It started life as EPOC32, the operating system for "palmtop" devices made by UK-based Psion in the mid-90s; then Nokia and Ericsson decided they needed a smartphone OS that isn't Microsoft and bought into EPOC creating Symbian sometime around 1998. It took a while for Symbian to get off the ground because the hardware wasn't there yet and the partners kept bickering, but by 2006 it was shipping on a hundred million devices and was perceived as very successful against Microsoft's Windows Mobile. A few years later, Symbian would be trounced to oblivion by iOS and Android.

The interesting thing about Symbian was that it had a rich native framework but wasn't even close to POSIX or Windows. You didn't even get the C standard library; instead the system was built on an idiosyncratic embedded-centric dialect of '90s C++. This focus on optimization at expense of programmer convenience turned out to be a total dead-end once PC-style operating systems became viable on phones — but at least it made for a distinctive development experience.