LAPTOP
A laptop is a personal computer designed for mobile use and small and light enough to sit on a person's lap while in use. A laptop integrates most of the typical components of a desktop computer, including a display, a keyboard, a pointing device (a touchpad, also known as a track pad, and/or a pointing stick), speakers, and often including a battery, into a single small and light unit. The rechargeable battery (if present) is charged from an AC adapter and typically stores enough energy to run the laptop for three to five hours in its initial state, depending on the configuration and power management of the computer.
Laptops are usually notebook-shaped with thicknesses between 0.7–1.5 inches (18–38 mm) and dimensions ranging from 10x8 inches (27x22cm, 13" display) to 15x11 inches (39x28cm, 17" display) and up. Modern laptops weigh 3 to 12 pounds (1.4 to 5.4 kg); older laptops were usually heavier. Most laptops are designed in the flip form factor to protect the screen and the keyboard when closed. Modern tablet laptops have a complex joint between the keyboard housing and the display, permitting the display panel to swivel and then lie flat on the keyboard housing.
HISTORY:
As the personal computer became feasible in the early 1970s, the idea of a portable personal computer followed. A "personal, portable information manipulator" was imagined by Alan Kay at Xerox PARC in 1968 and described in his 1972 paper as the "Dynabook".
As 8-bit CPU machines became widely accepted, the number of portables increased rapidly. The Osborne 1, released in 1981, used the Zilog Z80 and weighed 23.5 pounds (10.7 kg). It had no battery, a 5 in (13 cm) CRT screen and dual 5.25 in (13.3 cm) single-density floppy drives. In the same year the first laptop-sized portable computer, the Epson HX-20, was announced. The Epson had a LCD screen, a rechargeable battery and a calculator-size printer in a 1.6 kg (3.5 lb) chassis. BothTandy/RadioShack and HP also produced portable computers of varying designs during this period.
CLASSIFICATIONS
The general term "laptop" can be used to refer to a number of classes of small portable computers:
§ Notebook – A laptop PC which measures at least 11 inches across, which is the minimum width to allow for a full-size keyboard (a keyboard with the minimum QWERTY key layout, which is at least 13-1/2 keys across that are on three-quarter (0.750) inch centers, plus some room on both ends for the case). The first Notebook PC's were the size of a standard U.S.
notebook piece of paper (8-1/2 x 11 inches), but later "A4-size" Notebook PC's were introduced, which were the width of a standard European "A4" notebook piece of paper (297 mm, or about 11.7 inches wide), and added a vertical column of keys to the right and wider screens.
§ Sub-Notebook or Netbook – A laptop PC which is less than 11 inches wide, which means it has less than a full-size keyboard (measured in percentage of full-size, such as 92%), and therefore also less display screen width, compared to a Notebook PC. It also is usually lower cost, more lightweight, and has less features than a Notebook PC. The tradeoff is that a smaller than full-size keyboard can be more difficult to operate, especially if you have larger hands.
§ Ultra-thin Laptop - A newer class of laptops which is very thin and lightweight.
§ Tablet PC – Has a small, "calculator-type" or "chiclet" keyboard, and/or touch-screen interface.
§ Rugged – Engineered to operate in tough conditions (strong vibrations, extreme temperatures, wet and dusty environments).
DESKTOP REPLACEMENT
A desktop replacement computer is a laptop that provides most of the capabilities of a desktop computer, with a similar level of performance. Desktop replacements are usually larger and heavier than standard laptops. They contain more powerful components and have a 15" or larger display. Because of their bulk, they are not as portable as other laptops and their operation time on batteries is typically shorter; instead, they are meant to be used as a more compact, easier to carry alternative to a desktop computer
ADVANTAGES
Portability is usually the first feature mentioned in any comparison of laptops versus desktop PCs
Productivity – Using a laptop in places where a desktop PC can't be used, and at times that would otherwise be wasted
Immediacy – Carrying a laptop means having instant access to various information, personal and work files
Up-to-date information – If a person has more than one desktop PC, a problem of synchronization arises: changes made on one computer are not automatically propagated to the others
Etc;
DISADVANTAGES
Compared to desktop PCs, laptops have disadvantages in the following fields:
Upgradeability
Performance
Security
Etc;
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