Klipper can be used to set the behavior of the clipboard and selection in KDE.
The X Window System® uses two separate clipboard buffers: the “selection” and the “clipboard”. Text is placed in the selection buffer by simply selecting it, and can be pasted with the middle mouse button. To place text in the clipboard buffer, select it and press Ctrl+X or Ctrl+C. Text from the clipboard buffer is pasted using Ctrl+V or by selecting → .
In order to change clipboard/selection behavior, select from the Klipper pop-up menu, and in the dialog box that appears, select the General page. Unchecking Synchronize contents of the clipboard and the selection makes the clipboard and selection function as completely separate buffers as described above. With this option set, the option Ignore selection will prevent Klipper from including the contents of the selection in its clipboard history and from performing actions on the contents of the selection. Selecting Synchronize contents of the clipboard and the selection causes the clipboard and selection buffers to always be the same, meaning that text in the selection can be pasted with either the mouse button or the key combination Ctrl+V, and similarly for text in the clipboard buffer.