Use the most appropriate type. If you don't know what that is, use `int`. My general rule of thumb is "use unsigned integers when interfacing with hardware, otherwise use int.". Sometimes you need int64_t. You usually don't.
The problem with unsigned integers is that most people, past me included, think that it prevents nonsense negative values. It doesn't. The compiler will quite gladly let you call a `void func(unsigned x)` with -1 and let you have "fun" later debugging why who and how this function got called with an enormous value.
And, of course, that's not the only source of negative numbers that get passed in by mistake. More often it's the result of a subtraction that can "never" be negative.
The problem with unsigned integers is that most people, past me included, think that it prevents nonsense negative values. It doesn't. The compiler will quite gladly let you call a `void func(unsigned x)` with -1 and let you have "fun" later debugging why who and how this function got called with an enormous value.
And, of course, that's not the only source of negative numbers that get passed in by mistake. More often it's the result of a subtraction that can "never" be negative.