The people behind Micro-Systems Software were Larry Studdard, Mark Lautenschlager, Steve Pagliarulo, and later Todd Tolhurst. According to a 1981 interview in 80-U.S. Journal, DOSPLUS came about indirectly when they were writing software for Larry Studdard’s sheet metal business. Steve Pagliarulo developed a number of patches to TRSDOS to deal with bugs they had encountered. That experience led Pagliarulo to write his own TRSDOS-compatible replacement operating system, which became the first version of DOSPLUS. That original version was never publicly released and was used only with their business software.

In 1980, Micro-Systems Software introduced DOSPLUS 3.0, the first publicly available version of DOSPLUS, for $99.95. The name “DOSPLUS” presumably identified it as an improvement to the Radio Shack DOS or as “DOS Plus.” Although not actually the third version, it used a 3.0 version number to show that it followed TRSDOS 2.3. Advertisements described it as “the fastest, most reliable, and easy-to-use operating system available.”]]> http://www.trs-80.org/dosplus/feed/ 2