computer language used to program Mars Lander

[jhc0033]

Interesting article I came across on Slashdot:

http://developers.slashdot.org/devel...0/213211.shtml

They are using C at JPL to program Mars Lander and just about
everything now! Not Ada. Anyone got an explanation? I wonder also, do
they really mean C++ when they say C. In my experience, this is a
frequent, although disagreeable usage.

[jacob navia]

jh*****@gmail.c om wrote:

Interesting article I came across on Slashdot:

http://developers.slashdot.org/devel...0/213211.shtml

They are using C at JPL to program Mars Lander and just about
everything now! Not Ada. Anyone got an explanation? I wonder also, do
they really mean C++ when they say C. In my experience, this is a
frequent, although disagreeable usage.

They do not use even memory allocation. They use a subset of C

I am sure they do not use C++!
--
jacob navia
jacob at jacob point remcomp point fr
logiciels/informatique
http://www.cs.virginia.edu/~lcc-win32

[Nick Keighley]

On 14 Jul, 12:18, "jhc0...@gmail. com" <jhc0...@gmail. comwrote:

Interesting article I came across on Slashdot:

http://developers.slashdot.org/devel...0/213211.shtml

They are using C at JPL to program Mars Lander and just about
everything now! Not Ada. Anyone got an explanation? I wonder also, do
they really mean C++ when they say C. In my experience, this is a
frequent, although disagreeable usage.

contrary to popular expectations space probes are very
conservative in their use of technolgy. Processors are old
(and hence proven) memorys are small (less vulnerable to radiation).

Rememeber if there's a bug they can't just upgrade the software.
Well they can but it has to be mostly working for the download
to work.

These are essetially embedded systems and C is still popular
in that world.

I suspect its a damn sight easier to prove C correct than C++.

a = b + c;

probably does what it says in C (assuming b and c have good values
and it doesn't overflow). In C++ there could be half a dozen
overloaded
operators in there.

--
Nick Keighley

I know not what I appear to the world, but to myself I seem to have
been
only like a boy playing on the sea-shore, and diverting myself in now
and
then finding a smoother pebble or a prettier shell, whilest the great
ocean of truth lay all undiscovered before me.
(Sir Issac Newton)

[george.priv]

On Jul 14, 7:18 am, "jhc0...@gmail. com" <jhc0...@gmail. comwrote:

Interesting article I came across on Slashdot:

http://developers.slashdot.org/devel...0/213211.shtml

They are using C at JPL to program Mars Lander and just about
everything now! Not Ada. Anyone got an explanation? I wonder also, do
they really mean C++ when they say C. In my experience, this is a
frequent, although disagreeable usage.

As pointed out it was subset of C and the size of the software is
relatively small by todays standards if it all fits in 128M (no VM
AFAIK).

The specifics of this project differs from earthly "life safety" type
of applications. If probe software fails, watchdog will reboot it into
the safe mode. There it will sit waiting the instructions/patches from
home. Therefore, a critical part is a bootstrap and communication
module. The rest is allowed to fail and can be fixed.

George

[Keith Thompson]

"jh*****@gmail. com" <jh*****@gmail. comwrites:

Interesting article I came across on Slashdot:

http://developers.slashdot.org/devel...0/213211.shtml

They are using C at JPL to program Mars Lander and just about
everything now! Not Ada. Anyone got an explanation? I wonder also, do
they really mean C++ when they say C. In my experience, this is a
frequent, although disagreeable usage.

This was cross-posted to comp.lang.ada and comp.lang.c. I suggest we
all refuse to take the bait and *not* start a cross-language flame
war.

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"

[Maciej Sobczak]

On 14 Lip, 13:21, jacob navia <ja...@nospam.c omwrote:

They do not use even memory allocation. They use a subset of C

I am sure they do not use C++!

