A family of graphical operating systems developed by Psion for portable devices, primarily PDAs. The name EPOC came from epoch, the beginning of an era, but was backfitted by the engineers to "Electronic Piece Of Cheese". The first version, later known as EPOC16, was developed in the late 1980s and early 1990s for Psion's "SIBO" (SIxteen Bit Organisers) devices. All EPOC16 devices feature an 8086-family processor and a 16-bit architecture. EPOC16 is a single-user pre-emptive multitasking operating system, written in Intel 8086 assembler language and C and designed to be delivered in ROM. It supported a simple programming language called OPL and an IDE called OVAL.
EPOC16 was followed by EPOC32 in 1997.