"Is Windows XP Embedded a real-time OS?
Windows XP Embedded satisfies the vast majority of performance requirements. However, if you require a more powerful real-time support for your Windows XP Embedded OS, you can utilize one of the real-time extensions that are available through third-party vendors."
There are apparently third-party real-time extensions available, but if that counts then the existence of CONFIG_PREEMPT_RT makes Linux a RTOS and I think that'd be a pretty silly claim too.
https://msdn.microsoft.com/en-us/library/ms838350(v=winembed...
"Is Windows XP Embedded a real-time OS? Windows XP Embedded satisfies the vast majority of performance requirements. However, if you require a more powerful real-time support for your Windows XP Embedded OS, you can utilize one of the real-time extensions that are available through third-party vendors."
There are apparently third-party real-time extensions available, but if that counts then the existence of CONFIG_PREEMPT_RT makes Linux a RTOS and I think that'd be a pretty silly claim too.