器。