Re: ada portability

[ryer@inmet.inmet.com]

You can expect to get out as much as you put in.  For example, if you
just declare variables to be of built-in types, then behavior may vary
on machines/compilers with different hardware.  If you declare variables
with range and precision constraints to specify exactly what you need,
then all compilers must give you the same behavior.  If you use compiler
or operating-system unique packages (e.g. DEC's package STARLET), compiler-
unique pragmas, etc., then you will loose portability.  If you use
representation specifications to do bit twiddling, don't count on much
portability.  If you write your program carefully, avoiding machine
dependencies, OS dependencies, and unique compiler features, you should
get excellent portability.  The only problem will be different bugs
in different compilers, and this should not be significant.

Ada *enables* you to build very portable software.  Ada also enables you
to write very low-level, machine dependent software.  Both capabilities
can be neccessary.  If you have to pack some bits into a hardware defined-
message packet, and use the operating system to transmit it over a 1553 bus,
then you need to be able to write non-portable code, and Ada will let you.
There are several guidline documents that will help you write code that
is 100% portable.

Hope that helps

Mike Ryer
Intermetrics