In computing, DOC or doc (an abbreviation of ‘document’) is a filename extension for word processing documents, most commonly in the proprietary Microsoft Word Binary File Format. Historically, the extension was used for documentation in plain text, particularly of programs or computer hardware on a wide range of operating systems. During the 1980s, WordPerfect used DOC as the extension of their proprietary format. Later, in the 1990s, Microsoft chose to use the DOC extension for their proprietary Microsoft Word format. The original uses for the extension have largely disappeared from the PC world.
Binary DOC files often contain more text formatting information (as well as scripts and undo information) than some other document file formats like Rich Text Format and HyperText Markup Language, but are usually less widely compatible.
The DOC files created with Microsoft Word versions differ. Microsoft Word versions up to Word 97 used a different format from Microsoft Word 97 – 2003.
In Microsoft Word 2007 and later, the binary file format was replaced as the default format by the Office Open XML format, though Microsoft Word can still produce DOC files.
Some historical documentations may use the DOC filename extension for plain-text file format. The DOC filename extension was also used in historical versions of WordPerfect for its proprietary format.
Some software applications use the name “DOC” in combination with other words (such as the name of software manufacturer) for different file formats. As an example, on the Palm OS, DOC is shorthand for PalmDoc, a completely unrelated format (commonly using PDB filename extension) used to encode text files such as ebooks.