Interested to know who 'Hugh B-S' was! Great content again... even *I* could program assembly with such a good environment! Today's MAP files leave a lot to be desired.

My dad worked on the Apollo Guidance Computer design and software for Snoopy et al. He graduated from MIT with a degree in "automatic systems" and worked for Grumman on the LEM and the AGC and guidance system. He also was well versed in inertial navigation systems, radar, radio, computer design and programming and celestial navigation etc. Anyway, he had piles of those program folders that he would sit on his bed and pour over line by line, debugging errors one line at a time. Back then, to debug a program or analyze its performance they would run the program till they got an error, mark the line and then study that line of code to see what was causing the error. Since this was the 60's no one had a computer at home, so you had to debug line by line. And there were so many lines of code that one person couldn't debug the whole thing. So they printed up many copies and gave them to everyone to take home to debug a portion of the program. I know he had at least a half ton of those printouts stacked up floor to ceiling in his bedroom so they must have printed out hundreds of copies. And if they revised the program in anyway then all the previous versions became useless scrap paper. Of course, nowadays they are valuable historical artifacts that show the evolution of the whole programming part of Apollo. But in my day, they were just something that as a teenager I couldn't understand and something my mom complained about having to trip over in her bedroom. And yes I seem to recall there being a lot of strange comments in those printouts. Nasa even had small pins made that showed Snoopy in a space suit and helmet that they gave out to everyone working on the project.

I am an Apollo Engineer who was the Emergency Control Rate Gyro Guy. Mostly flight hardware . A little programming. Linking other programs . I got to send Gyro signals to the Capsule at T minus 2 min30 sec. The highest excitement of my life!!

It's downright criminal that this doesn't have millions of views and likes. Such an important part of computing history is being preserved and studied, here! I truly shudder to think what's going on in my modern laptop as I type this, and if its various codes and chip layouts were to be printed on paper if there is even a warehouse big enough to contain it all. YOU CAN PICK UP AND HOLD the apollo software. That is so amazing. One of the unsung heroes of the apollo program, in my opinion, was the ranging system they used, with the Unified S-band pseudo-random codes and the FANTASTIC precision they achieved in the 60s. If you ever discover information about that system's development, it would definitely be worth pursuing!

As a former IBM Series/1 assembler programmer from the 1980's, this video brought back many fond memories (no pun intended) of reading through big, fan-fold greenbar printer listings. You guys are awesome software archeologists in posession of some of the most significant computer code ever written. This is historic code that directly enabled human footfalls on another world.

Fascinating. I wrote a lot of assembler in 67-76. Talk about cards. We had multiple pallets of cards delivered every other week or so. And green bar paper. I just can't believe that someone held on to this printout (safely no less) for all these years. Good stuff. That young man is on his game.

How they achieved this in the 60s is incomprehensible. It's not like they could just write an EEPROM with their code and test it with a simulation. How they got it this bug free is insane. We talk about cutting edge now, this I feel was pushing it even further. A computer to some people in the 60s would have just sounded like a foreign language. This is such a great channel!

Don Eyles, a name that most people probably do not recognize, is one of the great unsung heroes of the Apollo program. May he live long and prosper.

My first programming experience was RATFOR, then FORTRAN using and IBM at WVU to solve aerospace engineering design, structures and fluids problems in 1968/69. So I recognize the cards, etc. in 1969 I was on my first job and moved from cards to paper tape to analyze flight test data and calibration data using FORTRAN on a HP mini computer. A year later, I designed and coded assembly language programs to simulate surface to air, air to air missiles, and radar/IR hardware and man in the loop testing in real time! This taught me so much that about architecture and computer cpu/gpu operations and algorithm development. I still have boxes of cards, program listings etc to remind me how far we have come in just 50 years.

Fascinating trip back in time, thank you Mike and Marc. That was a good explanation of the layout of an assembler listing too, showing the one-to-one relationship between machine instructions and assembler language statements. Around the same era I was writing air traffic control software in IBM/360 assembler code (BAL) and it all came flooding back to me. I have happy memories of six inch thick assembler listings and boxes of punch cards, just like this. Too much of this history of computing has been lost for ever, so it's wonderful that you are rescuing, restoring and archiving for future generations.

I (and several others) were assigned to "translate" the code in that listing, generate flow diagrams that could be understood by real human beings and teach classes down at the Manned Space Craft Center in Houston. It was a BIG job because the MIT programmers did not always give written comments, to the side of the instruction flow, to help people understand what they were trying to do. Often times they would do a "weird" shifting of "words" in order to interrogate a particular bit (for instance a bit that meant a specific switch was on or off). We had to figure it out, ourselves. It took MONTHS of laboring over those Apollo listings to come up with those flow diagrams.

