REX OS
real-time operating system
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.
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.
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
REX is an RTOS with the following features:
Preemptive multitasking
Task management
Task synchronization
Exclusive lock
Timer
Interrupt management
Uses less than 5K of ROM
REX provides no memory protection features but does have memory management abilities.
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The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Nov 11, 2025. The linked authority identifier is Q7276408. 1 of 1 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank. The first chronological checks are 2007 and 2012.
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This entry incorporates text from “REX OS” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.