Active Server Pages (ASP) represents a significant advance in Web technology. This section offers a brief history of the Web's evolution from linked static content to the dynamic, interactive environment of ASP.
The Web’s origins lie in linked static content, and many sites today remain static: That is, you must manually edit your HTML pages in order to change what your Web server sends to a browser. In the static model, a browser uses the Hypertext Transport Protocol (HTTP) to request an HTML file from a Web server. The server receives the request and sends an HTML page to the browser, which formats and displays the page. Although this model provides ready access to nicely formatted pages of information for your employees or potential customers, it provides only limited interaction between the user and the Web server–and the static pages must be manually edited to update their content.
Gateway Interfaces such as Common Gateway Interface (CGI), Internet Server Application Programming Interface (ISAPI), and others can be used to add dynamic content to the Web. With these interfaces, a browser can send an HTTP request for an executable application rather than for a static HTML file. The server runs the specified application. The application can read information associated with the request to determine what values were passed with the request, such as those values that a user submits by filling out an HTML form. The application then parses the values for meaningful information and generates output in HTML to send to the browser. 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.
Note Although HTTP browsers and servers can transfer data formats other than HTML, such as Audio Video Interleaved (AVI) and Graphic Image Format (GIF), for the sake of simplicity, most of the discussion in this guide refers to content simply as HTML.
You can use ASP to include executable scripts directly in your HTML files. HTML development and scripting development become the same process, enabling you to focus directly on the look and feel of your Web site, weaving dynamic elements into your pages as appropriate. ASP applications are:
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.
ASP applications are easy to develop because you use ASP scripting to develop them. With ASP scripting, you can use any scripting language for which you provide the appropriate scripting engine. ASP supplies scripting engines for Microsoft® Visual Basic® Scripting Edition (VBScript) and JScript. You can incorporate sophisticated functionality using ActiveX server components, formerly known as Automation servers, to process data and generate useful information.
ASP-generated content is compatible with standard Web browsers.