Regarding the DoubleSpace context, Wikipedia helps (1): Sept 1991: Digital Research releases DR DOS 6.0 with AddStor's SuperStor disk compression. March 1993:

Regarding the DoubleSpace context, Wikipedia helps (1): Sept 1991: Digital Research releases DR DOS 6.0 with AddStor's SuperStor disk compression. March 1993: Microsoft introduces MS-DOS 6.0, the first with DoubleSpace disk compression June 1993: IBM announces PC DOS 6.1 November 1993: Microsoft MS-DOS 6.2, leapfrogging IBM's PC DOS 6.1 and with improved the stability of DoubleSpace. February 1994: Microsoft found guilty of patent infringement, and Stac Electronics guilty of trade secret theft. Microsoft MS-DOS 6.21, removing DoubleSpace. June 1994: After a judge ordered Microsoft to recall all unsold infringing products worldwide, Microsoft settled its dispute with Stac, and released MS-DOS 6.22, bringing back disk compression with internally developed DriveSpace, which is about 5% slower than DoubleSpace. An interesting detail: In the MS-Stac trial, "Stac’s lawyers showed a videotape of Microsoft Chairman Bill Gates" "at the unveiling of MS-DOS 6.0 in which he wore a T-shirt saying, “We came, we saw, we doubled,” to underscore the importance of the compression feature." (2) A second detail, the "trade secret theft" was: Stac was found "to have committed a trade secret violation by reverse engineering features of a beta version of MS DOS that they had gotten in confidence and then using the information they gained in making their own product." (3) 1) https://en.wikipedia.org/wiki/Timeline_of_DOS_operating_systems https://en.wikipedia.org/wiki/Timeline_of_DOS_operating_syst... 2) https://www.latimes.com/archives/la-xpm-1994-02-24-fi-26671-story.html https://www.latimes.com/archives/la-xpm-1994-02-24-fi-26671-... 3) https://lwn.net/Articles/134642/ https://lwn.net/Articles/134642/