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.. _introducing_zephyr:
Introducing Zephyr
The Zephyr OS is based on a small-footprint kernel designed for use on
resource-constrained systems: from simple embedded environmental sensors and LED
wearables to sophisticated smart watches and IoT wireless gateways.
The Zephyr kernel supports multiple architectures, including ARM Cortex-M, Intel
x86, ARC, NIOS II, Tensilica Xtensa and RISC V. The full list of supported
boards can be found :ref:`here <boards>`.
Zephyr uses the `Apache 2.0 license`_ (as found in the LICENSE file in the
project's `GitHub repo`_). There are some
imported or reused components of the Zephyr project that use other licensing,
as described in :ref:`Zephyr_Licensing`.
.. _Apache 2.0 license:
.. _GitHub repo:
Distinguishing Features
The Zephyr kernel offers a number of features that distinguish it from other
small-footprint OSes:
#. **Single address-space**. Combines application-specific code
with a custom kernel to create a monolithic image that gets loaded
and executed on a system's hardware. Both the application code and
kernel code execute in a single shared address space.
#. **Highly configurable**. Allows an application to incorporate *only*
the capabilities it needs as it needs them, and to specify their
quantity and size.
#. **Compile-time resource definition**. Allows system resources
to be defined at compile-time, which reduces code size and
increases performance.
#. **Minimal error checking**. Provides minimal runtime error checking
to reduce code size and increase performance. An optional error-checking
infrastructure is provided to assist in debugging during application
#. **Extensive suite of services**. Offers a number of familiar services
for development:
* *Multi-threading Services* for priority-based, non-preemptive and
preemptive threads with optional round robin time-slicing.
* *Interrupt Services* for compile-time registration of interrupt handlers.
* *Memory Allocation Services* for dynamic allocation and freeing of
fixed-size or variable-size memory blocks.
* *Inter-thread Synchronization Services* for binary semaphores,
counting semaphores, and mutex semaphores.
* *Inter-thread Data Passing Services* for basic message queues, enhanced
message queues, and byte streams.
* *Power Management Services* such as tickless idle and an advanced idling
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Fundamental Terms and Concepts
See :ref:`glossary`