WordStar is a word processor application, published by MicroPro International, originally written for the CP/M operating system but later ported to DOS, that enjoyed a dominant market share during the early to mid-1980s. Although Seymour I. Rubinstein was the principal owner of the company, Rob Barnaby was the sole author of the early versions of the program; starting with WordStar 4.0, the program was built on new code written principally by Peter Mierau.
WordStar was a text-based word processing program, meaning that it worked with files that were essentially text, with markup language-like formatting commands (such as the "dot commands"); this made the files relatively small. By contrast, most word processors today are code-based, and save their documents in much larger files.
WordStar was originally developed for CP/M in 1978. It was the most feature-rich and easy-to-use word processor available for this operating system, and became a de facto standard. In 1981 WordStar version 2.26 was bundled with the Osborne 1 portable computer. Notably, WordStar was the last commercial word processor supporting the CP/M operating system. Release 4, the final CP/M compatible version, was sold with 5.25 floppy disk as a default, and an 8" version as an option.
WordStar is no longer developed, maintained or sold by its owners; it is effectively abandonware. It is currently the property of Riverdeep, Inc., an education and consumer software company, which is now part of Houghton Mifflin Harcourt Learning Technology.