Integer Overflow Errors
Using an unsigned variable in a computer program can lead to unexpected errors which we call overflow errors.
This is where if we subtract one from the variable when it is 0 it becomes an unexpectedly large number like 4294967295.
This is a problem we can see in Iguana 6.1 which is relatively harmless although alarming looking.
But it’s also the same problem that caused the French Ariane rocket to explode (a $500 million dollar disaster - see https://www.bbc.com/future/article/20150505-the-numbers-that-lead-to-disaster).
Google around and you’ll find all sorts of expensive problems that arise from this issue.
How does it happen? Read about how computers handle subtraction.