Series 90 is completely incompatible with Series 60 and UIQ, the most popular platforms for Symbian smartphones. However, some applications from Nokia Series 80 Communicator devices – such as the Nokia 9300 – will function under Series 90.
Essentially, Series 90 is a development of the PsionEikonGUI as used on the Series 5, Series 5mx, Revo, netPad, Series 7 and netBook machines. It has been modified to be controlled entirely through the touchscreen, supplemented by the 77x0's seven hardware buttons and rocker-dial. The Nokia 7700, which was never released, had only an on-screen keyboard for text input; the 7710 added basic handwriting recognition. Applications now have only a single menu tree, accessible from the title bar at the top of the screen; there is no Exit or Quit option in most apps; and a button bar has been added to the right hand side of the screen, resembling that of the Nokia Communicator smartphones.