This *will* just sit and sort numbers over and over again.
I call it 'fishtank' software, because it serves the same purpose as a fish tank (to be interesting but not distracting, i.e. something to get lost in.) Other than that, there is no connection to fish or aquariums.
A distinguishing feature of fishtank software is that it highlights something computers are good at doing. Real fish tanks feature fish which do what they do best: swim. Many fish tanks are also mesmerizing and relaxing. So, fishtank software, which features computers, should do something that a computer does best. I picked sorting numbers, but I tried to make this, like fish tanks, mesmerizing and relaxing as well.
And it will sort and sort and sort.
The sorting algorithm is QuickSort. It's actually really hard to make code that will allow for the sorting algorithm to show intermediate steps. I pretty much ended up making my own emulator which would allow me to control when certain parts of the code were run. What a pain!
Oh yeah, and it also tells the time :)
This is only conceptual. Any real fishtank software would be made with C++ or something, and would make relaxing but unobtrusive sounds as well. Also, there would be more functionality than sorting random numbers. I was thinking of something along the lines of sorting the first 200 results for a random google search.