What's the difference between 復帰, 復元 and 復旧

Question

What's the difference between 復帰{ふっき}, 復元{ふくげん} and 復旧{ふっきゅう}?

The both seem to mean restore. (I generally use these words in a computer context as in restoring files or settings.

Related: Difference between 回復, 修復, 復旧 and 復興

Answer 1

復帰 (intransitive)

It originally means "back to original location/position", then figuratively refers to "back to work". This word doesn't imply at all the subject was once out of order: you put your PC in sleep mode, then press the power button, the machine will 復帰する.

復元 (transitive or intransitive)

This word put stress on "to reproduce the original shape". It may or may not indicate it was malfunctioning before you 復元, but if you do 復元, it must look like what it had been like. The "system restore" of Windows is translated as システムの復元.

復旧 (transitive or intransitive)

It means "regain original function, which was disrupted by an unexpected incident". This one explicitly tells that it won't work if you don't 復旧. It focuses on function, so if you データを復旧する, the data should be as it was, but if パソコンを復旧する you're not guaranteed that data stored in your PC was saved too.