I cut my teeth programming in hex and assembly - I was 2 years old when this was assembled! I always will be a low level guy! This is one of the most interesting video's I've ever watched. Thank you so much for all your work and dedication to the project.

Assembly code with comments. Amazing.

I build Industrial control systems and I've lost count of the number of times I've written software fixes for bad hardware. Rarely are they as elegant and simple as that fix.

Assembler programmers and real time processing programmers are a very special breed. I spent my computer programming career donig that. Reading the green bar was a treat, especially when tracking down a bit problem on spacecraft. Remember this is an era when bytes and words were it. Computers might be eight or sixteen bit machines. You tended to memorize a lot and work between binary, octal, decimal and hex.

The moon landing is one of the most important technological leaps in the history of mankind. Out of all the billions of humans that ever existed, 99.9999999999...% have never even been outer space, nevermind landing on the moon! This video is a part of that history and hundreds of years in the future (if we are still existing) this video will be a relic to something that was great.

Its so cool to see the exact changes the programmers made to fix 1202. Love your videos, thanks for sharing.

Those who could understand these programs are revered till this day. I could barely understand assembly language, but I still remember carrying the hugh pile of print outs during my programming term assignment.

I really have no clue how Mike is able to store so much knowledge and information in this young brain of his and have it at the ready whenever Marc is asking him any in depth question. I mean, he is answering almost everyone of them off the top of his head. Does he suffer from photographic memory or does he have cybernetic implants already ? It kinda makes my programming job feel like I'm building Lego sets with a 4+ rating by comparison. Unbelievable. I also wonder how many hours and money went into all of this. After all it's "just" a hobby, right ? Anyway, you guys rock so hard, I can't wrap my head around it !

As someone who learnt to code on 6502 back in the day. This has some beautiful features built into it and looks very familiar. Thanks for this series its fantastic.

Mike's depth of knowledge is amazing, same with Ken.

At just about the same time as the MIT programmers were fixing the 1202 bug, I was learning IBM 360 BAL for fun. This video is so cool, and it seems like both just yesterday, and a long time ago.

One of the things I love and appreciate so much about so many CuriousMarc videos is the level of shear information that is there. This video is no let down. I've watched it a few times and there's just so much information and enthusiasm there. This is why I get excited about new videos. Great informative work guys!

Fantastic! Love Mike's enthusiasm for this stuff.

That way they wrote that code is a work of art. The way everything is organized and commented makes simple to follow. Had to make it a hell of a lot easier to troubleshoot and modify. Neat to see how the 1202 fix was done. Great work as usual Marc, Mike, and the rest of the Curious Crew.

I remember my Microprocessor language Professor telling us (in 2001) that Computer Scientists decades ago , in order to save a few bytes of memory space had some Programs rewritten entirely . This was after he had written two versions of one Assembly Language Program with one version of the Program saving a few bytes of space. Memory space was considered very precious .

It’s not about how many bits you’ve got, its about how you use them ;-) Thank you for making these epic videos! Greetings from Belgium

Thank you so much for the job you do. I've spent several hours browsing the PDF you uploaded with the code/documentation. What a massive job it must have been to scan all those pages. I'm very grateful!

I'm in awe of assembly programmers. I learned FORTRAN in the 80s working on VAX/VMS and Modula-2 on Unix mainframes. Primitive compared to today, it was still a far cry from programming in assembly language. I learned some assembly language but never had to actually try to program in it, thankfully! Fascinating video, thank you for sharing!

At 10:59, that feature where the code listing tells you how many times before a label has been used (REF) and the page number (Card Index) of its last occurrence is a "trace" feature. Most assemblers (or post assembler analyzers) have trace features like this, but they are not used much anymore since we all have computers and monitors on our desks that have source code specific editors - like Gnu's Emacs or IDEs like NI's LabWindows/CVI or Microsoft's Visual Studio. Those editors are so comprehensive and quick to browse code, there is little need to print out source listings anymore - not to mention having trace listings in them. I can't remember the last time I printed out a code listing... I think it was the mid 80's.

The enthusiasm you all have for this stuff is infectious. So infectious that ever since I have watched your video on SCMP and AGC, my interest in the core working of these machines has increased!! Although I know only a teeny-tiny bit of AVR assembly, these videos are real gold and should be preserved!!

Man, i never thought i would be watching the *Apollo 12 source code* . THIS, this is really cool content. I actually dont have words to describe this, it's just amazing to see this...

Wow what a fantastic explanation of the way that the code went together thank you.

Thanks for deep diving all things Apollo especially the AGC. This has always fascinated me.

Absolutely fascinating yet again. So much information even in each line.

Version control in the late 1960s! Very cool.

