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This famous photo depicts Margaret Hamilton, leader of the software engineering team for the Apollo Project, next a print out of the code she and her team wrote for the mission. enter image description here

This information is correct according to this Skeptics SE post and links therein. The question I haven't found an answer to is: why would they print the code on paper?

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user2723984
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    It's easier for humans to read if it's on paper. It will probably last longer on paper than if it was on magnetic media. – JRN May 08 '19 at 13:45
  • I see the second point - it was a more reliable storage, I guess to know what happened in case things went wrong? But by the reasoning of the second point why isn't code printed out today? (or is it?) – user2723984 May 08 '19 at 13:57
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    The wikipedia article Computer programming in the punch card era paints a good picture of the state of programming at the time. According to the article, printing program code on the "fan-folded paper" pictured was primarily for the purpose proof reading. Paper was an expensive but screens would have been much more expensive and limited in size. See, for example, The evolution of computer displays. – nwr May 08 '19 at 17:28
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    What @NickR said. If you look at the workspaces from that era, you will not see a monitor on every desk. In fact, the only monitors in the whole building may be one or two small ones in the computer room. (The compluter takes up a whole room.) They could not use them for proof-reading the code. Instead you may see large file cabinets and shelves, containing print-outs such as those in the picture. I experienced working in an office like this in the summer of 1967. – Gerald Edgar May 08 '19 at 21:43
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    Oh, you kids these days! You probably never saved a program on punch-tape either. – Carl Witthoft May 09 '19 at 12:56
  • @CarlWitthoft I concede, I was naïve and blinded by modern technology! It didn't occur to me that screens back in the days weren't really HD – user2723984 May 13 '19 at 13:40

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This is how computer programming was done in those days. There was no such thing as a modern terminal with a screen, and no keyboards.

A programmer would write her code first on paper (handwritten), then a specialist typist will transfer it to punch cards, using some machine, a kind of typewriter. After several rounds of proofreading, the punch cards will be fed to a computer. The output will be printed on a wide paper strip as rows of text and numbers. What you see in this picture is probably the output. This output was called "wide print" (I don't know the exact English term, just translating from the Russian). I performed all this process as a student in the early 1970-s. Except the punch cards: they were produced by a specialist typist. So proofreading process was painful.

Alexandre Eremenko
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    We American students also typed our own punch cards. – Andrew Lazarus May 09 '19 at 00:26
  • Worth mentioning also is the alternative to punched cards used anyhow by IBM by the late 1960s -- punched paper tape, produced by a 'flexowriter' that simultaneously gave a human-readable paper typed version, equivalent to what was on the tape. It would also take a tape and churn out a readable equivalent if wanted. That's what I remember using anyway. – terry-s May 09 '19 at 22:24
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    @terry-s: according to my memories the perforated tape pre-dated punch cards. Punch cards was a more advanced technology, and at the time I was learning programming (early 70s) it was already out of date. – Alexandre Eremenko May 10 '19 at 02:54