A laptop is a personal computer designed for mobile use small enough to sit on one's lap.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 trackpad, 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 two to three hours in its initial state, depending on the configuration and power management of the computer.
Laptops are usually shaped like a large notebook 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 twist and then lay flat on the keyboard housing. They usually have a touchscreen display and some include handwriting recognition or graphics drawing capability.
Laptops were originally considered to be "a small niche market" and were thought suitable mostly for "specialized field applications" such as "the military, the Internal Revenue Service, accountants and sales representatives". But today, there are already more laptops than desktops in businesses, and laptops are becoming obligatory for student use and more popular for general use. In 2008 more laptops than desktops were sold in the US and it has been predicted that the same milestone will be reached in the worldwide market as soon as late 2009.
Classification
The general terms "laptop" or "notebook" can be used to refer to a number of classes of small portable computers:
By purpose and (approximately) by screen size:
Desktop replacement – emphasizes performance, is less portable, 15" and larger screen;
Standard laptop – balances portability and features, 13-15" screen;
Subnotebook – emphasizes portability, has fewer features, 13" or smaller screen.
By features:
Budget – a cheap, lower-performance standard-sized laptop;
Tablet PC – Has a touch-screen interface, may or may not have a keyboard;
Netbook – A cheaper, smaller version of a subnotebook suited to Internet surfing and basic office applications. Usually has a 9" screen.
Gaming laptop - A larger laptop with a powerful graphics card for playing graphics-intensive computer games.
Rugged – Engineered to operate in tough conditions (strong vibrations, extreme temperatures, wet and dusty environments).
Desktop Replacement
Dell XPS M140 Laptop.
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.
Some laptops in this class use a limited range of desktop components to provide better performance for the same price at the expense of battery life; in a few of those models, there is no battery at all and the laptop can only be used when plugged in. These are sometimes called desknotes, a portmanteau of the words "desktop" and "notebook," though the term can also be applied to desktop replacement computers in general.
In the early 2000s, desktops were more powerful, easier to upgrade, and much cheaper in comparison with laptops. But in the last few years, the advantages have drastically changed or shrunk since the performance of laptops has markedly increased. In the second half of 2008, laptops have finally outsold desktops for the first time ever. In the U.S., the PC shipment declined 10 percent in the fourth quarter of 2008. In Asia, the worst PC shipment growth went up 1.8 percent over the same quarter the previous year since PC statistics research started.
The names "Media Center Laptops" and "Gaming Laptops" are also used to describe specialized members of this class of notebooks.
Subnotebook
Sony VAIO C1 subnotebook.
A subnotebook, also called an ultraportable by some vendors, is a laptop designed and marketed with an emphasis on portability (small size, low weight and long battery life) that retains the performance of a standard notebook. Subnotebooks are usually smaller and lighter than standard laptops, weighing between 0.8 and 2 kg (2 to 5 pounds);the battery life can exceed 10 hours when a large battery or an additional battery pack is installed.
To achieve the size and weight reductions, ultraportables use high resolution 13" and smaller screens (down to 6.4"), have relatively few ports, employ expensive components designed for minimal size and best power efficiency, and utilize advanced materials and construction methods. Some subnotebooks achieve a further portability improvement by omitting an optical/removable media drive; in this case they may be paired with a docking station that contains the drive and optionally more ports or an additional battery.
The term "subnotebook" is usually reserved to laptops that run general-purpose desktop operating systems such as Windows, Linux or Mac OS X, rather than specialized software such as Windows CE, Palm OS or Internet Tablet OS.
Netbook
An Asus Eee PC netbook.
Netbooks are laptops that are light-weight, economical, energy-efficient and especially suited for wireless communication and Internet access.Hence the name netbook (as "the device excels in web-based computing performance") rather than notebook which pertains to size.
Especially suited for web browsing and e-mailing, netbooks "rely heavily on the Internet for remote access to web-based applications".and are targeted increasingly at cloud computing users who rely on servers and require a less powerful client computer.While the devices range in size from below 5 inches to over 12, most are between 7 and 11 inches and weigh between 2 and 3 pounds.
Netbooks normally use light-weight operating systems including Linux and Windows XP rather than more resource-intensive operating systems like Windows Vista, as they have less processing power than traditional laptops.
