Overview

[Wikipedia], an embedded system is a special-purpose computer system designed to perform one or a few dedicated functions, sometimes with real-time computing constraints. It is usually embedded as part of a complete device including hardware and mechanical parts. In contrast, a general-purpose computer, such as a personal computer, can do many different tasks depending on programming. Embedded systems have become very important today as they control many of the common devices we use.

Today, the boundaries between the general purpose PCs, the servers and the embedded systems are more blurred. These computers are sharing same platforms, same peripherals. For example, an x86/Mac PC can be used as a server, an x86/PowerPC CPU can be used in an embedded system like portable navigation device (PND). On the other way, the popular embedded processor StrongARM was a powerful desktop PC processor for the DEC workstation, and the embedded systems often also act servers, like NAS (Network Attached Storage). As same as the hardware suppliers, the OS suppliers port their products into the desktop PCs, servers and embedded systems.

Nothing cuts to the heart of a development project like the choice of OS. Whether it's a tiny scheduler or kernel, an open-source distribution, a tightly wound real-time operating system, a fully featured commercial RTOS, or no OS at all, it drives all downstream software decisions and many hardware decisions as well.

A survey shows us what's important to those who get a say in the choice of OS. The criteria are:

1. Real-time performance
2. Processor compatibility
3. Software tools
4. No royalties
5. Price
6. Memory footprint
7. Simplicity
8. Middelware
9. Compatibility
10. Services & Features
11. Open-source
12. Familiarity
13. Hardware suppport
14. Customization
15. Supplier's reputation
16. Support
17. Popularity
18. Other products

Reference

The resource of OS for embedded systems.

A market research report for embedded OSes

Wikipedia resources of OS for embedded systems

Read also:
http://dev.emcelettronica.com/embedded-os-non-rtos-and-rtos
http://dev.emcelettronica.com/embedded-os-multi-core-os
http://dev.emcelettronica.com/embedded-os-resources-copyright-and-legal-...