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K Desktop Environment
Otherwise known as KDE.
KDE is a desktop environment created for Unix-based systems. The free, open-source project has been developed for years by hundreds of developers and the source code is available here.
The Desktop Environment became popualr due to the GUI it offers Unix workstations and servers. The KDE GUI makes it easier for new Unix users to get a grasp on the complicated operating system by adding menus, toolbars, an application help system and the ability to add themes.
Finally, the KDE application development framework is famously very simple to work with, leading to a plethora of apps like KOffice.