Recently Google has signalled its intention to develop its own Chrome operating system for this market.
Rugged laptop
A Panasonic Toughbook.
A rugged (or ruggedized) laptop is designed to reliably operate in harsh usage conditions such as strong vibrations, extreme temperatures, and wet or dusty environments. Rugged laptops are usually designed from scratch, rather than adapted from regular consumer laptop models. Rugged notebooks are bulkier, heavier, and much more expensive than regular laptops, and thus are seldom seen in regular consumer use.
The design features found in rugged laptops include rubber sheeting under the keyboard keys, sealed port and connector covers, passive cooling, superbright displays easily readable in daylight, cases and frames made of magnesium alloys that are much stronger than plastic found in commercial laptops, and solid-state storage devices or hard disc drives that are shock mounted to withstand constant vibrations. Rugged laptops are commonly used by public safety services (police, fire and medical emergency), military, utilities, field service technicians, construction, mining and oil drilling personnel. Rugged laptops are usually sold to organizations, rather than individuals, and are rarely marketed via retail channels.
Components
Miniaturization: a comparison of a desktop computer motherboard (ATX form factor) to a motherboard from a 13" laptop (2008 unibody Macbook)
Inner view of a Sony Vaio laptop
The basic components of laptops are similar in function to their desktop counterparts, but are miniaturized, adapted to mobile use, and designed for low power consumption. Because of the additional requirements, laptop components are usually of inferior performance compared to similarly priced desktop parts. Furthermore, the design bounds on power, size, and cooling of laptops limit the maximum performance of laptop parts compared to that of desktop components.
The following list summarizes the differences and distinguishing features of laptop components in comparison to desktop personal computer parts:
Motherboard – Laptop motherboards are highly make and model specific, and do not conform to a desktop form factor. Unlike a desktop board that usually has several slots for expansion cards (3 to 7 are common), a board for a small, highly integrated laptop may have no expansion slots at all, with all the functionality implemented on the motherboard itself; the only expansion possible in this case is via an external port such as USB. Other boards may have one or more standard, such as ExpressCard, or proprietary expansion slots. Several other functions (storage controllers, networking, sound card and external ports) are implemented on the motherboard.
Central processing unit (CPU) – Laptop CPUs have advanced power-saving features and produce less heat than desktop processors, but are not as powerful.There is a wide range of CPUs designed for laptops available from Intel (Pentium M, Celeron M, Intel Core and Core 2 Duo), AMD (Athlon, Turion 64, and Sempron), VIA Technologies, Transmeta and others. On the non-x86 architectures, Motorola and IBM produced the chips for the former PowerPC-based Apple laptops (iBook and PowerBook). Some laptops have removable CPUs, although support by the motherboard may be restricted to the specific models.In other laptops the CPU is soldered on the motherboard and is non-replaceable.
A SODIMM memory module.
Memory (RAM) – SO-DIMM memory modules that are usually found in laptops are about half the size of desktop DIMMs. They may be accessible from the bottom of the laptop for ease of upgrading, or placed in locations not intended for user replacement such as between the keyboard and the motherboard. Currently, most midrange laptops are factory equipped with 3-4 GB of DDR2 RAM, while some higher end notebooks feature up to 8 GB of DDR3 memory. Netbooks however, are commonly equipped with only 1 GB of RAM to keep manufacturing costs low.
Expansion cards – A PC Card (formerly PCMCIA) or ExpressCard bay for expansion cards is often present on laptops to allow adding and removing functionality, even when the laptop is powered on. Some subsystems (such as Ethernet, Wi-Fi, or a cellular modem) can be implemented as replaceable internal expansion cards, usually accessible under an access cover on the bottom of the laptop. Two popular standards for such cards are MiniPCI and its successor, the PCI Express Mini.
Power supply – Laptops are typically powered by an internal rechargeable battery that is charged using an external power supply. The power supply can charge the battery and power the laptop simultaneously; when the battery is fully charged, the laptop continues to run on AC power. The charger adds about 400 grams (1 lb) to the overall "transport weight" of the notebook.
