I seem to recall that he talks about step size. The technique you're referring to is called triangulation, where you use sets of inputs/outputs to progressively

I seem to recall that he talks about step size. The technique you're referring to is called triangulation, where you use sets of inputs/outputs to progressively generalize the implementation. It's good to know how to work at this small "step size" for those occasions that you're working on something complex or simply don't have much of an idea about how to implement something. If you're coding a familiar problem then you can increase the "step size" and not take all the baby steps i.e. for the example you mention you would probably just use a single input/output set and code the final implementation immediately. The key is understanding that you can start with a larger "step size" and then backtrack and increase the granularity of your steps if you find things are getting a bit hairy...