Why? I would expect some parts of C++ being used, no matter how much
constrained is the target environment.
In particular, C++ has better and more expressive type system,
destructors that can ensure proper execution of "exit" actions, better
support for encapsulation, etc. All these are real advantages as far
as safe and secure code is concerned and none of these require
additional run-time resources.

For example, would you like to have custom integer types with range
checking in this critical software? (Expected answer on this group is
"yes".) This is trivial in C++ and almost impossible in C. This alone
is already a reason to prefer C++ over C for such systems.

Now, why there is no Ada on Mars is another story - but don't worry
about what Martians will think: they will not see the source code
anyway. ;-)

--
Maciej Sobczak * www.msobczak.com * www.inspirel.com

[CBFalconer]

Keith Thompson wrote:

"jh*****@gmail. com" <jh*****@gmail. comwrites:

>Interesting article I came across on Slashdot:

http://developers.slashdot.org/devel...0/213211.shtml

They are using C at JPL to program Mars Lander and just about
everything now! Not Ada. Anyone got an explanation? I wonder
also, do they really mean C++ when they say C. In my experience,
this is a frequent, although disagreeable usage.

This was cross-posted to comp.lang.ada and comp.lang.c. I
suggest we all refuse to take the bait and *not* start a
cross-language flame war.

It has nothing to do with wars. It is simply an illustration that
proves that it is _possible_ to generate accurate code with C. It
is also possible with assembly language. However, doing so
requires good programmers with plenty of experience. You can get
equal quality from poorer programmers with less experience by using
Ada. I leave it to you what you will get with experienced good
programmers and Ada.

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home .att.net>
Try the download section.

[Maciej Sobczak]

On 14 Lip, 13:49, Nick Keighley <nick_keighley_ nos...@hotmail. com>
wrote:

I suspect its a damn sight easier to prove C correct than C++.

* * a = b + c;

probably does what it says in C (assuming b and c have good values
and it doesn't overflow). In C++ there could be half a dozen
overloaded
operators in there.

Your reasoning is completely broken.
Let's try this one:

I suspect its a damn sight easier to prove C correct than Ada.

a = b + c;

probably does what it says in C. In Ada (substitute := for = ) there
could be half a dozen overloaded operators in there (and some
controlled operations as well).

Do you think that there are some monkeys in the project that randomly
overload operators? If yes, then Ada is equally vulnerable.

Another point: the operator + in C *is* overloaded and not only its
meaning, but also the generated object code differs depending on the
types of a and b. Yes, this is what overloading is all about and yes,
you can have serious errors in C because of that, especially when
combined with implicit conversions. What C++ or Ada can offer in this
area is at least to get rid of those implicit conversions. This is a
huge gain for proving correctness of the code.

--
Maciej Sobczak * www.msobczak.com * www.inspirel.com

[Stephen Leake]

"jh*****@gmail. com" <jh*****@gmail. comwrites:

Interesting article I came across on Slashdot:

http://developers.slashdot.org/devel...0/213211.shtml

They are using C at JPL to program Mars Lander and just about
everything now! Not Ada. Anyone got an explanation?

They are comfortable with their current tools, and simply refuse to
consider others.

I run into that attitude all the time. Even when they are considering
adding tools like static analyzers, they won't consider changing
languages. It's extremely frustrating!

In the short run, sticking with what you know is safe. In the long
run, it is a significant loss of productivity. JPL and many, many
other places are sticking with the safe route.

--
-- Stephe

[jhc0033]

On Jul 14, 4:49 am, Nick Keighley <nick_keighley_ nos...@hotmail. com>
wrote:

contrary to popular expectations space probes are very
conservative in their use of technolgy.

I disagree. Actually, the space industry will try anything and stick
with it until stuff explodes (Ariane rocket) or crashes into the wrong
celestial body because of faulty software. They did use Ada widely
before, and they even programmed some of their probes in Lisp. Seems
like C is the new fad there. Wait until they get bitten by macros and
dangling pointers.