are most RTOS message-based operating systems?

> or you can consider it the senders role to make a copy to send if it
> needs to maintain an un modified version of the message.

In the case of DPS, it is indeed the sender which does the copying,
the copying code being part of the recipient PSCT, though. IOW, the
sender does a system call which will transfer the message, and the
system takes care of calling the respective code in the recipients
program module.
 Typically, I have two files I link for such purposes, std and qstd,
the latter does queue the incoming signals while the former does
not (it will time out if the recipient task has not processed the
last incoming message for some time; well, so will the qstd as
well, but after the queue has been filled up :-).
 But like I said earlier, this is only one way I use for intertask
communication in DPS. I also do a lot of "object specific" exchanges,
which are mostly using commonly accessed memory pieces
with atomic locks.

Dimiter

------------------------------------------------------
Dimiter Popoff               Transgalactic Instruments

http://www.tgi-sci.com
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jacko wrote:
> Didi wrote:
> > > ....are kept in a Nucleus which use
> > > regular calling mechanisms and copyless message passing.
> >
> > Actually you do need both "copyless" and "copied" message passing.
> > The former obviously saves overhead, the latter comes handy when
> > the mesage is passed by a task which will get killed possibly prior
> > to its message has been processed by the recipient and (the message)
> > resides in memory which will be deallocated when the task is killed.
> >
> > Dimiter
> >
>
> or you can consider it the senders role to make a copy to send if it
> needs to maintain an un modified version of the message.

John wrote:
> Are most modern RTOS message-based operating systems? For example,
> VxWorks, or embedded linux OS? I try to understand how tasks
> communicate with each other? My understanding is that tasks can
> communicate via messages, or mails? Any other approaches?
> 
> please advice. thanks...

Most modern micro kernel based operating systems are message passing based.

VxWorks and Linux are not micro kernel based ...Minix 3.0 and QNX are.

--Armin