How do they upgrade a computer, that has been calculating something for decades?

Question

If a computer has been for example serching for a really big prime number for decades, how do they upgrade it. Do they stop the calculation or what?

In: Technology

Answer 1

If you have anything that runs for at least days, you want to design your program to have “saves” or checkpoints, etc.

For an eli5 example, let’s say you are searching for really big prime via brute force, and sequentially. You could simply memorize the last number you check. And then continue the search from there.