Interactivity

Interactivity?

In just a few years, the world wide web has progressed beyond almost all the other infomation delivery media. It has made it possible for the user to determine their route rather than being forced down the path envisaged by the author / designer / creator.. This is interactivity. The user interacts with the site and creates their own path or experience. It may be as simple as giving the user a choice as to which page they visit next, but true interactivity is where the site responds according to the input of the user. Thus it is possible to put games and quizzes on a web site and to integrate shopping carts and present real-time data to the website user.

Scripting (Javascript)

Scripting is a client-side technology. When a user's browser retrieves a web page from the server the code may have a script embedded within it. A script is a very simple (although to look at it you may disagree) piece of computer code.

Provided the browser supports javascript, the script instructs the browser to perform certain actions. This may be when the page loads or later, say when the mouse moves over a certain part of the page or a button is clicked.

At one time Microsoft introduced their own version of scripting, VBScript, however this seens to have been dropped in favour of the almost universal Javascript.

Not all browsers support javascript and with the growth of such things a GPRS phones with built in browsers not all devices are capable of supporting javascript.

Applets (Java)

Applets (the word means a mini application) are the next stage of proression on from scripts. They are a client side technology but require additional components, known as class files, to be downloaded from the server.

In addition it is necessary to have something called the java virtual machine (JVM) installed on the client computer. However this is usually installed on modern computers and can be downloaded and installed easily enough.

This is because java is capable of being run on any type of computer provided that a suitable JVM is installed. A different JVM is required according to the Operating system being run; i.e. Windows, Mac, Linux, Unix etc. but once installed then the downloaded class files will function identically irrespective of the computer they are run on.

Many modern mobile phones with web access have JVMs built in so it is even possible run applets on them too!

The advantage of an applet is that it is possible to do much more powerful things than it is possible to do with scripting. The applet is not bound to the web page and can respond to and interact with the computer without the user having to initiate each event.

Unfortunately, Java (the programming language for applets) requires programming skills. This means that you can't just start creating your own applets. Therefore, some programmers have created free applets that allow customization. So instead of learning the programming, people can simply use the already programmed applets and adapt the customizable parameters to meet their own requirements.

What's the difference between Java and JavaScript?

Despite the similarity in names, Java and JavaScript are two separate entities.

Java is a language designed by Sun Microsystems. Java scripts are precompiled into a compact form and stored on the server's side of the connection. HTML documents refer to the mini-applications known as Java "applets" by incorporating <APPLET> tags. Browsers that support the <APPLET> tag download the compiled Java applications and execute them.

JavaScript is a series of extensions to the HTML language designed by the Netscape Corporation and understood by Netscape Navigator versions 2.0 and higher, as well as by Microsoft Internet Explorer version 3.0 and higher (where it is called "JScript"). It's an interpreted language designed for controlling the browser; it has the ability to open and close windows, manipulate form elements, adjust browser settings, and download and execute Java applets.

Although JavaScript has a similar syntax to Java, it is quite distinct in many ways.

Flash

Flash is another client-side technology and requires the flash plug-in from Macromedia.

While animated GIFs can be used for animations, they do not support interactivity. They simply loop images in a predefined order and that's it. In Flash, you can control the animations. For example, you can make the animation stop and wait for the user to click a button. And when the animation starts again it can be dependant on which button was clicked.

Flash movies are in many ways similar to java applets. Small programs that can be embedded into your HTML pages. But unlike java applets, it is fairly easy to create animations in Flash without programming skills.

Sometimes, java programmers are not as skillfull as one might have wished. Some applets are programmed so they eventually take up all resources on the computer, and this results in "freezing" the browser.

So compared to java applets, the advantage of Flash is:

Flash movies are easier to create than java applets.

Flash movies are more stable in web browsers than java applets.

 

Note: While Flash has these advantages over applets, there is more to the story. There are things that you can program in java that just can't be done with Flash.

CGI

CGI? CGI programs? Programming? CGI is not actually a programming language- the three letters stand for Common Gateway Interface. CGI is another building block in web development, and yet another method of creating an interactive web site. It is the simplest, and most common, way to put dynamic content on a web site.

More simply, CGI is a method of passing information to a program intended to be run on the web.