REX OS

REX Operating System
REX Operating System
Developer	Qualcomm
Written in	C
OS family	L4A Pistachio and Iguana embedded operating system
Working state	Discontinued
Source model	Proprietary
Initial release	1999 (1999)
Marketing target	Smartphones
Supported platforms	ARM
Kernel type	Microkernel RTOS
License	Proprietary

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

REX is an RTOS with the following features:

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

References

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

External links

Iguana Archived 2006-04-26 at the Wayback Machine
L4 Based Operating Systems Archived 2018-06-14 at the Wayback Machine
NICTA L4-embedded Kernel Archived 2014-02-27 at the Wayback Machine
Qualcomm Corporate Site

[baidu-1] "REX and Common Software". Retrieved 2025-11-11.

[TJ-2] Edgewall Software. "HTC Vision". Retrieved 2012-03-12.

[nextgen-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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