Re: what is RTOS??
A system in which the timely completion of tasks is important. A delayed response is as good as a bad response !
Real-time systems satisfy a completely different set of requirements. A real-time system must never be overloaded. As soon as no more processing power is available, real-time response cannot be sustained.
For example, a situation with real-time requirements might be: a meter generates data every second. The data must be collected, processed, and stored by the computer. If processing a data record requires more than a second on the target computer, the system is overloaded and real-time response cannot be sustained.
Added after 4 minutes:
Sorry for break due to some proxy problem:
Types of Real-time systems : Hard & soft
Hard real-time systems : Are systems in which system reponse time is very critical. Even a small delay in the response time can be fatal or destructive
e.g. : ABS system in vehicles, Flight controller systems, Heart pacemaker
Soft real-time systems : Are systems in which task response, if delayed, is tolerable within a certain limit.
E.g. : Engine control units in vehicles,
So, with so many off-the-shelf RTOS available, which one & how should you choose one ( or, on second thoughts, make one of your own ? ) ?
RTOS, typically, are an expensive lot & cost anything between USD 10 K upto USD 50 K ( runtime royalties not included ! What's that ?? ). Therefore, choosing the right one is important
A low budget RTOS might not burn your pocket, but will come with only a basic scheduler & few other system calls. Some of these also include the source code.
For e.g. Accelerated Technology's Nucleus, kadak's AMX etc.
The fully blown ( & the expensive ones ) typically include a lot of useful functionality beyond just the scheduler. They also assure you of a better real-time performance.
The higher price often includes free technical support, training & a set of integrated development tools. E.g. VxWorks by Eindriver Systems, Integrated Systems pSOS, Microtec's VRTX etc.