Ignoring the software reasons, that are already in the comments. Unhackable software is impossible because direct access is total access. If you make a perfect

Ignoring the software reasons, that are already in the comments. Unhackable software is impossible because direct access is total access. If you make a perfect program running on a perfect OS it still has to operate in the real world. IRL I could change the memory or storage to hack the software via some method other than the OS, bypassing the software entirely.