All operating systems (OSs) in this category support TRON standards fully or partly. TRON is an acronym for: The Real-time Operating system Nucleus. The TRON Project officially began June 1984, due to findings and recommendations in a report by a Japan Electronic Industrial Development Association technical committee that investigated microprocessor uses in the 1990s and later. Dr. Ken Sakamura, University of Tokyo, chaired this committee, managed TRON development, and is the main creator of the TRON architecture.

Much like POSIX, TRON is not a body of computer code that is compiled and run on a processor. Rather, it is a set of standards: interfaces, design guidelines, software design specifications, for creating the computer code that will become an OS kernel, and defining language interfaces between an OS and its programs, to give compatibility when moving programs between compatible systems.

Much like Open Source software, all TRON standards are copyrighted (by the TRON Association), but available for use by software and hardware developers anywhere in the world for free. Thus the computer architecture based on it, the TRON Architecture, is an open architecture that invites and welcomes cloning and interoperability.

Unlike other modern kernels developed to date, TRON was proposed and designed via a top-down approach to serve as a common software core for all the varied types of computer systems used throughout human society and human living spaces. Since one real-time kernel cannot run across everything from an 8-bit one-chip microcontroller to a mainframe computer central processing unit, there are many versions of the TRON software core that have been defined to meet the needs of varied systems. Together, all variants, which are all compatible with each other, form the basis for the world's first "total computer architecture." It was also designed to meet the needs of high-speed networking, to form the basis of a highly efficient realtime network architecture.