WMLScript Primer

WMLScript Primer

In this column we introduce a special dialect of JavaScript called WMLScript. The WMLScript language is part of the industry-wide standard for wireless applications called Wireless Application Protocol (WAP). The WAP includes one more language besides the WMLScript, the Wireless Macro Language (WML), which is the equivalent of HTML for wireless applications. We have covered the basics of WML in our previous column, Introducing WML and WMLScript.

WMLScript is based on JavaScript, but it has been modified to better support low bandwidth communication and thin clients. Several changes to the language were made in order accomplish that. First, WMLScript can be compiled to a bytecode, speeding up the interpretation by the user agent. Secondly, it is a procedural language and it supports locally-installed standard libraries of WMLScript procedures. Finally, it does not support some of the more advanced features of JavaScript that are heavy on computational and bandwidth needs.

The purpose of this column is two fold. The wireless world is getting more popular every day, and the number of programmers working for its businesses will rise over the next few years. Some of us will have to retool our JavaScript knowledge to WMLScript expertise, and this column is a good start to ramp up on the technology. The second motivation is to acquaint you with a superset of JavaScript. WMLScript demonstrates some of the future directions that JavaScript may go to. The column also emphasizes, by contrast, what's missing from JavaScript in comparison to other high-level programming languages such as C++.

In this column you will learn:

• How to call WMLScript libraries
• How to use WMLScript literals and operators
• How to construct compilation units and pragmas
• How to read the Mortgage example
• How to read a bytecode
• How to identify differences between WMLScript and JavaScript

Next: How to call WMLScript libraries