Writing Software to Last 50 Years
Text files are king! I store every single byte I can in text files. Examples:<p><pre><code>  - Tabular data     : TSV   (almost all Un*x/GNU tools handle this out of the box)
  - Simple "records" : GNU Recutils format (https://www.gnu.org/software/recutils/)
  - Formatted texts  : Markdown, LaTeX, ...
  - ...
</code></pre>
If I need some hierarchical kind of information, I use a folder structure to handle this.<p>I know that not everything can be stored as text. But I try to use open, well documented and future proof formats. Examples:<p><pre><code>  - Images : PNG
  - Music  : FLAC, Ogg, ...
  - If I really need to preserve orignal format/design of a web page: PDF
</code></pre>
Nothing's perfect but stay away from any closed/obscure/proprietary formats.