Tablet
A tablet, tablet computer or tablet PC is a mobile computing device designed to be held in one or two hands. It is typically the size of a book (7 inches or bigger) and resemble a large smartphone.
Tablet let the users do many of the same things as a traditional computer. They can browse the internet, connect to social network apps, and display HD videos. They excel at application which do not require a large amount of precise user input.
Early tablet devices used light pens or a stylus as their input devices. However, today all tablets use a touchscreen as their primary input devices with the option to connect external devices such as a keyboard. Most tablet only have a few physical buttons, the back power, and volume buttons and everything else can be done using your fingers. Today there are top two operating systems used with tablets. A tablet can have apps installed onto them to perform a function.
The concept of a tablet was first sketched by Alan Kay while at Xerox in 1971 and since then there have been many iterations of tablet devices including PDA’s predecessors to the tablet.
Taken from : http://www.computerhope .com
The size of tablets ……