WordPerfect was originally written on, designed and used on
Data General's AOS and AOS/VS operating systems for their microcomputers (notably the MV series) by the WordPerfect Corp.
Mostly known for its word processing capabilities, WP, also included a spreadsheet and something like the first commercial groupware/scheduling software, WP Office. The typical user interface at that time would be a DG Dasher dumb terminal, 80/132 columns with something like 25 lines on a monochrome screen - and 16 function keys.
Then, the PC changed the landscape of data processing. Earlier systems, like office machines running CP/M and WordStar just did not come with the blessing of IBM - the IBM PC did. WP was ported to MS-DOS, but while the DG version was still maintained, newer developments like mouse support and graphics made it difficult to continue the product for AOS/VS. Also, CEO (Comprehensive Electronic Office), DG's office package, became more and more powerful, to finally take up most of WPs former market share on AOS/VS.
Wordperfect was later purchased by Novell, which built their groupware solution GroupWise, using features from WP office (and - indirectly, CEO), but failed to sell it successfully against Microsoft Word. Finally, WP was sold off to Corel.
A long-time favorite of writers, WordPerfect is now more or less history.