AskDefine | Define laptop

Dictionary Definition

laptop n : a portable computer small enough to use in your lap [syn: laptop computer]

User Contributed Dictionary

English

Etymology

lap + top

Related terms

Translations

computing: a laptop computer

Extensive Definition

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. Many computers also have a 3 volt cell to run the clock and other processes in the event of a power failure.
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.

History

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.

Types

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.

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.
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.

Subnotebook

Laptops weighing typically between 4.6 and 6 lb (1.8–2.7 kg) and a screen of 14.1 to 15.4 inches (35.81–39.12 cm) 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.

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. However, higher end laptops can come with dedicated graphics processors, such as the Dell Inspiron E1505 and E1705, which can be bought with an ATI Mobility Radeon X1300 or similar or the MacBook Pro which comes standard with an nVidia 8600M GT. 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. However, the PowerPC G3 and G4 processor generations were able to offer almost the same performance as their desktop versions, limited mostly by other factors, such as the system bus bandwidth; recently, though, with the introduction of the G5s, they have been far outstripped. At one point, the Pismo G3, at up to 500 MHz, was faster than the fastest desktop G3 (then the B&W G3), which ran at 450 MHz.
Some parts for a modern laptop have no corresponding part in a desktop computer. For example, current models use lithium ion and more recently lithium polymer batteries, which have largely replaced the older nickel metal-hydride technology. 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. Due to their portability and tight integration, laptops are more subject to wear and physical damage than desktops. Components such as batteries, screen hinges, power jacks, and power cords are commonly subject to deterioration due to ordinary use. These components are usually expensive to replace, with a typical laptop battery costing US$130, the AC Adapter US$75. Other parts are inexpensive such as a power jack costing perhaps US$20, but replacement may require extensive disassembly and reassembly of layers of internal components. Other inexpensive but fragile parts often cannot be purchased separate from larger more expensive components. For example, the video display cable and backlight power cable that passes through the lid hinges to operate the screen will eventually break from opening and closing the lid hundreds of times over many years, and usually these tiny cables cannot be purchased separate from an entire US$400 LCD panel.
A liquid spill onto the keyboard, which is rather a minor mishap with a desktop system can damage costly components such as the motherboard or LCD panel. Dropping a laptop can damage the LCD screen if not break apart its body. The repair costs of a failed motherboard or LCD panel may exceed the purchase value of the laptop.
Laptops must also rely on extremely compact cooling systems involving a fan and heatsink that eventually fails due to filling with airborne dust and debris. Most laptops do not have any sort of removable dust collection filter over the air intake for these cooling systems, resulting in a system that gradually runs hotter and louder as the years pass. Eventually the laptop cooling is so choked with dust that it starts to overheat just from minor operational load. This dust is usually deeply buried inside where casual cleaning and vacuuming cannot remove it, and instead complete disassembly is needed to clean the laptop.

Ruggedized Laptops

Some manufacturers have mitigated some of these problems by selling "ruggedized" laptops. These often have a rubberized sheeting under the keyboard keys and special drain that safely routes all of the water out through a hole in the bottom of the case.
Additionally, the bodies of these laptops are typically made of a stiffer magnesium alloy instead of plastic, since it is the flexing of the circuit boards and fragile mechanical devices that causes the most damage. Hard drives are often mounted in soft shock-absorbing silicone mounts to greatly increase their chances of surviving a waist-high fall.
When a laptop hits the floor, the free-floating hard drive heads can slap against the spinning platter, scratching it and cause an irrepairable head crash that renders the hard drive unusable. Recently hard drives have been constructed which can move the read heads completely off the spinning platters, known as unloading. With the use of an accelerometer, the hardware can detect the sudden fall and park the heads off-platter before the laptop hits the ground. (See Sudden Motion Sensor.)

Advantages

The main advantage of laptops over their larger desktop counterparts is the inherent portability. Another advantage is the laptop's ability to operate on battery power in the case of a power outage and less energy consumption.

Upgradeability

Laptops' upgradeability is severely limited, both for technical and economic reasons. As of 2006, there is no industry-wide standard form factor for laptops. Each major laptop vendor pursues its own proprietary design and construction, with the result that laptops are difficult to upgrade and exhibit high repair costs. With few exceptions, laptop components can rarely be swapped between laptops of competing manufacturers, or even between laptops from the different product-lines of the same manufacturer. Standard feature peripherals (such as audio, video, USB, 1394, WiFi, Bluetooth) are generally integrated on the main PCB (motherboard), and thus upgrades often require using external ports, card slots, or wireless peripherals. Other components, such as RAM modules, hard drives, and batteries are typically user-upgradeable.
Many laptops have removable CPUs, although support for other CPUs is restricted to the specific models supported by the laptop motherboard. The socketed CPUs are perhaps for the manufacturer's convenience, rather than the end-user, as few manufacturers try new CPUs in last year's laptop model with an eye toward selling upgrades rather than new laptops. In many other laptops, the CPU is soldered and non-replaceable.
Many laptops also include an internal MiniPCI slot, often occupied by a Wi-Fi or Bluetooth card, but as with the CPU, the internal slot is often restricted in the range of cards that can be installed. The widespread adoption of USB mitigates I/O connectivity to a great degree, although the user must carry the USB peripheral as a separate item.
NVidia and ATI have proposed a standardized interface for laptop GPU upgrades (such as an MXM), but again, choices are limited compared to the desktop PCIe/AGP after-market.
In January 2007, Asus announced XG Station external video card for laptops. XG Station is connected to the laptops using USB-2 and Express card interface.
In February 2007, a new standard for external PCI Express cables and connectors was announced. Future laptops can be expanded using external PCI Express backplane and chassis.

