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'[EE:] The Apollo 11 Guidance Computer (AGC)'
2001\02\07@171049 by rich+piclist

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> http://www.perljam.net/misc/apollo11-code.jpg
This is totally cool but NOT Apollo 11: the listing date is Dec 19, 1969,
5 months after the fact.

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2001\02\07@210627 by Olin Lathrop

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> > http://www.perljam.net/misc/apollo11-code.jpg
> This is totally cool but NOT Apollo 11: the listing date is Dec 19, 1969,
> 5 months after the fact.

At least someone understood the value of comments back in 1969.  Maybe
because back then you couldn't get near a computer unless you actuall knew
something about them.  Too bad that 99% of code written more recently is an
undocumented pile of crap.  Now that anyone can get access to a computer and
a high level language compiler, that's exactly what we're getting.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, spam_OUTolinTakeThisOuTspamembedinc.com, http://www.embedinc.com

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2001\02\08@003631 by Robert Rolf

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So it's revision 131. Who's to say that this EXACT page -didn't-
get used in the Apollo 11? Most of the LEM's were pretty much the
same geometry, so I expect that the control interface didn't get
changed between iterations.

rich+.....piclistKILLspamspam@spam@LCLOGIC.COM wrote:
>
> > http://www.perljam.net/misc/apollo11-code.jpg
> This is totally cool but NOT Apollo 11: the listing date is Dec 19, 1969,
> 5 months after the fact.

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2001\02\08@010101 by Bill Westfield

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   At least someone understood the value of comments back in 1969.

Probably required by government specification.


   Too bad that 99% of code written more recently is an
   undocumented pile of crap.

How would you know that?  Today, I'd expect that a good 90% of the code
written is proprietary and not subject to prying eyes.  A lot of what you
see as "open source" or public domain is written by ... beginners.

On the other hand, I WAS duly impressed that you seem to practice what you
preach, with the code you've kindly made available on your web site being
very nicely commented...

BillW

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2001\02\08@010915 by Chris Eddy
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Ok, I am hooked.  Where do I get the rest of the code, including schematics and
spacecraft electronic wiring?  I for one have always wanted to review these
types of designs.  And I have a passion for rocket history.

Chris Eddy~

Robert Rolf wrote:

> So it's revision 131. Who's to say that this EXACT page -didn't-
> get used in the Apollo 11? Most of the LEM's were pretty much the
> same geometry, so I expect that the control interface didn't get
> changed between iterations.
>

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2001\02\08@090545 by Olin Lathrop

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>     Too bad that 99% of code written more recently is an
>     undocumented pile of crap.
>
> How would you know that?  Today, I'd expect that a good 90% of the code
> written is proprietary and not subject to prying eyes.  A lot of what you
> see as "open source" or public domain is written by ... beginners.

OK, I haven't personally inspected 99% of the code out there, but I can say
that the vast majority of the code I do see is very poorly documented.

I'm mostly a consultant, and occasionally I get called in on a project after
someone else started it.  Most of the time the firmware is in such bad shape
and so poorly documented that it is cheaper to do it right from scratch than
to figure out what the original intent was, document it, find and fix the
bugs, and add whatever features are still left to do.  If the original code
had been written the right way, then this probably wouldn't be necessary.

A good example is going on right now.  We were contacted by a company that
has been trying to design a new industrial product.  Part of the overall
product is a mobile unit that includes solenoids, fluid flow meters, a real
time clock, a keypad, an LCD display, several key switches, an RS-232 link,
an optional cell phone interface, an optional flash memory card interface,
and up to three links to RFID tags and the like.  They told us that the
product was "80% done", and want it finished up.  Apparently they contracted
with another company to design much of the product, and this other company
sub-contracted out the software to some guy who just quit to go to a new
job.  The entire source code they gave me that was supposedly 80% done
consisted of 6,400 lines of C intended to run on a single board computer
embedded in the controller.  There are absolutely no header comments giving
an overall description of what any of the functions were intended to do.
There are a few individual comment lines scattered about the code, but there
are also pages of executable code at a time with no comment in sight.  I ran
a pattern search and found that only 14% of all lines contain any type of
comment.  On inspection, I found that many of those are chunks of code that
have been commented out without any explanation.

