RTEMS is a free open source

Open source

The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...

 real-time operating system

Real-time operating system

A real-time operating system is an operating system intended to serve real-time application requests.A key characteristic of a RTOS is the level of its consistency concerning the amount of time it takes to accept and complete an application's task; the variability is jitter...

 (RTOS) designed for embedded system

Embedded system

An embedded system is a computer system designed for specific control functions within a larger system. often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. By contrast, a general-purpose computer, such as a personal...

s.

The acronym RTEMS initially stood for Real-Time Executive for Missile Systems, then became Real-Time Executive for Military Systems before changing to its current meaning. RTEMS development began in the late 1980s with early versions of RTEMS 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.

RTEMS is designed for real-time, embedded systems and has been ported to various target processor architectures:

• ARM
  ARM architecture
  ARM is a 32-bit reduced instruction set computer instruction set architecture developed by ARM Holdings. It was named the Advanced RISC Machine, and before that, the Acorn RISC Machine. The ARM architecture is the most widely used 32-bit ISA in numbers produced...
  
  
• Atmel AVR
  Atmel AVR
  The AVR is a modified Harvard architecture 8-bit RISC single chip microcontroller which was developed by Atmel in 1996. The AVR was one of the first microcontroller families to use on-chip flash memory for program storage, as opposed to one-time programmable ROM, EPROM, or EEPROM used by other...
  
  
• Blackfin
  Blackfin
  The Blackfin is a family of 16- or 32-bit microprocessors developed, manufactured and marketed by Analog Devices. The family is characterized by their built-in, fixed-point digital signal processor functionality supplied by 16-bit Multiply–accumulates , accompanied on-chip by a small and...
  
  
• Freescale ColdFire
  Freescale ColdFire
  The Freescale ColdFire is a microprocessor that derives from the Motorola 68000 family architecture, manufactured for embedded systems development by Freescale Semiconductor .-Instruction set:...
  
  
• Texas Instruments
  Texas Instruments
  Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...
  
   C3x/C4x
  Texas Instruments TMS320
  Texas Instruments TMS320 is a blanket name for a series of digital signal processors from Texas Instruments. It was introduced on April 8, 1983 through the TMS32010 processor, which was then the fastest DSP on the market....
  
   DSPs
• H8/300
  H8 Family
  H8 is the name of a large family of 8-bit and 16-bit microcontrollers made by Renesas Technology, originating in the early 1990s within Hitachi Semiconductor and still actively evolving as of 2006...
  
  
• Intel 80386
  Intel 80386
  The Intel 80386, also known as the i386, or just 386, was a 32-bit microprocessor introduced by Intel in 1985. The first versions had 275,000 transistors and were used as the central processing unit of many workstations and high-end personal computers of the time...
  
  , Pentium, and above members of the x86 architecture
  X86 architecture
  The term x86 refers to a family of instruction set architectures based on the Intel 8086 CPU. The 8086 was launched in 1978 as a fully 16-bit extension of Intel's 8-bit based 8080 microprocessor and also introduced segmentation to overcome the 16-bit addressing barrier of such designs...
  
  
• Lattice Mico32
• 68k
  68k
  The Motorola 680x0/m68000/68000 is a family of 32-bit CISC microprocessors. During the 1980s and early 1990s, they were popular in personal computers and workstations and were the primary competitors of Intel's x86 microprocessors...
  
  
• MIPS
  MIPS architecture
  MIPS is a reduced instruction set computer instruction set architecture developed by MIPS Technologies . The early MIPS architectures were 32-bit, and later versions were 64-bit...
  
  
• Nios II
  Nios II
  Nios II is a 32-bit embedded-processor architecture designed specifically for the Altera family of FPGAs. Nios II incorporates many enhancements over the original Nios architecture, making it more suitable for a wider range of embedded computing applications, from DSP to system-control.Nios II is...
  
  
• PowerPC
  PowerPC
  PowerPC is a RISC architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM...
  
  
• Renesas M32C
• Renesas M32R
  M32R
  The M32R is a 32-bit RISC instruction set architecture developed by Mitsubishi for embedded microprocessors and microcontrollers. The ISA is now owned by Renesas Electronics Corporation, and the company designs and fabricates M32R implementations. M32R processors are used in embedded systems such...
  
  
• Renesas SuperH
  SuperH
  SuperH is a 32-bit reduced instruction set computer instruction set architecture developed by Hitachi. It is implemented by microcontrollers and microprocessors for embedded systems....
  
  
• SPARC
  SPARC
  SPARC is a RISC instruction set architecture developed by Sun Microsystems and introduced in mid-1987....
  
  
  • ERC32
    ERC32
    ERC32 is a radiation-tolerant 32-bit RISC processor developed for space applications. It was developed by Temic . Two versions have been manufactured, the ERC32 Chip Set , and the ERC32 Single Chip . These implementations follows SPARC V7 specifications...
    
    
  • LEON
    LEON
    LEON is a 32-bit CPU microprocessor core, based on the SPARC-V8 RISC architecture and instruction set. It was originally designed by the European Space Research and Technology Centre , part of the European Space Agency , and after that by Gaisler Research. It is described in synthesizable VHDL...
    
    

RTEMS is designed to support various open API standards including POSIX

POSIX

POSIX , an acronym for "Portable Operating System Interface", is a family of standards specified by the IEEE for maintaining compatibility between operating systems...

 and uITRON.