Zephyr (operating system)

Zephyr is a small real-time operating system for connected, resource-constrained and embedded devices (with an emphasis on microcontrollers) supporting multiple architectures and released under the Apache License 2.0. Beyond its kernel, Zephyr includes all the components and libraries needed to develop a full application such as device drivers, protocol stacks, file systems, and firmware updates.
History.
Zephyr was derived from Virtuoso RTOS for DSPs. In 2001, Wind River Systems acquired Belgian software company Eonic Systems, the developer of Virtuoso. In November 2015, Wind River Systems renamed the operating system to "Rocket", made it open-source and royalty-free. Compared to Wind River's other RTOS, VxWorks, Rocket had a much smaller memory footprint. Rocket could fit into as little as 4 KB of memory, while VxWorks required 200 KB or more.
In February 2016, Linux Foundation launched Zephyr project. Wind River contributed the Rocket kernel to Zephyr. As a result, Rocket became "essentially the commercial version of Zephyr".
Since then, early members and supporters of Zephyr include Intel, NXP Semiconductors, Synopsys, Linaro, Texas Instruments, DeviceTone, Nordic Semiconductor, Oticon, and Bose.
As of August 2020, Zephyr had the largest number of contributors and the largest number of commits compared to other RTOSes (including mbed OS, RT-Thread, NuttX and RIOT).
Features.
Zephyr intends to provide all components needed to develop resource-constrained and embedded or microcontroller-based applications. This includes, but is not limited to:
Configuration and build system.
Zephyr uses Kconfig and device tree as its configuration systems, inherited from the Linux kernel but implemented in Python for portability to non-Unix operating systems. The RTOS build system is based on CMake, which allows Zephyr applications to be built on Linux, macOS, and Microsoft Windows.
Kernel.
The kernel offers several features that distinguish it from other small OSes:
Security.
A group is dedicated to maintaining and improving the security. Also, being owned and supported by a community means the world's open source developers are vetting the code, which significantly increases security.