Files with the WSD extension are WordStar documents, and these files can be opened as of this writing by using the Corel WordPerfect Office X6 application. These WSD files are classified as text files and contains text with limited layout formatting attributes and text layout elements. Micropro International developed the WordStar word processing application for the Microsoft DOS (Disk Operating System) environment. This application was widely used in the 80s as among the most popular word processing programs at that time. Micropro International has abandoned further development and support for the WordStar application. Integrated into WordStar is the WYSIWYG editor, particularly the version developed for Microsoft DOS platforms. These WSD files and the WordStar word processing software were outdone in terms of usability and popularity in the mid 80s by the WordPerfect version 4 application, which is another old word processing software, primarily because WordPerfect 4.x integrated more features into its text and layout formatting options than WordStar and any other word processing application for the MS DOS environment at that time.