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Before the new '.docx`, '.xslx', etc. formats, when it was still just .doc, .xsl, etc., the document format was (as I've heard it told) essentially just a memor

Before the new '.docx`, '.xslx', etc. formats, when it was still just .doc, .xsl, etc., the document format was (as I've heard it told) essentially just a memory dump of Word/Excel's state for that document at the time you saved. And since it's easy to imagine that serializing/deserializing such a complex thing might not be always 100% perfectly idempotent, it would indeed happen that just the act of opening a file would change it in some subtle way. That hasn't been the case in a long time, though.

repler 3y ago
the new formats are actually zip archives believe it or not
- delta_p_delta_x 3y ago
  They are ZIP archives... of XML. That's what the 'x' stands for in '.docx', '.xlsx', '.pptx', etc; it is Office Open XML[1]. [1]: https://en.wikipedia.org/wiki/Office_Open_XML#:~:text=Office%20Open%20XML%20(also%20informally,initial%20version%20as%20ECMA%2D376 https://en.wikipedia.org/wiki/Office_Open_XML#:~:text=Office....
esafak 3y ago
They were reportedly written as memory dumps for speed. https://www.joelonsoftware.com/2008/02/19/why-are-the-microsoft-office-file-formats-so-complicated-and-some-workarounds/ https://www.joelonsoftware.com/2008/02/19/why-are-the-micros...
jeffparsons 3y ago
Worse than subtle formatting changes was some kind of corruption that could slowly swallow bits of your document without you noticing. Sometimes going back before the corruption had visible effects was not good enough to stop it from manifesting again. I remember back in school religiously saving new versions of Word documents so that if the newest version went bad I could start a fresh doc, then copy and paste sections from old versions via Notepad to cleanse the corruption. (Direct Word-to-Word could bring it across — I guess that tells us something about how they implemented copy+paste between documents, too!)
reddalo 3y ago
You're right, Office documents were essentialy a memory dump, but only for Office <= 95 if I recall correctly. Starting from Office 97, they switched to an improved .doc, .xsl, etc. file format (even though it was still binary). That's why modern software such as Office itself or LibreOffice call the .doc format "Microsoft Word 97/2003"

repler 3y ago

the new formats are actually zip archives believe it or not

delta_p_delta_x 3y ago
They are ZIP archives... of XML. That's what the 'x' stands for in '.docx', '.xlsx', '.pptx', etc; it is Office Open XML[1]. [1]: https://en.wikipedia.org/wiki/Office_Open_XML#:~:text=Office%20Open%20XML%20(also%20informally,initial%20version%20as%20ECMA%2D376 https://en.wikipedia.org/wiki/Office_Open_XML#:~:text=Office....

esafak 3y ago

They were reportedly written as memory dumps for speed. https://www.joelonsoftware.com/2008/02/19/why-are-the-microsoft-office-file-formats-so-complicated-and-some-workarounds/ https://www.joelonsoftware.com/2008/02/19/why-are-the-micros...

jeffparsons 3y ago

Worse than subtle formatting changes was some kind of corruption that could slowly swallow bits of your document without you noticing. Sometimes going back before the corruption had visible effects was not good enough to stop it from manifesting again. I remember back in school religiously saving new versions of Word documents so that if the newest version went bad I could start a fresh doc, then copy and paste sections from old versions via Notepad to cleanse the corruption. (Direct Word-to-Word could bring it across — I guess that tells us something about how they implemented copy+paste between documents, too!)

reddalo 3y ago

You're right, Office documents were essentialy a memory dump, but only for Office <= 95 if I recall correctly. Starting from Office 97, they switched to an improved .doc, .xsl, etc. file format (even though it was still binary). That's why modern software such as Office itself or LibreOffice call the .doc format "Microsoft Word 97/2003"