Day by day technology allows devices to be slimmer, smaller and better for mobile computing by design , so the size of portable computers (both in thickness and weight) is decreasing.
Here, We have mentioned the notebook,laptop and ultrabook technology.


           A notebook is an extremely lightweight personal computer. Notebook computers typically weigh less than six pounds and are small enough to fit easily in a briefcase. Notebook computers use a variety of techniques, known as flat-panel technologies, to produce a lightweight and non-bulky display screen. In terms of computing power, modern notebook computers are nearly equivalent to personal computers. They have the same CPUs, memory capacity and disk drives. However, all this power in a small package is expensive.
               Sometimes notebook formally known as the “small laptop”


                    A laptop is a small, portable computer — small enough that it can sit on your lap. Nowadays, laptop computers are more frequently called notebook computers, though technically laptops are somewhat larger in size than notebooks, in both thickness and weight.
                    The laptop was originally designed to be similar to a desktop but be small and light enough that it could be used while sitting in your lap. 



                   Ultrabook is a specification and brand developed by Intel for a class of high-endsubnotebooks which are designed to feature reduced bulk without compromising performance and battery life. They use low-power Intel Core processors, solid-state drives, and unibody chassis to help meet these criteria.Due to their limited size, they typically omit common laptop features such as optical disc drives and Ethernet ports.
            An Ultrabook needs to measure 18mm (0.71 inches) or less in thickness for systems with displays less than 14 inches and 21mm (0.83 inches) or less displays larger than 14 inches. There is no weight limit for Ultrabooks but most weight between 3 and 4.5 pounds. There are also no restrictions on the size of the display, but the sweet spot seems to be between 13 and 14 inches.