As of today , 20^th.August 2021 , we have quite a number of machines with 15.6 inches form factor . Among them are Laptops with 15.6 inches screen size and Tablet with 15.6 inches screen size , and Cellular Tablet which is quite close to 15.6 inches screen size ( APPLE iPAD 12.9 inches with voice calling 1 2 3 4 ) and folding Smartphone which can unfold to a 15.6 inches Tablet . As a result , 15.6 inches is hitting the sweet spot for a Laptop or a Tablet or a Smartphone . Having said that , the convergence between a Laptop and a Tablet and a Smartphone with a 15.6 inches screen size will occur and the final product that I envisioned is call                    “ 15.6 inches   Laptop/Tablet/Smartphone(ALL-in-ONE) “   so much so that I believe ,   15.6 inches is a good form factor ,  to build  a   Laptop/Tablet/Smartphone(ALL-in-ONE) machine regardless whether the    machine  have the physical appearance of a foldable Laptop , or a detachable Laptop or a Tablet or a folding Smartphone ( foldingSmartphone which can unfold to a 15.6 inches Tablet ) .