DECwindows
DEC's graphical environment for VMS and Ultrix, one of the first commercial desktops built on X11.
DEC had helped fund Project Athena and bet on X early. DECwindows arrived in the late 1980s for both VMS and Ultrix, with a session manager, a window manager and bundled applications such as a calendar and file manager. Its toolkit was XUI, the X User Interface, built on Xt.
When the Open Software Foundation set out to produce a common toolkit, DEC contributed XUI, which together with HP's widgets became the basis of Motif — the UIL description language came along the same route. DEC then switched to Motif itself and sold the result as DECwindows Motif, a name that outlived both DEC and Compaq and still ships on OpenVMS.