This might be a good time to point out that the features of a computer regarding this are not doing you any good if you don't know what they are.
A year or so ago I was working with a number of students doing different advanced recreational classes (not technical). On some dives I wold be working with some divers,and on other dives I would be working with others. The divers who were not doing a class with me at the moment would often just do an experience dive at the same time. On one dive, after we ascended, one of the divers with whom I had not been working said his computer (a Suunto) had been acting crazy near the end of the dive. It had given him some strange signal and then started a minute by minute count up. Now it was just saying Er. What was up with that?
I immediately took him down to a platform at 20 feet, and we stayed there for 20 minutes. He seemed fine. I took him back to the surface, explained what had happened, and put him on oxygen for for a while. He was OK.
He had dived with that computer for roughly 140 dives, and he had no idea how it would tell him he needed to do decompression stops