A History of Development on the Internet

Visual Basic programming technology represents a new set of approaches to Web technology, focused on the Visual Basic developer. This section offers a brief history of the Web's evolution from linked static content to the dynamic, compiled environment of Visual Basic Internet applications.

Static Content

The first applications on the Internet consisted of static pages that delivered their content to the browser and did not react dynamically to any actions the user performed. Although this model provides ready access to nicely formatted pages of information for your employees or potential customers, it provides limited interaction between the user and the Web server – and the static pages have to be manually edited to update their content.

Dynamic Content through Gateway Programming

The development of gateway interfaces such as Common Gateway Interface (CGI), Internet Server Application Programming Interface (ISAPI), and others allowed users to add dynamic content to the Web. With dynamic content, a browser can send a request for information. The server, instead of returning a static page, runs a script or application and returns HTML that reflects up-to-date, accurate information.

The disadvantage of gateway programs is that they are difficult to create and change. Gateway programs are not integrated into HTML files; in fact, they require an entirely different design process than do HTML files. In addition, all processing in a gateway program happens entirely on the server. This can increase server load and lead to backlogs in processing.

Scripting

Scripting enables dynamic content by embedding executable scripts directly in an HTML page. Rather than querying the server for an executable, the browser can process scripts as it loads the HTML page. These scripts can be processed on either the client or the Web server. The most common languages for client-side scripting are VBScript and JavaScript. A common framework used for server-side scripting is called Active Server Pages, or ASP.

In the ASP scripting model, HTML development and scripting development are part of the same process. This translates into tangible benefits, enabling Web providers to provide interactive business applications rather than merely publishing content. For example, a travel agency can go beyond just publishing flight schedules; it can use ASP scripting to enable customers to check available flights, compare fares, and reserve a seat on a flight.

With ASP scripting, you can use any scripting language for which an appropriate scripting engine is available. ASP supplies scripting engines for Microsoft Visual Basic Scripting Edition (VBScript) and Microsoft JScript. You can incorporate sophisticated functionality using ActiveX components to process data and generate useful information.

Date: 2016-05-25; view: 469; Нарушение авторских прав