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REX OS

From Wikipedia, the free encyclopedia
REX Operating System
DeveloperQualcomm
Written inC[1]
OS familyL4A Pistachio and Iguana embedded operating system
Working stateDiscontinued
Source modelProprietary
Initial release1999; 27 years ago (1999)[1]
Marketing targetSmartphones
Supported platformsARM
Kernel typeMicrokernel RTOS
LicenseProprietary

The REX Operating System (Real-time Executive Operating System) is a real-time operating system (RTOS) developed by Qualcomm for the ARM processor based mobile phone Dual-Mode Subscriber Station (DMSS) or Advanced Mode Subscriber Software (AMSS) development. As of 2007, most Korean cell phones ran on REX.

REX is a combination of two operating systems: L4Ka::Pistachio embedded microkernel and Iguana, with extensive modifications and extensions by Qualcomm and HTC.[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 software and requires a proprietary software license from Qualcomm for use.[3]

It seems not 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.

Features

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REX is an RTOS with the following features:

REX provides no memory protection features but does have memory management abilities.

References

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  1. 1 2 3 "REX and Common Software". Retrieved 2025-11-11.
  2. Edgewall Software. "HTC Vision". Retrieved 2012-03-12.
  3. Asif, Saad Zaman (2011-01-11). Next Generation Mobile Communications Ecosystem: Technology Management for Mobile Communications. John Wiley and Sons. p. 299.
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