The  15.6 inches  Smartphone , that I envisioned , is a machine ( regardless of what Operating System ) which can have the physical appearance of  a  15.6 inches Laptop ,  or it can have the physical appearance of  a   15.6 inches  Tablet , or it can have the physical appearance of a   "Folding Smartphone which can unfold into a 15.6 inches   Tablet" .  Regardless  whether the  15.6 inches  Smartphone  look like a  15.6 inches Laptop , or look like a   15.6 inches  Tablet or it looks like  a   Folding Smartphone(a folding smartphone that can unfold into a   15.6 inches   Tablet) ,  what they have in common is that , they behave like a  Smartphone ( can  make phone calls and reply phone calls , send emails , sms , WhatsApp , WeChat , Snapchat , Facebook, Instagram, TikTok , etc., etc.  ) and they operate like a  Smartphone and  they have a  15.6 inches screen size , so much so that , a  Laptop can be use as  a Smartphone  and  a   Tablet can be use as  a Smartphone   and  a   "Folding Smartphone which can unfold into a 15.6 inches   Tablet"     can also be a  Smartphone .