WPD, WordPerfect Document File (.wpd)
The WPD Document file format
The text file format WPD was created in 1980 for the Corel WordPerfect word processing software by Satellite Systems International. In the 80's and early 90's, WordPerfect has been one of the most popular word processing programs and gathered a huge amount of admirers even until today. The software has been acquired in 1996 by Corel. Even though files with the WPD extension are associated with WordPerfect, most versions of Microsoft Word and OpenOffice writer are able to process and open WPD documents.
Technical details of WPD files
The prime usage of WPD files was to process formatted text only. Thus, those files contain chunks of text. Formatting information is stored via tags that WordPerfect recognizes as pieces of code. This makes detecting formatting errors a lot easier, since the program highlights sections in the text and reveals the inherit formatting. Similar to more common word processing file type like DOC, WPD files can embed information from external sources like spreadsheets, databases, or templates.