Classification
The term "laptop" can refer to a number of classes of small portable computers:[10][11]
Full-size Laptop: A laptop large enough to accommodate a "full-size" keyboard (a keyboard with the minimum QWERTY key layout, which is at least 13.5 keys across that are on ¾ (0.750) inch centers, plus some room on both ends for the case). The measurement of at least 11 inches across has been suggested as the threshold for this class.[12] The first laptops were the size of a standard U.S. "A size" notebook sheet of paper (8.5 × 11 inches)[citation needed], but later "A4-size" laptops were introduced, which were the width of a standard ISO 216 A4 sheet of paper (297 mm, or about 11.7 inches), and added a vertical column of keys to the right and wider screens. It can also be laid sideways when not in use.
Netbook: A smaller, lighter, more portable laptop. It is also usually cheaper than a full-size laptop, but sometimes has fewer features and less computing power. Smaller keyboards can be more difficult to operate. There is no sharp line of demarcation between netbooks and inexpensive small laptops; some 11.6" models are marketed as netbooks. Since netbook laptops are quite small in size, netbooks typically do not come with an internal optical drive.
Tablet PC: these have touch screens. There are "convertable tablets" with a full keyboard where the screen rotates to be used atop the keyboard, and "slate" form-factor machines which are usually touch-screen only (although a few older