Microsoft open-sources "the earliest DOS source code discovered to date"
https://arstechnica.com/gadgets/2026/04/microsoft-open-sources-the-earliest-dos-source-code-discovered-to-date/> This source code is old enough that it hadn’t been stored digitally. “A dedicated team of historians and preservationists led by Yufeng Gao and Rich Cini,” calling itself the “DOS Disassembly Group,” painstakingly transcribed and scanned in code from paper printouts provided by Paterson. This process was made even more difficult because modern OCR software struggled with the quality of the decades-old printout.
I've been able to OCR letter-quality printer output to 97% (mostly Os and Xs problems).
But it seems that machine-learning text-recognition is also now biased to reject computer code because it doesn't look like human language.
> With less-than-satisfactory OCR output, I resorted to a process I used many years ago when converting scans made of old Commodore ROM dumps printed on a Commodore 1515 dot-matrix printer. The process relies on the ASCII OCR output having the same repetitive errors. "B" and "8", "S" and "5" are good examples, as are "l" and "1", and "O" and "0". There are many other similar single-character errors and, when working with x86 code, there are similar errors with instructions like "MOV". This process naturally works better if the output file is monolithic rather than single-page OCR conversions because you can do substitutions across the entire converted printout and not 75 separate files.
> The next formatting hassle was the spacing. This required repetitive substitutions of a descending numbers of spaces to tabs (i.e., replace 8 spaces with a tab, 7, 6, etc.). Then if you want to return it to fixed spaces (which is likely how the original printer printed it -- spaces and not vertical tabs), you can. For pure re-creation work, spaces produce absolute column formatting while tabs can move around depending on the program displaying the file.
> Once you run thought the 15 or so common global substitutions and tab conversion, it's a lot easier to work with the file to fix formatting and perform other cleanup. This is then followed by a line-by-line comparison against the original printouts. Overall I'd say the conversion output quality with this method is very good.