Computer Architecture
The computer system structure shown in FIG.
Typically, a computer system, the bottom level the machine attributes of the machine is often transparent to the programmer.
Composition of the computer
1. Series machine
The same means, the same manufacturers of the system architecture, but the composition and implementation of technologies for a range of different different types of machines. They each have different properties, using different composition and implementation techniques, but the programmer can see the properties of the machine are the same.
2. compatibles
Series machine from a programmer's point of view have the same machine attributes, so the machine language program compiled by the property as well as the compiler can be common to stall the machine, the machine is called stall software compatible.
computer network
1. Definition of the computer network
The different geographic locations having individual functions multiple computers machines external device, connected through a communication line, in the management and coordination of network operating systems, network management software and network communication protocols, and computer system resource sharing and transmission of information.
Which has a unique network address (IP) is the network node devices. The entire network consists of a number of network nodes.
Computer Network Category
1. In accordance with the geographical scope and the number of users of points: personal area networks, local area networks, metropolitan area networks, wide area networks.
(1) personal area network (PAN): allows the device around a person's communication.
(2) Local Area Network (LAN): the local area network coverage is typically a house, a building and the like.
(3) Metropolitan Area Network (MAN): Coverage is often a city.
(4) Wide Area Network (WAN): it's great coverage, often from the core city to form a large network. Small cities and large cities are connected, forming a large network of cities connected to each other. Covering China's satellite network is a wide area network.
2. Network transmission media can be divided into wired and wireless networks
(1) Wireless: wireless connection. The radio wave communication, microwave communication, satellite communication or the like.
(2) cable networks: wired connection. Coaxial cable, optical fiber, etc.
Computer network hardware
1. Network transmission media
(1) UTP: copper wire wound together by a plurality of pairs, each copper wires enclosed in a simple plastic sleeve;
It is a kind of twisted pair telephone line:
Bit transmission rate of 10 ~ 600Mbps, twisted pair cable is typically RJ-45;
(2) coaxial cable:
Two inner and outer conductors, the inner conductor may have a single or multiple strands of wire and are generally composed of a metal outer conductor composition prepared mesh, an insulating material between the inner and outer conductors;
CCTV is a kind of coaxial cable connection;
The maximum transmission distance of up to 500m;
(3) Fiber
由两层折射率不同的材料组成；
传送距离从几千米到几十千米；
不受电磁波干扰，传输距离远，速率高，但安装和维护困难；
（4）红外线
如电视遥控器
（5）微博
地面传输：需要中继站
微信传输：不需要中继站，但信号来回会产生延迟；
2.中继器
通过对数据信号的重新发送或者转发扩大网络传输的距离。
3.集线器
对接收到的信号进行再生放大和整形。
4.交换机
基于MAC（网卡的硬件地址）识别，完成封装转发数据帧功能；
5.路由器链接因特网中个局域网，广域网的设备。
网络拓扑结构
总线型拓扑结构：简单，易于实现，维护，扩充；故障检测难；使用最广泛，如信息管理系统，办公自动化系统；
星形拓扑结构：单节点不影响其他结点，但中心节点会影响整个网络；
环形拓扑结构：抗故障性好；任意节点出问题都将导致整个网络瘫痪；适用于局域网；
树形拓扑结构：易于扩张；对根节点依赖性大；适用于局域；
计算机网络体系结构
1.OSI参考模型
只要遵循OSI标准的一个系统就可以和世界上任何地方的，也遵循统一标准的其他任何系统进行通信。
OSI参考模型自下而上组成部分：
（1）物理层
（2）数据链路层
（3）网络层
（4）传输层
（5）会话层
（6）表示层
（7）应用层；
2.TCP/IP参考模型
3.计算机网络协议
OSI和TCP/IP参考模型的每一层都由众多的协议组成，这些层可以看成一个个协议簇。
常见的应用层协议有（1）HTTP超文本传输协议（2）FIP文件传输协议（3）DNS计算机域名系统（4）telnet远程登陆协议
云计算
1.云计算概述：云计算本质上是一种共享服务。
特点
（1）虚拟化技术（2）高性能（3）高可靠性（4）按需部署（5）动态可扩展性（6）低成本
云计算有三种服务模式（SaaS模式，PaaS模式，IaaS模式），四种部署方法（公有云，私有云，社区云，混合云），五个关键功能（按需自助服务，宽带网络接入，资源地，响应迅速，可测量服务）
2.云计算体系构架
物联网
1.可以把世界上不同国家、地区的人或物体联系在一起，使其彼此之间可以相互交流数据信息。
2.物联网的特征（1）全面感知（2）可靠传递（3）智能处理
3.物联网的关键技术：（1）射频识别技术（2）传感技术（3）网络和通信技术（4）智能的信息处理技术
参考文本链接：https://blog.csdn.net/hanzhen7541/article/details/79004840