The REX Operating System (Real-time Executive Operating System) is a

real-time operating system A real-time operating system (RTOS) is an operating system (OS) for real-time computing applications that processes data and events that have critically defined time constraints. A RTOS is distinct from a time-sharing operating system, such as Unix ...

(RTOS) developed by

Qualcomm Qualcomm Incorporated () is an American multinational corporation headquartered in San Diego, California, and Delaware General Corporation Law, incorporated in Delaware. It creates semiconductors, software and services related to wireless techn ...

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 system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

s: '' L4Ka::Pistachio'' embedded

microkernel In computer science, a microkernel (often abbreviated as μ-kernel) is the near-minimum amount of software that can provide the mechanisms needed to implement an operating system (OS). These mechanisms include low-level address space management, ...

and ''

Iguana ''Iguana'' (, ) is a genus of herbivorous lizards that are native to tropical areas of Mexico, Central America, South America, and the Caribbean. The genus was first described by Austrian naturalist Josephus Nicolaus Laurenti, J.N. Laurenti in ...

'', with extensive modifications and extensions by Qualcomm and

HTC HTC Corporation ( zh, t=宏達國際電子股份有限公司, p=Hóngdá Guójì Diànzǐ Gǔfèn Yǒuxiàn Gōngsī, first=t), or High Tech Computer Corporation (abbreviated and trading as HTC), is a Taiwanese consumer electronics corporatio ...

. Originally developed for the

Intel 80186 The Intel 80186, also known as the iAPX 186, or just 186, is a microprocessor and microcontroller introduced in 1982. It was based on the Intel 8086 and, like it, had a 16-bit external Bus (computing)#Address bus, data bus multiplexed with a 20 ...

, it was then ported to ARM, and

x86 x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel, based on the 8086 microprocessor and its 8-bit-external-bus variant, the 8088. Th ...

architectures are no longer supported. REX is not

POSIX The Portable Operating System Interface (POSIX; ) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines application programming interfaces (APIs), along with comm ...

compliant or

open-source software Open-source software (OSS) is Software, computer software that is released under a Open-source license, license in which the copyright holder grants users the rights to use, study, change, and Software distribution, distribute the software an ...

and requires a proprietary

software license A software license is a legal instrument governing the use or redistribution of software. Since the 1970s, software copyright has been recognized in the United States. Despite the copyright being recognized, most companies prefer to sell lic ...

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 management is the process of overseeing a task through its lifecycle. It involves planning, testing, tracking, and reporting. Task management can help individuals achieve goals or enable groups of individuals to collaborate and share know ...

* Task synchronization * Exclusive lock *

Timer A timer or countdown timer is a type of clock that starts from a specified time duration and stops upon reaching 00:00. It can also usually be stopped manually before the whole duration has elapsed. An example of a simple timer is an hourglass ...

* Interrupt management * Uses less than 5K of ROM REX provides no

memory protection Memory protection is a way to control memory access rights on a computer, and is a part of most modern instruction set architectures and operating systems. The main purpose of memory protection is to prevent a process from accessing memory that h ...

features but does have

memory management Memory management (also dynamic memory management, dynamic storage allocation, or dynamic memory allocation) is a form of Resource management (computing), resource management applied to computer memory. The essential requirement of memory manag ...

abilities.

References

External links

Iguana

L4 Based Operating Systems

NICTA L4-embedded Kernel

Qualcomm Corporate Site
{{Mobile-software-stub Qualcomm software Smartphone operating systems Real-time operating systems Embedded operating systems Microkernel-based operating systems Mobile operating systems ARM operating systems Microkernels