This document contains a list of features of RTEMS executive for RTOS comparison. The current snapshot of version 4.5+ was studied.

RTEMS is a real-time executive which provides a high performance environment for embedded critical and military applications including many features. RTEMS executive implements more API interface. One of them strictly adheres to POSIX® 1003.1b standard. Kernel creates multithread, multitasking environment for application threads. Each group of system functions is implemented by corresponding manager located in independent library module. Resulting application images are build by linking kernel libraries with application code. Set of used and linked manager modules can be defined independently for each application. There is support for TCP/IP networking, network and local filesystems. Debugging is possible over serial line or Ethernet.

There are enumerated most important POSIX API functions for each studied executive functionality. Other mentioned APIs have similar sets of functions.