DRYOS

DRYOS is a real-time operating system made by Canon and is used in their latest digital cameras and camcorders.
Since late 2007 DIGIC-based cameras are shipped using DryOS. It replaces VxWorks from Wind River Systems which has been used before on Digic2 (DIGIC II) and some Digic3 (DIGIC III) cameras. DryOS had existed before and was in use in other Canon hardware, such as digital video cameras and high-end webcams. 
DRYOS has a 16 kilobytes kernel module at its core and is currently compatible with more than 10 CPU types. It provides a simulation-based development environment for debugging. Canon also developed a USB- and middleware-compatible device driver for file systems and network devices like video server.
DRYOS aims to be compatible with µITRON 4.0 and with POSIX.
Cameras with DRYOS.
The following cameras are known to run DRYOS: