Azure RTOS ThreadX is a highly deterministic, embedded real-time operating system (RTOS) programmed mostly in the language C. Overview ThreadX was originally developed and marketed by Express Logic of San Diego, California, United States. The author of ThreadX (and the original author of the Nucleus RTOS in 1990) is William Lamie, who was also President and CEO of Express Logic. Express Logic was purchased for an undisclosed sum by Microsoft on April 18, 2019. The name ThreadX is derived from the threads that are used as the executable elements, and the letter X represents context switching, i.e., it switches threads. ThreadX provides priority-based, preemptive scheduling, fast interrupt response, memory management, interthread communication, mutual exclusion, event notification, and thread synchronization features. Major distinguishing technology characteristics of ThreadX include preemption-threshold, priority inheritance, efficient timer management, fast software timers, picokernel design, event-chaining, and small size: minimal size on an ARM architecture processor is about 2 KB. ThreadX supports multi-core processor environments via either asymmetric multiprocessing (AMP) or symmetric multiprocessing (SMP). Application thread isolation with memory management unit (MMU) or memory protection unit (MPU) memory protection is available with ThreadX Modules. ThreadX has extensive safety certifications from Technischer Überwachungsverein (TÜV, English: Technical Inspection Association) and UL (formerly Underwriters Laboratories) and is Motor Industry Software Reliability Association MISRA C compliant. ThreadX is the foundation of Express Logic's X-Ware Internet of things (IoT) platform, which also includes embedded file system support (FileX), embedded UI support (GUIX), embedded Internet protocol suite (TCP/IP) and cloud connectivity (NetX/NetX Duo), and Universal Serial Bus (USB) support (USBX). ThreadX has won high appraisal from developers and is a very popular RTOS. , according to marketing research firm VDC Research, the ThreadX RTOS has become one of the most popular RTOSes in the world, having been deployed in over 6.2 billion devices, including consumer electronics, medical devices, data networking applications, and SoCs. ThreadX is distributed using a marketing model in which source code is provided and licenses are royalty-free. Supported platforms Analog Devices Blackfin CM4xx Precision Microcontrollers SHARC ULP Microcontrollers Andes RISC-V ARM ARM7 ARM9 ARM Cortex-A ARM Cortex-R ARM Cortex-M ARM Cortex-A 64-bit ARMv8M TrustZone Cadence Xtensa CEVA TeakLite-III eSi-RISC eSi-16x0 eSi-32x0 Infineon XMC1000 XMC4000 Intel Nios II Cyclone Arria 10 x86 Microchip AVR32 PIC24 dsPIC33 PIC32 SAM C-V SAM7 SAM9 SAMA5 MIPS MIPS32 4Kx MIPS32 14Kx MIPS32 24Kx MIPS32 34Kx MIPS32 74Kx MIPS32 1004Kx interAptiv microAptiv proAptiv M-Class NXP ColdFire+/ColdFire