A special-purpose computer that sacrifices some storage and processing capabilities in order to maintain a low weight.

A subnotebook (also known as a kneetop or an ultraportable) is an extremely small and lightweight portable computer, with most of the features of a standard laptop computer and running all its applications. Its overall size is much smaller than an A4 paper notebook (8.27"×11.69"), but they are often somewhat larger than a handheld computer. Hence it often has smaller than 10" (diagonal) screen and weigh less than 1 kg; as opposed to full-size laptop with 15" screen and weighing 2 kg or more.