What are File Types and File Formats?

Posted By BrokenClaw on November 5, 2007

A file on a computer is a distinct collection of data which is encoded in a particular way for its particular use. This special encoding is the file format. To the casual user, file formats are essentially invisible because they are automatically handled by the software they use. File formats can be divided into some basic categories, called file types. Examples of file types are:

The text file is the simplest type of computer file. It requires no special encoding and can be read by any computer because it contains only typed characters, like the output of a typewriter. All of the other file types are developed by software publishers, so the individual file format may be copyrighted. For example, a file from one word processor may not be readable by another word processor. This problem was especially true of old files, since modern programs are able to convert files from one to the other.

Every file has a name. In order for computer programs to recognize the file format, the name has two parts. The first part is its unique description, and the second part is the file extension. The two parts are separated by a period (pronounced dot). The file extension, which is usually only a few characters long, identifies the file format. It’s sort of like the two parts of a person’s name, where the file extension is the surname. Some examples of file names are:

  • interview.doc
  • vacation 2006.doc
  • instruction manual.pdf
  • building proposal.pdf
  • rosebush.jpg
  • grand-canyon015.jpg

Any file that has a file extension of .doc is a document file. A file with a .pdf extension is a portable document format, almost always known simply as a PDF. A file with a .jpg extension is an image file, pronounced jay-peg. The computer uses the file extension to identify the file format so it can use the correct program to open, or decode, the file. In many cases, the computer doesn’t display the file extension or ask you to assign it. For example, when you want to save a document or a photo, the program will prompt you to name the file, but it will encode the file in the proper format and add the extension itself.

There are many different file formats for image or photo files, such as .bmp, .tif, .gif, and .png. Over time, the .jpg has become the de facto standard for consumer products like digital cameras, cell phone cameras, and web applications. The same is true for audio files, with formats such as .wav, .aiff, and .wma. Today, the .mp3 file format is the one most often used in consumer products for voice and music.

The terms file type and file format are often used interchangeably, but the distinction is most evident when working with the video file type. Video is the most recent development in digital media, and no standard file format has risen to the top. Videos from a video camera or downloaded from the Internet come in a variety of formats, including .avi, .wmv, .mov, .mp4, and .divx. Each format requires special instructions, called a codec, to decode the file and play it on the computer. Users have to be aware of which formats their player, whether its on their computer or on a portable device, is able to play.


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