# How can I ensure that old documents will compile in the future?

I was looking through some old files recently, and it occurred to me that they might be obsolete in the future. Are there any steps that I should take for "archiving" my documents so that they will compile properly on later versions of LaTeX? I once went to a seminar where it was indicated that the .dvi file can be converted back into a plain TeX file, so would it be the best "archival" document?

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Only use plain `tex`? There is supposedly a reason the version number is converging to Pi... :p –  Sharpie Oct 26 '10 at 0:04
@Sharpie: you forgot "... and only use Computer Modern fonts." –  Charles Stewart Oct 26 '10 at 12:05

The `bundledoc` package gives you a way to zip up all the classes, packages and files that are needed to process your document. If you save this archive then this should be sufficient information to process your document in the future.

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Would old classes and packages be compatible with new versions of LaTeX? I would hope so, but I think that it becomes quite cumbersome to maintain compatibility over such a long span. –  Johnson-Leung Oct 26 '10 at 4:23
Even if latex3 ever comes out, I can't see latex2e going away for a very long time. It has hardly changed since 1994 and too many people depend on its stability. –  Lev Bishop Oct 26 '10 at 4:58
In particular, academic journals and publishers will not be keen on investing the resources needed to convert their class files over to make use of Latex3's strengths. –  Charles Stewart Oct 26 '10 at 13:01

If you can save old TeX trees/installations, then you can do that. They tend do take less and less space over time (as disk size increases). Then you can be sure of 100% compatibility.

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Another package which helps is snapshot. It provides a list of all packages that are used by a document, so you can package with (or arrange to keep in your system the right versions of) everything needed to reproduce your archived document.

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Plain Tex source files that use only Computer Modern fonts, per Sharpie's comment, is the most change-resistant Tex format there is.

I once went to a seminar where it was indicated that the .dvi file can be converted back into a plain TeX file

It can be true, if specials are inserted into the DVI, but by default it is not true, and the meaning of inserted specials is left wide open to interpretation: are they meta-data or Postscript? Special-less DVI is a well-documented, equally change-resistant format, but a problem here is that the DVI file stores information about fonts in a way that is open to interpretation. If you only use Computer Modern fonts, this won't be a problem.