From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-0.9 required=5.0 tests=BAYES_00,FORGED_GMAIL_RCVD, FREEMAIL_FROM autolearn=no autolearn_force=no version=3.4.4 X-Google-Thread: 103376,382fcf8feeefdd50 X-Google-Thread: 1014db,382fcf8feeefdd50 X-Google-Attributes: gid103376,gid1014db,domainid0,public,usenet X-Google-Language: ENGLISH,ASCII Path: g2news2.google.com!postnews.google.com!a2g2000prm.googlegroups.com!not-for-mail From: Paul Hsieh Newsgroups: comp.lang.ada,comp.lang.c Subject: Re: computer language used to program Mars Lander Date: Thu, 17 Jul 2008 14:56:22 -0700 (PDT) Organization: http://groups.google.com Message-ID: <13a2f4f0-6ec1-4570-b6bf-1621cfb32db2@a2g2000prm.googlegroups.com> References: <185ee7f9-9d4f-4f49-8dbe-6b623b8a8223@c58g2000hsc.googlegroups.com> <887fc0a7-0a5a-4d2e-a9ea-eb9e32d6a818@m36g2000hse.googlegroups.com> NNTP-Posting-Host: 205.248.102.83 Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Trace: posting.google.com 1216331782 23661 127.0.0.1 (17 Jul 2008 21:56:22 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Thu, 17 Jul 2008 21:56:22 +0000 (UTC) Complaints-To: groups-abuse@google.com Injection-Info: a2g2000prm.googlegroups.com; posting-host=205.248.102.83; posting-account=YIIDlQkAAACt6p2TTji_xJCkqmDPGZsT User-Agent: G2/1.0 X-HTTP-Via: 1.1 SVC-PRXY-06 X-HTTP-UserAgent: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9) Gecko/2008052906 Firefox/3.0,gzip(gfe),gzip(gfe) Xref: g2news2.google.com comp.lang.ada:6928 comp.lang.c:70085 Date: 2008-07-17T14:56:22-07:00 List-Id: On Jul 14, 4:49=A0am, Nick Keighley wrote: > On 14 Jul, 12:18, "jhc0...@gmail.com" wrote: > > > Interesting article I came across on Slashdot: > > >http://developers.slashdot.org/developers/08/07/10/213211.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 technology. Processors are old > (and hence proven) memories are small (less vulnerable to radiation). Indeed. Ada is used by the military, because they have much more sophisticated hardware in tanks and fighter jets. I would expect that perhaps NASA also uses it for the space shuttle. > Remember if there's a bug they can't just upgrade the software. They both can and *DO* do this. They typically use VxWorks as the main operating system, which comes with a fairly powerful command console that makes it practical to actually debug, upload bug fixes and reboot the systems all remotely. > Well they can but it has to be mostly working for the download > to work. Its in the OS they use (and didn't make themselves.) > These are essentially embedded systems and C is still popular > in that world. The small memory footprint and VxWorks environment probably makes C a very attractive language for the NASA guys. If they used Ada, they would be slower, have much larger memory requirements and have a very hard time debugging problems remotely. > I suspect its a damn sight easier to prove C correct than C++. Well by definition, since every C bug can be mapped to a C++ bug (except for certain implicit type conversion failures; but that can be dealt with by requiring that the C code also be compilable with a C++ compiler.) -- Paul Hsieh http://www.pobox.com/~qed/ http://bstring.sf.net/