Computer applications that need to store and work with large amounts of data typically use one of the data formats described above. There are also other data formats, but these are the most common. Data compression is very important in many cases. For example, files that consist of only a few characters will not be as readable on a personal computer as they would be on a cellular telephone. Even a short snippet of a long e-mail message will take much longer to download than it would on a standard phone or the Internet.
Data Format. A data file format is a specific vocabulary or set of instructions for encoding a particular set of data. Typically, the most commonly used data formats are XML, CSV, XHTML, and ASCII text. XML is an open standard, while others (such as HTML) are more commonly used. However, HTML is susceptible to malicious scripting and can be changed by unscrupulous Web sites.
Computer programs use data formats to tell them what the data is. This information can be stored in files on the hard drive, or in computer files known as input data formats, and output data formats, such as output ports. Computer programmers use a variety of data formats to control how their programs work. One example of input data formats is the Windows keyboard layout, which determines how your computer displays the letters on your screen.
Directory-Based Formats. Directory-based data formats are collections of one or more data sources. These data sources can be directories, web pages, software modules, audio and video data, user manuals, and so on. One example of a directory-based format is the Winamp folder structure, which allows the user to organize music files into folders.
Proprietary Formats. A proprietary format is an encoding format that has not been standardized. This means that all the data that it exposes can only be read or written by a program that is compatible with the encoding. The file extensions for proprietary formats vary from one generation to another. One example of a proprietary format is the GIF image format, which has no resemblance to the common GIF file extension used by computers and other computer applications.
Universal File Formats. Universal file formats are universally accepted data formats that can be loaded by computers and other electronic devices without any kind of compatibility issues. These file formats may include, among others, JPEG, GIF, PNG, TIFF, BMP, and WAHD. The size of the file is not a major concern in digital images. Thus, digital images that are stored in these file formats may be viewed on any normal computer system, including computers running Windows.
Portable Content-Type. Portable content-type (PCF) is a subset of the data formats described above. Portable content-type files are usually short files that can be compressed and transferred easily. PCF files are often used for storing short information, such as meta-tags and directory names.
A data format and its printer definition give a developer the ability to create documents in a certain data structure. When developing web applications, a developer needs to select the most appropriate data formats and printer definitions from the wide collection of data formats. Selecting a data format and printer definition may prove to be challenging for some developers because there are so many formats available. To make things easier, software like the Adobe Flash Writer and Adobe Acrobat Reader make it possible to develop documents in various data formats by combining a data format and a printer definition.