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The switch to digital documents entails two separate problems: obsolescent media and unreadable software formats.
The obsolescent media problem is hardware-related. Digital storage media are much more fragile than nondigital ones: parchment lasts millennia when handled well, hard drives just a few years. Furthermore, digital media go out of date as new and better ones are invented—for instance, lots of people stored documents on floppy disks in the 1980s and 1990s, but hardly any computer systems can be found now with floppy disk drives.