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My Unix World

不要迷恋Unix,Unix只是计算世界很小的一部分!

 
 
 

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GUI Terminal  

2009-02-02 03:07:18|  分类: graphics-basic |  标签: |举报 |字号 订阅

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当GUI用户界面成为不可阻挡的潮流之后,大概在90年代初期,Terminal也终于进入到了Graphical_terminals时期。到这个时期,小型机基本上已经成了Unix或类Unix的天下,PC方面开始被苹果和微软霸占,专用系统渐渐退出市场。Unix领域出现了X terminals;Windows方面出现了Citrix Systems的软件图像终端WinFrame,微软也自己提出了Terminal Services 方案;IBM大型机依然是字符终端。

显然,从胖度上,微软的RDP是最瘦的Client,更接近传统意义上的Terminal,X Server则就庞大的多,其他的CS系统,则更加肥胖,如浏览器和IM聊天工具,而更胖的Client,如网络游戏的客户端,其实与Web浏览器有类似的本质。

Windows Terminal Services现在更名为Remote Desktop Services,它是微软的terminal server ,基于 Remote Desktop Protocol (RDP),RDP使用TCP3389端口,端口号也可以通过注册表修改。它支持Remote Assistance和Remote Desktop 两种客户端。它在Server端生成位图,只是在显示的时候,不在Server本地显示,而是显示在Client,它更接近GUI终端的传统形象。

这类的东西还有很多,都很有意思,但我的时间不多,不能深入追究了,走马观花随便看看。还是对自己强调一下,不能想当然得把Thin Client一概想象成硬件机器。X Server是Thin Client,Firefox是Thin Client,QQ客户端是Thin Client,

其实对X Server有些误解,把它称为X Terminal或者X Image Browser 更恰当一些。事实上,完全可以将X Server与Web Browser进行类比,两者都是将程序逻辑返回的显示信心解码并显示出来。而且,完全可以把X Server看作是一个解释器,它不是Client,而是一个将图像信息解码的工具,经过它解码之后的像素点阵,才是Client。X Server可以对应多套程序。但它们也有大量不同,Web Browser有主动权,而X体系中,主动权在X Client;另外,X Server与Web Browser属于不同的层次,事实上,HTML信息流被Web Browser解码后生成X Lib协议的新编码,这些编码再由X Server解码,并生成位图点阵。而Remote Desktop则将位图点阵压缩传递解压,以改变位图的显示地点。最后,由硬件显示单元把这些信息显示出来。Remote Desktop应该与显示硬件位于相同的层次。

摘录Wikipedia Thin Client中的一段:

"Thin client" has also been used as a marketing term for computer appliances designed to run thin client software. The SMARTSTATION THIN CLIENT, NEC US110, IGEL Technology Universal Desktops, Wyse Winterms, Neoware's Appliances, Hewlett-Packard HP Compaq t-series, Chip PC Jack PC and Xtreme PC Series, SaaS style Nexterm, NEXterminal, Sabertooth TC , TC3ProjectACP's ThinManager Ready Thin Clients, X terminal, ClearCube, Koolu, ThinCan or web kiosk might be considered thin clients in this sense.

A more recent concept in this genre is 'Ultra Thin Client' technology – which takes the 'thin' concept one step further by running the connection client software (Citrix, Windows Terminal Services, telnet etc) directly from the appliance's hardware. This is a marked difference to legacy thin-client hardware architecture which ran an operating system, often Windows CE or Linux between the hardware and connection client software.[3][4]

The latest concept is a 'Zero Client' which is a hardware only appliance that runs no software at all and directly connects the user to a virtualized desktop. This approach completely eliminates the need to manage thin client software of any kind. Pano Logic introduced such a device in 2007.

特别地,关于X-Terminals

In computing, an X terminal is a display/input terminal for X Window System client applications. X terminals enjoyed a period of popularity in the early 1990s when they offered a lower total cost of ownership alternative to a full Unix workstation.

An X terminal runs an X server. (In X, the usage of "client" and "server" is from the viewpoint of the programs: the X server supplies a screen, keyboard, mouse and touchscreen to client applications.) This connects to an X display manager (introduced in X11R3) running on a central machine, using XDMCP (X Display Manager Control Protocol, introduced in X11R4).[1]

Thin clients have somewhat supplanted X terminals in that they are 'fattened' with added flash memory which contains software that duplicates much of the various Microsoft operating systems, thus acquiring the ability to "speak" a range of remote desktop protocols. Due to the existence of free software implementations of multiple protocols X terminals which do not have this extra flash memory have been commercially obsoleted by more general-purpose thin clients and by low cost PCs running an X server.

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