RTEMS

Real-Time Executive for Multiprocessor Systems (RTEMS), formerly Real-Time Executive for Missile Systems, and then Real-Time Executive for Military Systems, is a real-time operating system (RTOS) designed for embedded systems. It is free open-source software.

Development began in the late 1980s with early versions available via ftp as early as 1993. OAR Corporation is currently managing the RTEMS project in cooperation with a Steering Committee which includes user representatives.

Design

RTEMS is designed for real-time, embedded systems and to support various open API standards including POSIX and µITRON. The API now known as the Classic RTEMS API was originally based upon the Real-Time Executive Interface Definition (RTEID) specification. RTEMS includes a port of the FreeBSD TCP/IP stack as well as support for various filesystems including NFS and the FAT filesystem.

RTEMS does not provide any form of memory management or processes. In POSIX terminology, it implements a single process, multithreaded environment. This is reflected in the fact that RTEMS provides nearly all POSIX services other than those which are related to memory mapping, process forking, or shared memory. RTEMS closely corresponds to POSIX Profile 52 which is "single process, threads, filesystem".