java和internet計算機專業(yè)畢業(yè)設(shè)計外文翻譯-在線瀏覽
2025-03-05 03:01本頁面
【正文】 er to be processed. It could take many seconds or minutes to find out you had misspelled something in your request. Since the browser was just a viewer it couldn’t perform even the simplest puting tasks. (On the other hand, it was safe, because it couldn’t execute any programs on your local machine that might contain bugs or viruses.)To solve this problem, different approaches have been taken. To begin with, graphics standards have been enhanced to allow better animation and video within browsers. The remainder of the problem can be solved only by incorporating the ability to run programs on the client end, under the browser. This is called clientside programming.Clientside programmingThe Web’s initial serverbrowser design provided for interactive content, but the interactivity was pletely provided by the server. The server produced static pages for the client browser, which would simply interpret and display them. Basic HyperText Markup Language (HTML) contains simple mechanisms for data gathering: textentry boxes, check boxes, radio boxes, lists and dropdown lists, as well as a button that can only be programmed to reset the data on the form or “submit” the data on the form back to the server. This submission passes through the Common Gateway Interface (CGI) provided on all Web servers. The text within the submission tells CGI what to do with it. The most mon action is to run a program located on the server in a directory that’s typically called “cgibin.” (If you watch the address window at the top of your browser when you push a button on a Web page, you can sometimes see “cgibin” within all the gobbledygook there.) These programs can be written in most languages. Perl has been a mon choice because it is designed for text manipulation and is interpreted, so it can be installed on any server regardless of processor or operating system. However, Python (my favorite—see ) has been making inroads because of its greater power and simplicity.Many powerful Web sites today are built strictly on CGI, and you can in fact do nearly anything with CGI. However, Web sites built on CGI programs can rapidly bee overly plicated to maintain, and there is also the problem of response time. The response of a CGI program depends on how much data must be sent, as well as the load on both the server and the Internet. (On top of this, starting a CGI program tends to be slow.) The initial designers of the Web did not foresee how rapidly this bandwidth would be exhausted for the kinds of applications people developed. For example, any sort of dynamic graphing is nearly impossible to perform with consistency because a Graphics Interchange Format (GIF) file must be created and moved from the server to the client for each version of the graph. And you’ve no doubt had direct experience with something as simple as validating the data on an input form. You press the submit button on a page。 the data is shipped back to the server。 you must then back up a page and try again. Not only is this slow, it’s inelegant.The solution is clientside programming. Most machines that run Web browsers are powerful engines capable of doing vast work, and with the original static HTML approach they are sitting there, just idly waiting for the
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