Performance

For a given price range (and manufacturing base), laptop computational power has traditionally trailed that of desktops. This is partly due to most laptops sharing RAM between the program memory and the graphics adapter. By virtue of their usage goals, laptops prioritize energy efficiency and compactness over absolute performance. Desktop computers and their modular components are built to fit much bigger standard enclosures, along with the expectation of AC line power. As such, energy efficiency and portability for desktops are secondary design goals compared to absolute performance.
For typical home (personal use) applications, where the computer spends the majority of its time sitting idle for the next user input, laptops of the thin-client type or larger are generally fast enough to achieve the required performance. 3D gaming, multimedia (video) encoding and playback, and analysis-packages (database, math, engineering, financial, etc.) are areas where desktops still offer the casual user a compelling advantage.
With the advent of dual-core processors and perpendicular recording, laptops are beginning to close the performance gap with desktops. Intel's Core 2 line of processors is efficient enough to be used in portable computers, and many manufacturers such as Apple, Lenovo and Dell are building Core 2 based laptops. Also, many high end laptop computers feature mobility versions of graphics cards, eliminating the performance losses associated with integrated graphics.

Health issues

A study by State University of New York researchers says heat generated from laptops can significantly elevate the temperature of the scrotum, potentially putting sperm count at risk. The small study, which included little more than two dozen men ages 13 to 35, found that the sitting position required to balance a laptop can raise scrotum temperature by as much as 2.1 °C (3.8 °F). Heat from the laptop itself can raise the temperature by another 0.7 °C (1.4 °F), bringing the potential total increase to 2.8 °C (5.2 °F). However, further research is needed to determine whether this directly affects sterility in men. A common practical solution to this problem is to place the laptop on a table or desk.
Heat from using laptop on lap can also cause skin discoloration on the thighs.
Because of their small keyboard and trackpad pointing devices, the use of laptops can cause RSI, and for this reason laptops have docks that are used with ergonomic keyboards to prevent injury. The integrated screen often causes users to hunch over for a better view, which can cause neck or spinal injuries. Some health standards require that ergonomic keyboards be used in workplaces.

Security

Laptops are generally prized targets of theft, and theft of laptops can lead to more serious problems such as identity theft from stolen credit card numbers. Most laptops have a Kensington security slot to chain the computer to a desk with a third party security cable. In addition to this, modern operating systems and software may have disk encryption functionality that renders the data on the laptop's hard drive unreadable without a key.

Related devices

A laptop can use the same software as a desktop machine but is small enough to support mobile computing and operate on battery power. Devices that are similar to a laptop include:
Boundaries that separate these categories are blurry at times. For example, the OQO UPC is a PDA-sized tablet PC; the Apple eMate had the clamshell form factor of a laptop, but ran PDA software. The HP Omnibook line of laptops included some devices small enough to be called handheld computers. The hardware of the Nokia 770 internet tablet is essentially the same as that of a PDA such as the Zaurus 6000; the only reason it's not called a PDA is that it doesn't have PIM software. On the other hand, both the 770 and the Zaurus can run some desktop Linux software, usually with modifications.

Major brands and manufacturers

summary="Links to Wikipedia articles about laptop manufacturers. For some of them, articles about the company's most well-known models or series are linked as well." Major brands

References

External links

laptop in Amharic: ላፕቶፕ
laptop in Arabic: حاسوب محمول
laptop in Bengali: ল্যাপটপ কম্পিউটার
laptop in Bosnian: Laptop
laptop in Bulgarian: Преносим компютър
laptop in Catalan: Ordinador portàtil
laptop in Czech: Notebook
laptop in Welsh: Gliniadur
laptop in Danish: Bærbar computer
laptop in German: Notebook
laptop in Modern Greek (1453-): Φορητός υπολογιστής
laptop in Spanish: Computadora portátil
laptop in Estonian: Sülearvuti
laptop in Esperanto: Tekokomputilo
laptop in French: Ordinateur portable
laptop in Galician: Portátil
laptop in Korean: 노트북 컴퓨터
laptop in Hindi: लैपटॉप
laptop in Indonesian: Komputer jinjing
laptop in Icelandic: Fartölva
laptop in Italian: Computer portatile
laptop in Hebrew: מחשב נייד
laptop in Latvian: Klēpjdators
laptop in Hungarian: Notebook
laptop in Malayalam: ലാപ്‌ടോപ്പ്
laptop in Marathi: लॅपटॉप
laptop in Malay (macrolanguage): Komputer riba
laptop in Dutch: Laptop
laptop in Japanese: ラップトップパソコン
laptop in Japanese: ノートパソコン
laptop in Norwegian: Bærbar datamaskin
laptop in Polish: Laptop
laptop in Portuguese: Laptop
laptop in Russian: Ноутбук
laptop in Simple English: Laptop
laptop in Slovak: Notebook
laptop in Slovenian: Prenosnik
laptop in Finnish: Kannettava tietokone
laptop in Swedish: Bärbar dator
laptop in Tamil: மடிக்கணினி
laptop in Thai: แล็ปท็อป
laptop in Vietnamese: Máy tính xách tay
laptop in Turkish: Dizüstü bilgisayar
laptop in Ukrainian: Ноутбук
laptop in Yiddish: שויס קאמפיוטער
laptop in Chinese: 筆記型電腦
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