Battery – Current laptops utilize lithium ion batteries, with more recent models using the new lithium polymer technology. These two technologies have largely replaced the older nickel metal-hydride batteries. Typical battery life for standard laptops is two to five hours of light-duty use, but may drop to as little as one hour when doing power-intensive tasks. A battery's performance gradually decreases with time, leading to an eventual replacement in one to three years, depending on the charging and discharging pattern. This large-capacity main battery should not be confused with the much smaller battery nearly all computers use to run the real-time clock and to store the BIOS configuration in the CMOS memory when the computer is off. Lithium-ion batteries do not have a memory effect as older batteries may have. The memory effect happens when one does not use a battery to its fullest extent, then recharges the battery. New innovations in laptops and batteries have seen new possible matchings which can provide up to a full 24 hours of continued operation, assuming average power consumption levels. An example of this is the HP EliteBook 6930p when used with its ultra-capacity battery.
Video display controller – On standard laptops the video controller is usually integrated into the chipset. This tends to limit the use of laptops for gaming and entertainment, two fields which have constantly escalating hardware demands. Higher-end laptops and desktop replacements in particular often come with dedicated graphics processors on the motherboard or as an internal expansion card. These mobile graphics processors are comparable in performance to mainstream desktop graphic accelerator boards.
Display – Most modern laptops feature 12 inches (30 cm) or larger color active matrix displays with resolutions of 1280x800 (16:10) or 1366 x 768 (16:9) pixels and above. Many current models use screens with higher resolution than typical for desktop PCs (for example, the 1440×900 resolution of a 15" Macbook Pro can be found on 19" widescreen desktop monitors).
A size comparison of 3.5" and 2.5" hard disk drives
Removable media drives – A DVD/CD reader/writer drive is typically standard. CD drives are becoming rare, while Blu-Ray is becoming more common on notebooks.Many ultraportables and netbooks either move the removable media drive into the docking station or exclude it altogether.
Internal storage – Laptop hard disks are physically smaller—2.5 inches (64 mm) or 1.8 inches (46 mm) —compared to desktop 3.5 inches (89 mm) drives. Some newer laptops (usually ultraportables) employ more expensive, but faster, lighter and power-efficient flash memory-based SSDs instead. Currently, 250 to 320 GB sizes are common for laptop hard disks (64 to 128 GB for SSDs).
Input – A pointing stick, touchpad or both are used to control the position of the cursor on the screen, and an integrated keyboard is used for typing. An external keyboard and/or mouse may be connected using USB or PS/2 (if present).
Ports – several USB ports, an external monitor port (VGA or DVI), audio in/out, and an Ethernet network port are found on most laptops. Less common are legacy ports such as a PS/2 keyboard/mouse port, serial port or a parallel port. S-video or composite video ports are more common on consumer-oriented notebooks.
Docking stations
A docking station is a relatively bulky laptop accessory that contains multiple ports, expansion slots, and bays for fixed or removable drives. A laptop connects and disconnects easily to a docking station, typically through a single large proprietary connector. A port replicator is a simplified docking station that only provides connections from the laptop to input/output ports. Both docking stations and port replicators are intended to be used at a permanent working place (a desk) to offer instant connection to multiple input/output devices and to extend a laptop's capabilities.
Docking stations became a common laptop accessory in the early 1990s. 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 for additional storage and expansion slots became less critical because of the high integration inside the laptop, port replicators have gained popularity, being a cheaper, often passive device that often simply mates to the connectors on the back of the notebook, or connects via a standardised port such as USB or FireWire.
Standards
Some laptop components (optical drives, hard drives, memory and internal expansion cards) are relatively standardized, and it is possible to upgrade or replace them in many laptops as long as the new part is of the same type. Subtle incompatibilities and variations in dimensions, however, are not uncommon.Depending on the manufacturer and model, a laptop may range from having several standard, easily customizable and upgradeable parts to a proprietary design that cannot be reconfigured at all.
In general, components other than the four categories listed above are not intended to be replaceable, and thus rarely follow a standard. In particular, motherboards, locations of ports, and design and placement of internal components are usually make and model specific. Those parts are neither interchangeable with parts from other manufacturers nor upgradeable. If broken or damaged, they must be substituted with an exact replacement part. Those users uneducated in the relevant fields are those the most affected by incompatibilities, especially if they attempt to connect their laptops with incompatible hardware or power adapters.
Intel, Asus, Compal, Quanta and other laptop manufacturers have created the Common Building Block standard for laptop parts to address some of the inefficiencies caused by the lack of standards.
