Commonly Found Internet File Types

1. Commonly Found Internet File Types The Internet provides access to many types of files, more than just HTML

2. Files • A file is a collection of data or information that has a name, called the filename. • Almost all information stored in a computer is in a file. Source: http://www.webopedia.com

3. File Types • There are many different types of files which store different types of data. • For example, program files store programs, and text files store text. • File types are identified by • their file extension • http://www.webopedia.com/quick_ref/fileextensions.asp • the programs that can create and interpret them.

4. File Types • Some of the types of files we will look at: • Text files • Image files • Audio files • Video & Animation files • Web page files • Program files

5. Text Files • Text files contain primarily character data • There are text files that can be created and interpreted by all text programs: • .TXT – Plain text (characters only) • .RTF – Rich text limited formatting + text • There are proprietary formatted text files, Word processor files, that require software • .DOC (Microsoft Word) • .WPD (WordPerfect)

6. Text Files • .PDF – The Portable Document Format by Adobe was created to provide a way to digitize printed text into a format that can be viewed on any computer platform. • This is a psuedo-text file

7. Text Files PDF • Files are created by scanning documents into bitmaps that act like photographs of the printed page. • PDF allows the document to keep its formatting, like word processing files, but eliminates the need for the user to poses the proprietary software that created it. • PDF files are searchable like text files.

8. Image Files • There are so many graphics formats that there is no true standard for the industry • For the Web, however, there are two file formats that every Web browser will support: • .GIF • .JPEG • There’s another graphic format emerging as a universal Web graphic type, supported by all newer web browsers & image editing software: • .PNG

9. Image Files • .GIF – Graphics Interchange Format • Invented & patented by CompuServe for use on computer networks • .JPG or .JPEG –Joint Photographic Experts Group • Named for the standards committee that formed it • Intended to be a platform-independent graphics format • .PNG – Portable Network Graphics format • The patent and license-free format approved by the W3C (World Wide Web Consortium) to replace the patented GIF format.

10. Image Files • .BMP –Windows bitmap. • The most efficient format to use with Windows. • .PICT – Macintosh Picture file • Understood by every graphics program that runs on the Mac • .PCD – Photo CD • Kodak’s graphics file format; • contains 5 sizes of each picture, “wallet” - “poster”

11. Audio Files • Every sound has a waveform that describes its frequency, amplitude, and harmonic content. • Waveform audio digitizers capture sound by sampling this waveform thousands of times per second; the samples are stored in a computer file.

12. Audio Files • .WAV – Windows sound file • Created by Microsoft & IBM • Contains a digital representation of analog • .MP3 – MPEG audio layer 3 • The most popular audio format on the Internet. • MP3 can compress CD audio into a substantially smaller-sized file without loosing sound quality.

13. Audio Files • .AU – Audio format from Sun • Format for sound files on UNIX machines • Prevalent on the internet because it is the audio file format for the Java programming language • .AIF, .AIFF, .AIFC – Audio Interchange File Format • A format for storing and transmitting sampled sound • Apple standard for Mac sound hardware. • AIFC is a more compressed file type than AIF.

14. Audio Files • .RA, .RAM – RealNetworks Audio (aka RealAudio) • Created for streaming on the Internet. • Uses a proprietary file format optimized for real-time transmission. • .MID, .MIDI –Musical Instrument Digital Interface • MIDI is a music synthesizer file format that requires very little bandwidth to transmit. • The file contains the commands for the sound card in a multimedia PC to interpret and generate the waveform

15. Video Files • When a movie gets digitized into a computer file, the digital data stream is enormous. To conserve file space and reduce the bandwidth required to transmit the movie, the video gets compressed.

16. Video Files • Video Compression Schemes • YUV sub sampling - Divides the screen into blocks and averages colors of the pixels in each square. • Delta frame encoding - Shrinks data by storing only the information that changes between frames; for example, if the background scene does not change, there is no need to store the scene again. • Run length encoding - Detects a “run” of identical pixels and encodes how many occur instead of recording each individual pixel.

17. Video Files • .AVI - Audio/Video Interleave • Windows video format • Uses a scheme in which audio frames are interleaved with the video. • .MOV, .QT –QuickTime • Originally for the Mac, but because of its cross-platform capabilities, has become very popular on the Internet.

18. Video Files • .MPG, .MPEG – Moving Picture Experts Groupformat • Emerging as the digital video standard for the US and much of the world. • Named for the International Standards Organization committee that created it. • .RM – RealNetworks Movies (aka RealVideo) • Uses the real-time streaming protocol (RTSP), a proprietary format that was invented for streaming audio and video over the Internet

19. Animation Files • Animation is the use of a computer to create movement on the screen. • There are several animation file types. Some of the most commonly found are: • Animated GIFs • Shockwave • Flash

20. Animation Files • .GIF – (Animated) GIFs • A special kind of GIF file that may combines multiple images into a single GIF file. The images are shown in a continual loop, to give the appearance of movement. • Supported by nearly all Web browsers • Files tend to be smaller than other animation files

21. Animation Files • .SWF – Shockwave • Created by Macromedia, it enables Web pages to include multimedia objects. • Files are created with the Director software • Browsers require a plug-in to run shockwave • Allows interaction with the user, accepting mouse clicks that can be programmed to cause an action

22. Animation Files • .FLA – Flash • Distributed by Macromedia • A bandwidth friendly and browser independent vector-graphic animation technology. • Browsers require a plug-in to run Flash

23. Web Page Files • .HTML, .HTM – Hypertext Markup Language • Actually a Text file containing text characters & ‘tags’ that can be interpreted by the browser

24. Web Page Files - HTML <html> <head> <title>Campus Map</title> </head> <body background="/graphics/bkgrnd2.gif" text="000000" link="BB22aa"> <p align="center"> <a HREF="/"><img src="../graphics/directions.gif" width="459" height="80" alt="Campus Map"></a> </p> <font size="+2" color="blue"><p align="center"> <br> Onondaga Community College Map </font> <br> <font size="-1"><a href="areamap.html">Directions</a> | <a href="key.html">Map Legend/Key</a> | <a href="listbldg.html">Building List</a> | <a href="altview.html">Alternate View</a> | <a href="east.html">East Side Zoom</a> | <a href="west.html">West Side Zoom</a> <br> <br> </font> <img src="map2b.jpg" alt="College Map" width="598" height="267"> <br> <br> </body> </html>

25. Web Page Files • .ASP – Active Server Pages • Microsoft technology combines HTML, Active X and JavaScript to create Web pages. • .CFM, .CFML – Cold Fusion pages • Allaire technology combines proprietary tags with HTML to create dynamic Web pages

26. Web Page Files • .CGI – Common Gateway Interface files • A standard that determines how a web server will gather information from a web page on a client. • Used with forms mostly • .CSS – Cascading Style Sheet File • A type of file used in Web page development that applies many features with a simple syntax. • CSS files are a collection of rules that apply to one or more HTML pages. A rule is a statement made up of an HTML or custom tag called selector, and its defined properties referred to as a declaration.

27. Internet File Type Reference http://www.udel.edu/interlit2/chapter12.html

28. Do Not Change A File’s Extension!!! • When you save a file you can change the name of the file. Be careful, however, not to rename the filename extension. • Remember that your computer looks at the filename extension to determine what application will be used to handle the file. Renaming the filename extension will only confuse your computer when you try to access the file.