Post by thread:[EE:] The Apollo 11 Guidance Computer (AGC)

> 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. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

> > 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_OUTolinTakeThisOuTembedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

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+.....piclistKILLspam@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. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

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 -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

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. > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

> 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, olinKILLspamembedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

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}

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}> > 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. > > > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. -- Donald C. Parker, Keystone Applications, Brooklyn, WI Phone: 608-835-9264 Primary Inet: .....dparkerKILLspam.....execpc.com Secondary: EraseMEparkerspam_OUTTakeThisOuTacm.org WWW: http://www.execpc.com/~dparker An alarming new study shows that U.S. students are doing worse than ever on standardized math tests because many of them can no longer figure out how to turn on their calculators. Dave Barry, 1993 in Review -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

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}> > 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}

> 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 -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

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? -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.