单项工程综合概算包括设备购置费用和设备安装工程概算两部分。()
参考答案:错
结构化开发生命周期法是采用什么方法形成整个系统的信息模型的______
A.自顶向下
B.自底向上
C.自顶到底
D.自上到下
Networks can be interconnected by different devices. In the physical layer networks can be connected by (31) or hubs, which just move the bits from one network to an identical network. One layer up we find bridges and switches which operate at data link layer. They can accept (32) , examine the MAC address and forward the frames to a different network while doing minor protocol translation in the process. In network layer, we have routers that can connect two networks. If two networks have (33) network layer, the muter may be able to translate between the packer formats. In the transport layer we find transport gateway, which can interface between two transport connections. Finally, in the application layer, application gateways translate message (34) . As an example, gateways between Internet e-mail and X.400 e-mail must (35) the e-mail message and change various header fields.
A.syntax
B.semantics
C.language
D.format