Oh my. We are quite a history-less field, aren't we, in computing? I programmed an OPAC system in the 1980s and we were not the first by any means. What you mean by "bibliographic information" is called metadata. There were many different systems (MARC - Machine-readable Catalogue) around. We argued about things like having multiple of the same tag for all the different authors or having different tags so we could model the order of the authors. In Germany the art of cataloging literature goes back more than a century. There is the RAK (Regeln für die alphabetische Katalogisierung, https://de.wikipedia.org/wiki/Regeln_f%C3%BCr_die_alphabetische_Katalogisierung) that was put forth in the 70s to get away from that horrible Preußischen Instruktion used since 1899 or so.

We used index cards for keeping track of references in our own publications. We used pen and pencil to write on the cards, or even typed them up on a typewriter. The cards were very easy to sort (and re-sort), so the last thing you did was type up the reference list. Or you used BibTeX, if you had access to a machine that could run it. There were lots of computers before the IBM PC, they just weren't personal computers. If you didn't have access to a computer, you used a typewriter and lots of Tipp-Ex. Or you ended up retyping every page when the number of errors got to be too many.

I suggest reading up on the history of library catalogues (VOX will point you to a book in English on the subject https://www.vox.com/culture/2017/4/21/15357984/card-catalog-library-of-congress-history) and then about OPACS (https://www.tandfonline.com/doi/abs/10.1179/174581607x254802) if you want to look a bit deeper into the history. But you need to go back more than 25 years.

Oh my. We are quite a history-less field, aren't we, in computing? I programmed an OPAC system in the 1980s and we were not the first by any means. What you mean by "bibliographic information" is called metadata. There were many different systems (MARC - Machine-readable Catalogue) around. We argued about things like having multiple of the same tag for all the different authors or having different tags so we could model the order of the authors. In Germany the art of cataloging literature goes back more than a century. There is the Regeln für die alphabetische Katalogisierung (RAK) that was put forth in the 70s to get away from that horrible Preußischen Instruktion used since 1899 or so.

We used index cards for keeping track of references in our own publications. We used pen and pencil to write on the cards, or even typed them up on a typewriter. The cards were very easy to sort (and re-sort), so the last thing you did was type up the reference list. Or you used BibTeX, if you had access to a machine that could run it. There were lots of computers before the IBM PC, they just weren't personal computers. If you didn't have access to a computer, you used a typewriter and lots of Tipp-Ex. Or you ended up retyping every page when the number of errors got to be too many.

I suggest reading up on the history of library catalogues (VOX will point you to a book in English on the subject) and then about OPACS if you want to look a bit deeper into the history. But you need to go back more than 25 years.