The Psion 3, 3A, 3C and 3MX ran EPOC, a proprietary 8086 OS with preemptive multitasking and a full keyboard-only GUI.
But their successors, the Psion 5, 5MX and netBook, ran a rewrite called EPOC32. That was written in C++, is native to ARM, and ran well in 4MB and very well in 8MB. Full preemptive multitasking, touchscreen GUI, networking, IPv4 and more, FAT32 and networking support.
That later was rebranded as Symbian and was the first mass-market smartphone OS. It was the only smartphone OS that could run the GSM comms stack on the same CPU as the user facing GUI OS -- its realtime support was that good. iOS, Android, WinCE, all need a separate CPU with its own RTOS for that.
It's a crime and a tragedy that nobody's picked it up and ported it to any modern SOC. It is much richer and more complete than any other modern C++ OS such as Genode or Serenity OS.
The Psion 3, 3A, 3C and 3MX ran EPOC, a proprietary 8086 OS with preemptive multitasking and a full keyboard-only GUI.
But their successors, the Psion 5, 5MX and netBook, ran a rewrite called EPOC32. That was written in C++, is native to ARM, and ran well in 4MB and very well in 8MB. Full preemptive multitasking, touchscreen GUI, networking, IPv4 and more, FAT32 and networking support.
That later was rebranded as Symbian and was the first mass-market smartphone OS. It was the only smartphone OS that could run the GSM comms stack on the same CPU as the user facing GUI OS -- its realtime support was that good. iOS, Android, WinCE, all need a separate CPU with its own RTOS for that.
Symbian is now 100% FOSS.
https://github.com/SymbianSource
It's a crime and a tragedy that nobody's picked it up and ported it to any modern SOC. It is much richer and more complete than any other modern C++ OS such as Genode or Serenity OS.