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REX Operating System
OS familyEmbedded operating system
Initial release1999[1]
Marketing targetSmartphones
Kernel typeMicrokernel based on L4A Pistachio and Iguana

The REX Operating System (Real-Time Executive Operating System) is an RTOS developed by Qualcomm for the ARM-based mobile phone Dual-Mode Subscriber Station (DMSS) or Advanced Mode Subscriber Software (AMSS) development. As of 2007 most Korean cell phones run on REX.

REX is an L4A Pistachio embedded micro-kernel and Iguana operating system combination and has extensive Qualcomm and HTC modifications and extensions.[2]

Originally developed for the Intel 80186 it was then ported to ARM and x86 architectures are no longer supported. REX is not POSIX compliant or open source and requires a license from Qualcomm for use.[3]

It does not seem to be actively developed or marketed as of 2012 but is used in currently or recently sold low end cell phones, typically for use by pay-as-you-go customers, like the Samsung SPH-M300.


REX is a Real-time operating system with the following features:

REX does not provide any memory protection features but does have memory management capabilities.


  1. ^ a b Staff. "REX and Common Software". Retrieved 2012-03-10.
  2. ^ Edgewall Software. "HTC Vision". Retrieved 2012-03-12.
  3. ^ Saad Zaman Asif. Next Generation Mobile Communications Ecosystem: Technology Management for Mobile Communications. John Wiley and Sons, 2011-01-11, p. 299.

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