How do notebook computers work?

While the terms laptop and notebook are often used interchangeably, "laptop" is the older term, introduced in 1983 with the Gavilan SC. "Notebook computer" is a later coinage, which was used to differentiate smaller devices such as those of the NEC UltraLite and Compaq LTE series in 1989, which were, in contrast to previous laptops, the approximate size of an A4 paper sheet. Either term is often used improperly: due to heat and other issues, many laptops are inappropriate for use on one's lap, and most are not the size of an A4 sheet. Although, some older portable computers, such as the Macintosh Portable and certain Zenith TurbosPort models, were sometimes described as "laptops", their size and weight were too great for this category.