For the former: technically they are about as undefined as they could be on read. On write, it's a different matter (you could decide to resize the array under the hood). Even so, I think arrays with a particular size always were simply an illustration that there is a point where you have to allocate a physical resource to something entirely imaginary and that's where infinite bounds are no longer acceptable. In the 80's that was '256', in the 90's '65535', nowadays it is more like '4G' but no matter how far we advance there are still hard limits. And on the wire it gets even more constrained.