I had to tell them the unpleasant news that the software at least is 0%
done, not 80%.  They understand intellectually, but emotionally they have a
hard time abandoning something they claim they spent "a small fortune" on.

Since there is no software investment to protect, and the hardware is a long
way from done too, we are proposing a totally different architecture for the
central controller (there are other architectural problems with the design
that I won't get in to).  This will consist of several distributed smaller
$1 to $10 embedded processors instead of a single $350 single board computer
on a separate board controlling everything directly.  I've given them a
rough verbal outline of what we are proposing, but the real presentation is
tomorrow.

I could site a number of other examples where bad professionally written
code has cost people serious money, but this is long enough already.  Trust
me, these problems are real and I've personally seen them a number of times.

> On the other hand, I WAS duly impressed that you seem to practice what you
> preach, with the code you've kindly made available on your web site being
> very nicely commented...

Thanks.  I really do write all my code that way.  I find that writing good
comments as I write the code is sort of a first pass debugger.  I think that
being forced to explain it to someone else makes you think about it in a
different way which can help point out errors or inconsistancies.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, olinspamKILLspamembedinc.com, http://www.embedinc.com

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2001\02\08@093251 by Don Hyde

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I agree that it's an exemplary piece of self-documentation.  Note that the
museum-piece code sample has a page number in the thousands.  Certainly the
people who picked it chose one with enough comments that a non-programmer
would find something to read.

How much do you want to bet that the other thousands of pages are as well
documented?  Hint: I'll take your bet without ever seeing the rest of the
program.

Now, the space program code was better documented than most code.  There
were people who actually got paid to read the code looking for bugs, and
they expected at least a few clues.  I know because as a NASA co-op at the
time I was one of those people.

I worked with an ex-IBM assembly-language programmer at about that time.  At
the time, IBM had a rule something like "2 comments for every 3 lines of
code", and inspectors to enforce the rule.  He used to write poetry down the
comment side of the listing, and it always got approved even though he was
writing stuff that had nothing to do with the program.

I'm sorry to muss your rose-tinted nostalgia glasses, but the 99%
undocumented pile of crap rule is not new.  It's just that nobody chose the
crap to put in a museum display.

You write code differently if you think another human might actually read
it.  It's a fact of life that the vast majority of source code is never read
by any human other than the original author.  Based on my experience, I
suspect that the vast majority of the good reputation of open-source code
stems from the fact that the authors expect someone else to actually read
their code.

I don't know about you, but I don't think I have ever sat back and read
anyone's source code -- either my own or someone else's without spotting a
potential bug or at least a better way of doing something.

> {Original Message removed}

2001\02\08@104759 by dparker

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People on sci.space.history are planning to scan the 1800 page listing
and then put it on the net.  Followup there.  Gary Neff has the listing.

Chris Eddy wrote:
{Quote hidden}

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2001\02\08@111623 by James Korman

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I'd be willing to bet that any randomly selected page of code
out of this listing has comments at the same detail as the
listed page. Those guys were absolutely paranoid about safety!


Don Hyde wrote:
{Quote hidden}

> > {Original Message removed}

2001\02\08@121926 by Bill Westfield

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>    You write code differently if you think another human might actually
>    read it.  It's a fact of life that the vast majority of source code is
>    never read by any human other than the original author.

Heh.

You write code differently if you think someone else might read it.

You write code even more differently if you think someone else might
SCREW IT UP!!!  (now THERE is motivation for documenting your code.)

BillW

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2001\02\08@130253 by Dan Michaels

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Olin Lathrop wrote:
> >
> > At least someone understood the value of comments back in 1969.  Maybe
> > because back then you couldn't get near a computer unless you
> > actuall knew
> > something about them.  Too bad that 99% of code written more
> > recently is an
> > undocumented pile of crap.  Now that anyone can get access to
> > a computer and
> > a high level language compiler, that's exactly what we're getting.
> >


".. Too bad that 99% of code written more recently is an undocumented
pile of crap..."

Is this a fact you know for sure, Olin?? At NASA? Industry in general?
Can we accept your statement as truth or superstition?

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