In a time of change, we often do not notice that Δ = ∫δ. Here I am thinking of network bandwidth, and my personal experience of it over a 46 year period. I first encountered bandwidth in 1967 (although it was not called that then). I was writing Algol code to compute the value of π, using paper tape to send the code to the computer. Unfortunately, the paper tape punch was about 10 km from that computer.