WordStar interface left a large legacy, and many of its control-key command are still available (optionally or as the default) in other programs, such as the modern cross-platform word processing software TextMaker and many text editors running under MS-DOS, Linux, and other UNIX variants. Some Borland products, including the popular Turbo Pascal compiler, and Borland Sidekick, used a subset of WordStar keyboard commands, the former in its IDE and the latter in the "Notepad" editors. The TEXT editor built into the firmware of the TRS-80 Model 100 portable computer supported a subset of the WordStar cursor movement commands (in addition to its own). Home word processing software like Write&Set not only use the WordStar interface, but have been based on WordStar DOS file formats, allowing WordStar users who no longer have a copy of the application to easily open and edit their files. There are WordStar keyboard command emulators and keymappings, both freeware and shareware, for current versions of Microsoft Word. Popular modern word processing software WordPerfect can open or save to WordStar documents, enabling users to move back and forth. Add-ons and companion products MailMerge was an add-on program (becoming integrated from WordStar 4 onwards) which facilitated the merge printing of bulk mailings, such as business letters to clients. Two files were required: a data file, being a list of recipients stored in a non-document, comma-delimited plain ASCII text file, typically named Clients.dat (although WordStar had no requirement for a specific file extension). Each subsequent line of text in the file would be dedicated to a particular client, with name and address details separated on the line dedicated to a client by commas, read left to right. For example: Mr., Michael, Smith, 7 Oakland Drive, ... WordStar would also access Lotus123 spreadsheet files (*.wk1) for this data and if the data contained flags to start and stop WordStar processing the data then flags could be set so that certain 'clients' are omitted from the output stream. a master document containing the text of the letter, using standard paragraphs (a.k.a. boilerplate text) as required. These would be mixed and matched as needed, and where appropriate, paragraphs could be inserted through external reference to subordinate documents. The writer would insert placeholders delimited by ampersands into the master document, e.g., &TITLE&, &INITIAL&, &SURNAME&, &ADDRESS1&. In each copy of the letter the placeholders would be replaced with strings read from the DAT file.