Worked on some mini computers in the 70's and 80's. Looking at that assembly on 'greenbar' paper takes me back. Wasn't the same assembler of course, but yeah, reading those columns with the instruction, reference addresses, comments, and all the rest was an everyday thing back then. And the assembler programs themselves, that kept track of all the 'labels' and references to print out the table at the end was something. We would spend hours flipping between the tables at the end and the listings. And to think, they were doing this decades before the TRS-80 or IBM PC.

A nice piece of real History. Thank you all for showing it to us.

For me, this is by far the most interesting video of the series. I'm a retired electrical engineer and spent a significant portion of my career on real-time software development (please everybody stop using the word "coding" -- it is highly insulting). My intro to computer languages was in high school, where an IBM employed neighbor brought to me an instruction manual IBM used to teach PL/1. I was instantly hooked. But, I never advanced to the point where any of my programs could be submitted for execution. In college, my very first semester (in 1973) included a FORTRAN course, in which we punched cards for batch submission to the Xerox Sigma-6 beast. In between the SPICE runs for circuit courses, I became especially fond of writing ASCII-art programs. Which came to an abrupt halt when the sysop eventually wrote on the top of my card deck something very close to "if you ever submit something like this again, you will be banned from ever using this facility again"

Thank you Marc and Mike. This is a hugely important video, and one that along with the AGC rebuild will be kept for future generations. Anyone starting in systems programming and real time control should watch this and read some of the AGC manuals. There is a lot of knowledge to learn from this. I used to program in assembler in the late 70's and early 80's. I so wish that my assembler had been as helpful as this!

You guys aren't just sharing with the geeks, you're making them. Thanks for sharing! -Jake

The nicest thing about this code is that you only have to change one line at the beginning from "DEST := 'Moon''' to "DEST := 'Mars'" and it would land the astronauts on Mars rather than the Moon.

I love that code isn't some kind of a top secret documentation and we able to dive into and appreciate it.

Really enjoyed this. I did much of my undergrad Computer Science degree with this sort of technology. Brought back memories of performing dry runs to track down bug, using all the features of the listings you discussed. That listing is gold. Comments and code structure give an insight into the mind of the programmer!!

Very interesting. It's crazy to think that such relatively limited technology allowed us to go to the moon, and today we can't even have synchronized, smart traffic lights everywhere in North America. These listings reminded me very much of my early days learning Z80 machine language on my Sinclair ZX81 back in 1982. I was 17. How time flies when you're having fun. Thanks for sharing. BTW, Mike's vast knowledge never ceases to amaze me! Looking closely at some of the listings, the printer had trouble printing clearly the last column which makes it sometimes difficult to distinguish a C from a 0...

No matter how sophisticated we are today, this is still legendary and cool! Thanks for the video, more deep dives like this please!

Mike is the today,s Don.

So much fun to see your work , my grand parents just gave me original new york news prints of the first moon landing in color pictures and all, felt like the first day back then.

Ah, the good old days. Man, I miss Apollo. What a fantastic time. 50 years later we need megabyte executables to print "hello world". That's rather sad. Luckily much has improved, too.

That code deserves to be etched into concrete, not only nerdy computer history but a huge part of the history of humanity.

Many thanks for the detailed video. When I see the straightforward, actually easy to read structure of the programming that was responsible for the successful missions and the rather modest success of various landing missions (moon, mars) today, it makes me think and wonder.

What an incredible, beautiful, irreplaceable artifact.

Thanks for sharing. Can't think of a better way to honour these achievements other than by simply knowing of them. Thanks again!

Thanks for making these videos. Thoroughly enjoyable. I programmed a mainframe on punch cards via a remote job entry station which consisted of card readers and printers, which were connected to an Amdahl IBM/370 clone. I was a high school student taking a programming class at my local state university, in 1982.

I have no clue how I come up here but I loved every minute of it! Very fascinating stuff even if I understood probably a 1/20th of it! ❤

So very interesting! Thank you for spending the time to explain this!

Wow, haven't done any assembler for about 40 years but I can pick my way through some of this. Wow, thanks for the share!

wow ... this is awesome and good work of the programming team. Thank's for share.

A great video explaining how to read the ACG assembler code. Thank you!

This is Great! It's great that you're studying and documenting this. It's also great that you're sharing the examination of this code. I'm an old coder. I learned BAL in college before moving on to Fortran & Cobol, but when I moved into the business world, I had to occasionally write custom routines in assembler, and read core dumps of compiled code. This all brings back a lot of memories. And the coder's comments are exactly the type of stuff we used to lay into our code. Very Cool!!!

Marc, I worked on the Space Shuttle computers for 20 years at IBM and LM and would be very intereted as to whether that computer has a Serial Number on a tag on the side.

"FIX IT IN sOFTWARE!". and still happens even now for us bare metal guys! Love this listing!!

