Most computer makers have conceived their notebooks to work with a keyboard and mouse, and they will also have a touch pad that can be used to substitute for the mouse. Lap top computers or lap tops come in three varieties, and these are based on the size. An extremely small lap top will generally weigh less than 1.7 kilograms, while a lightweight slim version will weigh up to 2.8 kilograms, and a larger size lap top will weigh up to 3.5 kilograms. The idea for the laptop existed prior to the invention of the personal computer, and was originally developed in the 1970’s. The very first laptop was the Osborne 1, which made its first appearance in 1981.