KDE Software Compilation 4

KDE Software Compilation 4 (KDE SC 4) was the only series of the so-called KDE Software Compilation (KDE SC), first released in January 2008. The final release was version 4.14.3 in November 2014. It was the follow-up to K Desktop Environment 3. Following KDE SC 4, the compilation was broken up into basic framework libraries, desktop environment, and applications, which are termed KDE Frameworks 5, KDE Plasma 5, and KDE Applications, respectively. Major releases (4.x) were released every six months, while minor bugfix releases (4.x.y) were released monthly.

The series included updates to several of the KDE Platform's core components, notably a port to Qt 4. It contained a new multimedia API called Phonon, a device integration framework called Solid, and a new style guide and default icon set called Oxygen. It also included a new, unified desktop and panel user interface called Plasma, which supported desktop widgets, replacing K Desktop Environment 3's separate components.

One of the overall goals of KDE Platform 4 was to make it easy for KDE applications to be portable to different operating systems. This was made possible by the port to Qt 4, which facilitated support for non-X11-based platforms, including Microsoft Windows and Mac OS X. Versions 4.0 to 4.3 of KDE Software Compilation were known simply as KDE 4 – the name change being a result of the KDE project's re-branding to reflect KDE's increased scope.