TRON project
TRON ( The Real -time Operating system Nucleus ) is a real-time operating system, which was developed in 1984 by Ken Sakamura at the University of Tokyo. The TRON Project is not itself a source code or binaries available, but specifies only certain interfaces that must be met by any implementation, similar to the POSIX specification.
The interface description is freely available.
TRON is used in many embedded devices.
ITRON
ITRON (Industrial TRON ) is part of the TRON Project. It is a real-time operating system for consumer electronics products, which is mainly used by manufacturers from Asia for mobile phones. According to the Journal News Linux is the operating system most widely installed.
ITRON is based on the hardware specification T- Engine.
μITRON
The specification μITRON Version 2.0 was released in 1989. One of its characteristics is the limited functionality of the operating system kernel in order to use the lower range of 8 and 16 bit microprocessors. With version 3.0, the specification but was extended for 32-bit systems.