Re: Advantages

[Jim Rogers <jimmaureenrogers@worldnet.att.net>]

"Andrew Carroll" <andrew@carroll-tech.net> wrote in 
news:mailman.165.1088318818.391.comp.lang.ada@ada-france.org:

> Have any tests been done to show that Ada tasking features are better
> that other languages' "tasking" features if the model is the same?  If
> so, where are the results?  How much better were the Ada tasking
> features?

Ada concurrency features are generally at a higher abstraction level than
for other languages. The higher abstraction level has many benefits.
The higher abstraction level allows a particular target implementation to
be transparent to the Ada programmer, providing a high level of source
code portability. In languages such as C or C++ you must choose the
appropriate low level threading library, such as pthreads or winthreads.
The Ada concurrency model includes some very sophisticated concepts such
as read/write locks, monitors, condition variables, queued calls 
involving condition variables, programmer-defined queuing policies,
and conditional suspension of calls waiting in a queue (under the
control of the calling task).

All these features can be implemented using the threading facilities
of an underlying OS, or they can be implemented without an OS. The 
difference to the programmer is his choice of a compiler. Some Ada
compilers are specifically designed to produce code for a specific
OS while others are designed to produce code for bare hardware, with
no underlying OS.

>> I'm not saying someone can't do a better job with Ada - just that an
> OS is *really hard* to make stable and secure and it isn't something
> that can be done in a
>> few weekends of coding and hope it will somehow be better.
> What features of Ada help to make an OS stable and secure?  Bounds
> checking?  Typing?  Rendezvous?  Protected Objects?

All of those are tools that help the OS designer. They help because
each resolves several areas of uncertainty in implemented and executing
code.

Jim Rogers