Thank you so much for this ; it's like studying DeVinci drawings but for passionate programmers. Really great.

A fabulous artifact! I wish I could smell it. I can't help but be reminded of the famous picture of Margaret Hamilton standing next to a stack of these printouts as tall as she is.

Great to see this copy of the AGC program, thank you!

Truly amazing stuff. Thanks for sharing !!

It used to be in all the compilers and assemblers I knew about, when you were merging input from tape and punch cards with patches (usually known as patch cards) the asterisk next to the sequence number indicated that this was a patch card. Non-marked input was coming from the master tape. There were other possible flags, like a # sign if you were generating a new merged output tape and also resequencing a range of the input lines. Of course this assembler may have worked differently.

Great work Marc. Thank you for sharing.

Octal I wrote assembler back in 1985. wow brings back memories. I worked on the pre-internet. And Fortran.

The amount of work that went into that code...

Absolutely incredible how these systems were made. Todays stuff is just neat.

Thanks! I really enjoyed this episode.

Respect old developer... ✌️💙

Very interesting. I'm sure glad editing code is a LOT easier than it used to be.

Some years ago, my rodeo group got a guy to program an online contestant registration system in PHP. I designed the interface screens and wrote the requirements for each function. I also specified that all parts of the code was to have function comments embedded within the script. A few years later, the PHP engine on the server was updated and the entire registration system crashed. When I looked at the code, I found there were absolutely no comment markups anywhere in the script. He had not followed PHP standards and just wrote the script so it would work on the PHP version he was writing for, including a bunch of poorly implemented subroutines. Not being able to understand what each section did, required an almost entire recreation of the entire system. I really could have used your friend for that one.

A fantastic insight into NASA documentation. Thank you for your upload.

Incredible video, thanks for sharing!

A piece of history saved, well done all at CuriousMarc

I grew up in the 80s and so I learned a bit of 6502asm for the C64 and a bit of 68K asm for the Amiga. And today I learned about how they programmed the AGC, and how the fixed that infamous 1202 Error. That was extremely interesting, thank you!

Awesome narrative; learned a lot! My grandfather programmed with these systems.

Keep on doing a great job guys!

I really admire your work and your genius. I have used assembly language to program the 6502, the z80, the 6800 family, the 8051 family and some PICs, but that was just a couple of drops compared to the ocean of your work.

it would be fantastic to have a movie made with attention to the things that your group and others have found.

Ken is the funniest, his quips make my day

I would love to have Mike as a friend. I bet he is fascinating to talk to. I thought I was the only person that was this fascinated by software lol.

7:28 In 1973 I dropped two boxes of punch cards and they spread all over the floor. Luckily they were numbered from column 73 onward and there were many larger groups of cards that did not separate. It still took me all day to put the decks back together and my boss was NOT impressed. Unfortunately the company I worked for did not have a Hollerith card sorter which would have made my job so much easier.

Viendolo.... Simplemente Es Espectacular..... muchas gracias....❤

brings back a lot of memories when i was still working in a bank using an IBM mainframe. Compiling source code takes the time of a coffee break, then when its finished there would be an error becoz of a misplaced period. Grrrr

I love the cross-referencing info in the listing. I wish I had known about this when I worked on an assembler and a compiler in the 1970's. They had comprehensive cross-reference listings, but now I wish I could go back and make them even better. And I wish modern compilers told you all of the things they know about your code that you don't.

Long time no see!!!

This feel like alien technology. Simply amazing

Thank you for this its so interesting keep up the good work

When you were talking about the symbol table, you talked about the first page and last page number of the reference of a symbol, but didn't know what the middle number was. If I remember correctly the middle number was the page the symbol was defined on.

I used to read core dumps on IBM mainframes for COBOL programmers as I was one of the only assembler programmers there. I used to diagnose 3,000 page CICS dumps. Then the operations manager decides "it was a waste of paper to print dumps" so instead if paper I would get microfiche on my desk, and I didnt have a microfiche reader!!! I taught at a large college in NY, mainframes and assembly language too. I still prefer assembly language to any other

Brings back fond memories - IBM 360 BAL and PL/1 programs submitted by punch cards and printed on green bar paper on a 1401 with symbol tables in the back. We burned thru a lot of paper back then!

I love the engineers that came up with the 1202 hack. They essentially strangled the CDU with an always-0 command to shut it up.

In the future, humanity leaves Earth, and the robots we left behind build a civilization of their own, worshiping this listing as a holy book. Priest: "...and deliver us from manic RR CDUs, TCF DANZIG."

Loved this, thank you.

At least these guys have the know how to restart the software and enable us to re-land on the Moon again!

Mike seems an amazing guy, I'd like to meet him one day.