Data file format

The layout of a file in terms of how the data within the file are organised. A program that uses the data in a file must be able to recognise and possibly access data within the file. A particular file format is often indicated as part of a file's name by a filename extension (suffix). Conventionally, the extension is separated by a period from the name and contains three or four letters that identify the format. 

There are as many different file formats as there are different programs to process the files. Examples include: Word documents (.doc), Web text pages (.htm or .html), Web page images (.gif and .jpg), Adobe Postscript files (.ps), Adobe Acrobat files (.pdf), Executable programs (.exe), Multimedia files (.mp3 and others). 

Preferred formats are those designated by a data repository for which the digital content is maintained. If a data file is not in a preferred format, a data curator will often convert the file into a preferred format, thus ensuring that the digital content remains readable and usable. Usually, preferred formats are the de facto standard employed by a particular community. 

- CASRAI Dictionary

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