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A laptop computer or simply laptop (also notebook computer or notebook) is a small mobile personal computer, usually weighing from one to three kilograms, depending on size, materials and other factors.

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 Compaq LTE series in 1989, which were, in contrast to previous laptops, the approximate size of an A4 paper sheet.[1] 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.

Laptops usually run on a single battery or from an external AC/DC adapter which can charge the battery while also supplying power to the computer itself.

An Acer laptop with touchpadAs personal computers, laptops are capable of the same tasks as a desktop PC, although they are typically less powerful for the same price. They contain components that are similar to their desktop counterparts and perform the same functions, but are miniaturized and optimized for mobile use and efficient power consumption. Laptops usually have liquid crystal displays and most of them use different memory modules for their RAM (for instance, SO-DIMM in lieu of the larger DIMMs). In addition to a built-in keyboard, they may utilize a touchpad (also known as a trackpad) or a pointing stick for input, though an external keyboard or mouse can usually be attached.

Categories
Terms sometimes used for subtypes of laptop computers include:

Ultraportables
Laptops with screens typically less than 12 inches diagonally and a weight of less than 1.7kg. Their primary audience is usually business travellers, who need small, light laptops. Ultraportables are often very expensive and house power-saving CPUs and almost always have integrated graphics.
Thin-and-lights
Laptops usually weighing in between 1.8kg and 2.8kg with a screen size of between 12 and 14 inches diagonally.
Medium-sized laptops
These usually have screens of 15 – 15.4 inches diagonally and a weight of around 3-3.5kg. They usually sacrifice a little computing power for smaller dimensions and longer battery life, although the length and width are usually determined by the screen size.
Desktop replacement computers
Powerful laptops meant to be mainly used in a fixed location and infrequently carried out due to their weight and size; the latter provides more space for powerful components and a big screen, usually measuring 15 inches or more. Desktop replacements tend to have limited battery life, rarely exceeding three hours, because the hardware does not optimize power efficiency.
History
Before laptop/notebook computers were technically feasible, similar ideas had been proposed, most notably Alan Kay’s Dynabook concept, developed at Xerox PARC in the early 1970s.

The first commercially available portable computer was the Osborne 1 in 1981, which used the CP/M operating system. Although it was large and heavy compared to today’s laptops, with a tiny CRT monitor, it had a near-revolutionary impact on business, as professionals were able to take their computer and data with them for the first time. This and other “luggables” were inspired by what was probably the first portable computer, the Xerox NoteTaker, again developed at Xerox PARC, in 1976; however, only ten prototypes were built. The Osborne was about the size of a portable sewing machine, and importantly could be carried on a commercial aircraft. However, it was not possible to run the Osborne on batteries; it had to be plugged in.

A more enduring success was the Compaq Portable, the first product from Compaq, introduced in 1983, by which time the IBM Personal Computer had become the standard platform. Although scarcely more portable than the Osborne machines, and also requiring AC power to run, it ran MS-DOS and was the first true IBM clone (IBM’s own later Portable Computer, which arrived in 1984, was notably less IBM PC-compatible than the Compaq[citation needed]).

Another significant machine announced in 1981, although first sold widely in 1983, was the Epson HX-20. A simple handheld computer, it featured a full-transit 68-key keyboard, rechargable nickel-cadmium batteries, a small (120 x 32-pixel) dot-matrix LCD display with 4 lines of text, 20 characters per line text mode, a 24 column dot matrix printer, a Microsoft BASIC interpreter, and 16 kB of RAM (expandable to 32 kB).

However, arguably the first true laptop was the GRiD Compass 1101, designed by Bill Moggridge in 1979-1980, and released in 1982. Enclosed in a magnesium case, it introduced the now familiar clamshell design, in which the flat display folded shut against the keyboard. The computer could be run from batteries, and was equipped with a 320