For Internet browsers, a layout engine (also known as rendering engine) is a type of software that takes a web page's markup language such as HTML and formatting information like from CSS and displays the formatted content on the screen.  It is also known as the Internet's "painter."  We presented Gecko the last time, and this article now introduces its readers to Trident.

What is Trident?

Also known as MSHTML, Trident is a layout engine used for the Microsoft Windows version of Internet Explorer web browser.  It was introduced in October 1997, together with the release of Internet Explorer 4.0, and has been steadily upgraded and is still being used today.

Trident was designed as a software component in order to allow software developers to easily add web browsing functionality to their own applications. 

It also presents a component object model (or COM) interface that enables "interprocess communication" and dynamic object creation in any programming language, thus enabling developers to access and edit web pages in any COM-supported environment like C++ and .NET. 

For example, a web browser control can be added to a C++ program and Trident can then be used to access the page currently displayed in the browser and retrieve element values.

Applications of Trident

All versions of Internet Explorer, beginning at IE4, use Trident as its layout engine, and also used in a variety of other web browsers and software components. 

It is also used in file managers of Windows 98, Windows Me, and Windows 2000; as well as in the Add/ Remove Programs tool in Windows 2000 and Windows XP in rendering the list of installed programs. 

Trident-based applications can also be found in AOL Instant Messenger, EA Link, Google Talk, LimeWire, Maxthon, MSN Messenger, Microsoft Outlook, Netscape Browser, and Windows Media Player. 

Although Trident can be found in many models of Internet Explorer, it was not used in the IE5 version for Mac as well as in Internet Explorer Mobile.