TheSeries 90 (S90, formerlyHildon) is aplatform formobile phones that use theSymbianoperating system (OS). It was developed byNokia together withPsion. It was released in 2003 and was to be the platform for theNokia 7700 which was cancelled, but S90 made it to market eventually in theNokia 7710.

Nokia discontinued Series 90 as a platform, but merged its technology intoS60.^[1][2] Although only one production Series 90 device was made, a form of thegraphical user interface (GUI) continued on as Nokia'sHildonuser interface in theMaemo shipped withNokia Internet Tablets.

Series 90 is fully incompatible withSeries 60 (S60) andUIQ, the most popular platforms for Symbiansmartphones. However, some applications from NokiaSeries 80 Communicator devices, such as theNokia 9300, will function under Series 90.

Essentially, Series 90 is a development of thePsionEikon GUI as used on theSeries 5, Series 5mx,Revo, netPad,Series 7 andnetBook machines. It has been modified to be controlled entirely through the touchscreen, supplemented by the 77x0's seven hardware buttons and rocker-dial. TheNokia 7700, which was never released, had only an on-screen keyboard for text input; the7710 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.

• Nokia platforms
• Smartphones

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