A laptop computer or simply laptop (also notebook computer, notebook and notepad) is a small mobile computer, typically weighing 3-12 pounds (around 1.3 to 5.4 kilograms), although older laptops may weigh more.
Laptops usually run on a single main battery or from an external AC/DC adapter that charges the battery while also supplying power to the computer itself even in the event of a power failure. This very powerful main battery should not be confused with smaller 3 volt cell battery that is built in nearly every computer. This small battery is intended to to run the real-time clock and backup BIOS configuration into the CMOS memory during the time the computer is not powered on and/or is not connected to the external power.
Laptops 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, although typically less powerful for the same price. Laptops usually have liquid crystal displays and most of them use different memory modules for their random access memory (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.
Laptops began from a desire to have a full-featured computer that could be easily used anywhere. Their predecessor was called the luggable. These all-in-one systems could be easily transported, but were heavy and usually were not battery powered. The CRT was one of the major reasons luggables were so large and heavy, but the use of a full-size desktop motherboard with room for ISA expansion cards was another size factor.
It was the transition to LCD and plasma displays that permitted the luggable to shrink in size and become the first real laptop, though at first still without internal batteries. Battery technology improvements and the introduction of smaller devices such as the 3.5-inch floppy disk permitted a gradually more compact and sophisticated complete portable system.
Mainstream
Laptops weighing between 5 and 7 lb (2.3–3.2 kg) with a screen size of 14.1 or 15.4 inches (35 or 39 cm) diagonally.
[edit] Desktop replacement
A desktop replacement computer is a personal computer that provides the full capabilities of a desktop computer while remaining portable. They are often a larger, bulkier laptop. Because of their increased size, this class of computer usually includes more powerful components and a larger display than generally used in smaller portable computers and can have a relatively limited battery capacity (or none at all). Some use a limited range of desktop components to provide better performance per dollar at the expense of battery life. These are sometimes called desknotes, a portmanteau of the words "desktop" and "notebook," though the term is also applied to desktop replacement computers in general.[1]
Powerful laptops meant to be mainly used for fun and infrequently carried out due to their weight and size; the latter provides more space for powerful components and a big screen, usually measuring 17–20 inches (43–51 cm). Desktop replacements tend to have limited battery life, rarely exceeding three hours, because the hardware is not optimized for efficient power usage. Sometimes called a luggable laptop. An example of a desktop replacement computers are gaming notebooks, which are designed to handle 3D graphic-intensive processing for gamers.
[edit] Subnotebook
Laptops weighing typically between 4.6 and 6 lb (1.8–2.7 kg) and a screen of 10.6 to 13.3 inches diagonally. A subnotebook is a small and lightweight portable computer, with most of the features of a standard laptop computer but smaller. The term is often applied to systems that run full versions of desktop operating systems such as Windows or Linux, rather than specialized software such as Windows CE, Palm OS or Internet Tablet OS.
Subnotebooks are smaller than laptops but larger than handheld computers and UMPCs. They often have screens that are 26.92 cm (10.6") (diagonal) or more, and a weight less than 1 up to about 2 kg; as opposed to full-size laptops with 35.81 cm (14.1") or 39.12 cm (15.4") screens and weighing 2 kg or more. The savings in size and weight are usually achieved partly by omitting ports or having removable media/optical drives; subnotebooks are often paired with docking stations to compensate.
Subnotebooks have been something of a niche computing product and have rarely sold in large numbers until the 2007 introduction of the Asus Eee PC and the OLPC XO-1.[2]
[edit] Parts
Most modern laptops feature 12 inch (30 cm) or larger active matrix displays with resolutions of 1024×768 pixels and above, and have a PC Card (formerly PCMCIA) or ExpressCard expansion bay for expansion cards. Internal hard disks are physically smaller—2.5 inch (60 mm)—compared to the standard desktop 3.5 inch (90 mm) drive, and usually have lower performance and power consumption. Video and sound chips are usually integrated. This tends to limit the use of laptops for gaming and entertainment, two fields which have constantly escalating hardware demands,[3] however, higher end laptops can come with dedicated graphics processors. These mobile graphics processors tend to have less performance than their desktop counterparts, but this is because they have been optimized for lower power usage.
There is a wide range of laptop specific processors available from Intel (Pentium M, Celeron, Intel Core and Intel Core 2), AMD (Athlon, Turion 64, and Sempron) and from VIA (C3 and C7-M). Motorola and IBM developed and manufactured the chips for the former PowerPC-based Apple laptops (iBook and PowerBook). Generally, laptop processors are less powerful than their desktop counterparts, due to the need to save energy and reduce heat dissipation.
Current models of laptops utilize lithium ion batteries with more recent models using the new lithium polymer technology. These technologies have largely replaced the older nickel metal-hydride batteries. Typical battery life for most laptops is two to five hours with light-duty use, but may drop to as little as one hour with intensive use. Batteries gradually deteriorate over time and eventually need to be replaced in one to five years, depending on the charging and discharging pattern.
Docking stations became another common laptop accessories in the early 1990s. They typically were quite large and offered 3.5" and 5.25" storage bays, one to three expansion slots (typically AT style), and a host of connectors. The mating between the laptop and docking station was typically through a large, high-speed, proprietary connector. The most common use was in a corporate computing environment where the company had standardized on a common network card and this same card was placed into the docking station. These stations were very large and quite expensive. As the need to additional storage and expansion slots became less critical because of the high integration inside the laptop itself, the emergence of the Port Replicator as a major accessory commenced. The Port Replicator was often a passive device that simply mated to the connectors on the back of the notebook and allowed the user to quickly connect their laptop so VGA, PS/2, RS-232, etc. devices were instantly attached. As higher speed ports like USB and Firewire became commonplace, the Port Replication was accomplished by a small cable connected to one of the USB 2.0 or FireWire ports on the notebooks. Wireless Port Replicators followed.
Virtually all laptops can be powered from an external AC converter. This device typically adds half a kilogram (1 lb) to the overall "transport weight" of the equipment.
A pointing stick or touchpad is used to control the position of the cursor on the screen. The pointing stick is usually a rubber dot that is located between the G, H and B keys on the laptop keyboard. To navigate the cursor, pressure is applied in the direction intended to move. The touchpad is touch-sensitive and the cursor can be navigated by moving the finger on the pad.
Intel, Asus, Compal, Quanta and other laptop manufacturers have created Common Building Block standard for laptop parts.
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