Server-side scripts are used to extend the functionality of a Web server. For example, CGI scripts can be used to add interactivity to Web pages. CGI is not a programming language; but it is a specification for writing programs that enables transactions between a Web server and other programs on a server. Typical applications for CGI scripts include:

1. Interactive forms for handling data from a Web client, such as an order form
2. Searchable indexes of documents on the Web server
3. Page counters to track how many visitors a Web page receives

CGI scripts can be written with a procedural, object-oriented, or scripting language such as Perl.
Other functions that can be performed with a server-side script include:

Server APIs are proprietary extensions provided by the server vendors. Applications must be written in the language supported by the particular server. Examples of server APIs include NSAPI, which is from Netscape, and ISAPI, which is from Microsoft. Applications written to support a specific API have performance advantages; but they may need to be rewritten if the application is moved to a different type of server. In the next lesson, you will learn what technologies you can use to generate dynamic Web pages.