Series 40' s underlying operating system is called Intelligent System Architecture ( ISA), also called the Nokia Operating System ( NOS). Series 40 was introduced in 1999 with the release of the Nokia 7110.
It had a 96 × 65 pixel monochrome display and. Symbian originated from EPOC32, an operating system created by Psion in the 1990s.
In June 1998, Psion Software became Symbian Ltd.