Wikipedia
TechWriter
TechWriter and EasiWriter are closed source proprietary word processor applications for RISC OS computers.
Essentially they have the same feature set, except that TechWriter has more features that are specifically aimed at Technical Writers such as the ability to edit mathematical formulae and insert Greek characters.
The default file format is proprietary; it is also possible since Version 8.9 to import Microsoft Word .docx documents and OpenOffice/ LibreOffice .odt files. It is also possible to save in TeX, HTML, and PDF format.