CDE (for Common Desktop Environment) is a proprietary desktop environment for UNIX, based on the Motif toolkit. CDE was jointly developed by Hewlett-Packard, IBM, Novell and Sun Microsystems in The Open Group.
Until about 2000, CDE was considered the de facto-standard for UNIX desktops, but at that time, free software desktop environments such as KDE and GNOME were quickly becoming mature, and became almost universal on the GNU/Linux platform, which already had a larger user base than most commercial Unices in total. In 2001, commercial Unix vendors Hewlett-Packard (HP-UX) and Sun Microsystems (Solaris) announced that they would phase out CDE as the standard desktop on their workstations, in favor of GNOME.
However, in April 2003, HP has reportedly opted to return to CDE, as GNOME has not stabilised sufficiently for their preference. It has been suggested that the non-frozen APIs are the main complaint.