C: A programming language used mainly to create operating systems.

C++: A newer, object-oriented version of C. With object-oriented programming (OOP), entities are represented as self-contained objects with their own abilities ("methods") and pieces of information ("properties").

Java: A simplified version of C++, but with added facilities such as graphics.

Java Applets are designed to run within web pages.

• Each occupies a given rectangular space in the page.
• Similar to graphics, except they offer all the features of a program i.e. they are dynamic and you can interact with them.
• They can play video files, audio files and handle real-time data feeds.
• Developed by Sun Microsystems.
• Microsoft's version of Java applets is called ActiveX. Requires a special plug-in.
• Java programs can also be written in the form of stand-alone applications.

JavaScript (note the capital "S")

• Programs written within a web page itself, give more control over them than just HTML.
• Web pages are event-driven - they only react when something happens, like a mouse click. JavaScript works the same way.
• Developed by Netscape.
• Microsoft's produced a stripped down version of JavaScript called JScript. Often incompatible with JavaScript.

Visual Basic Script (VBScript)

• Object-based web page scripting language based on the Microsoft programming language Visual Basic.
• Can manipulate HTML objects such as radio buttons, check boxes and password fields, and ActiveX controls.

Java and ActiveX allow information to be downloaded and run on your system. Browsers therefore allow both of these to be disabled.

Plug-ins are programs developed to run in conjunction with web pages. If a web page needs you to have a plug-in in order to display properly it will prompt you to download it to your machine. The download can then be used whenever the page is revisited.

Plug-ins can be

• Full-screen - The plug-in fills the entire screen.
• Embedded - The plug-in occupies a rectangle within a web page (similar to applets).
• Hidden - The plug-in remains invisible and works in the background (e.g. MIDI player for music files).

Examples:

• Macromedia Flash creates animations using vector graphics in web pages.
• Macromedia Shockwave displays interactive games and multimedia user interfaces.
• Apple Quick Time plays movies files with the .mov extension.

Plug-ins can be installed online (browser still open) or offline (after browser has closed).

Lossy compression: Compressing data such as pictures resulting in some (imperceptible) loss of detail.

Lossless compression: Compressing data so that no detail is lost. The original data can be recreated perfectly.

Viewer: A program that allows you to view particular types of file available on the net (i.e. not web pages).
They are versions of fully-functioning programs that allow you to view files but not create them.

Examples:

• Microsoft PowerPoint Viewer allows you to view downloaded PowerPoint files.
• Adobe Acrobat Reader allows you to view Portable Document Format (PDF) files.

Video file formats:

.avi	Audio Video Interleave files play using the Windows Media Player.
.mov	The standard format for QuickTime movies and the native format on the Macintosh
.mpg or .mpeg	Moving Pictures Expert Group format is the standard format for movies on the web
.qt	Another format for QuickTime movies
.ram	Video file format for RealTime streaming video

Sound file formats:

.au	Format used by UNIX servers, but most browsers can handle them
.aiff	Audio Interchange File Format, developed by Apple
.mp3	MPEG-1 Audio Layer-3 compress audio files to a small size. Windows 98/ME/2000/XP have built-in MP3 players. Developers pay a licence fee to make use of the MP3 format.
.ogg	Ogg Vorbis is a free alternative to the MP3 format (no licence needed)
.ra	RealNetworks proprietary streaming audio format. Requires RealPlayer to play them
.wav	Waveform files are the native sound format for Windows. Most browsers can play these.

For Graphic file formats, see the Graphics and Images topic

Document formats:

.txt	Plain unformatted text (ASCII text)
.pdf	Portable Document Format files can be read on any computer possessing the Acrobat reader, regardless of operating system
.doc	Microsoft Word files
.eps	Encapsulated PostScript files allow you to move graphics between operating systems. Based on the PostScript language used to drive printers.
.rtf	Rich Text Format developed by Microsoft. Plain text with some embedded formatting commands. An almost universal format. Many WPs (e.g. Microsoft Word) can save in RTF, but the files can be very large.

Downloading files using a browser:

• Use Save As on the File menu of the browser to save the entire page.
• Right-click a graphic and use Save Picture/Image to save individual graphics.
• Text and images on a web page can be Copied and Pasted into programs such as Word.
• Beware of copyright infringement! Copyright laws apply on the net as well!

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