LaptopLaptop
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A laptop computer, also known as a notebook computer, is a small personal computer designed for mobile use. A laptop integrates all of the typical components of a desktop computer, including a display, a keyboard, a pointing device (a touchpad, also known as a trackpad, or a pointing stick) and a battery into a single portable unit. The rechargeable battery is charged from an AC/DC adapter and has enough capacity to power the laptop for several hours.
A laptop is usually shaped like a large notebook with thickness of 0.7-1.5 inches (1.7-4cm) 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), and some older laptops were even heavier. Most laptops are designed in the flip form factor to protect the screen and the keyboard when closed.
Originally considered "a small niche market"[1] and perceived as suitable for "specialized field applications" such as "the military, the Internal Revenue Service, accountants and sales representatives"[1][2], battery-powered portables had just 2% worldwide market share in 1986[3]. But today, there are already more laptops than desktops in the enterprise[4] and, according to a forecast by Intel, more laptops than desktops will be sold in the general PC market as soon as 2009History
As the personal computer began to become feasible in the early 1970s, the idea of a portable personal computer followed; in particular, a "personal, portable information manipulator" was envisioned by Alan Kay at Xerox PARC in 1968[6] and described in his 1972 paper as the "Dynabook"[7].
The first commercially available portable computer appeared 9 years later, in 1981. The Osborne 1 weighed 23.5 pounds (10.7 kg). It had no battery, a tiny 5" CRT screen and dual 5¼" single-density floppy drives. In the same year the first laptop-sized portable computer, the Epson HX-20, was announced[8]. The Epson had a LCD screen, a rechargeable battery and a calculator-size printer in a 1.6 kg (4 pounds) enclosure.
The first notebook using the clamshell design (which is utilized today by almost all laptops) appeared in 1982: the $8150 GRiD Compass 1100 was purchased by NASA and the military among others. The Gavilan SC, released in 1983, was the first notebook that was marketed using the term "laptop".
From 1983 onwards:
- Several new input methods were introduced: the touchpad (Gavilan SC, 1983), the pointing stick (IBM ThinkPad 700, 1992) and handwriting recognition (Linus Write-Top[9], 1987).
- CPUs became designed specifically for laptops (Intel i386SL, 1990), targeting low power consumption, and were augmented with dynamic power management features (Intel SpeedStep and AMD PowerNow!).
- Displays reached VGA resolution by 1988 (Compaq SLT 286) and 256-color screens by 1993 (PowerBook 165c), progressing quickly to millions of colors and high resolutions.
- High-capacity hard drives and optical storage (CD-ROM followed by DVD) became available in laptops soon after their introduction to the desktops.
Early laptops often had proprietary and incompatible architectures, operating systems and bundled applications.
[edit] Classification
The general terms "laptop" or "notebook" can be used to refer to a number of classes of small portable computers:[10][11]
| By purpose and (approximately) by screen size:
| By features: |
[edit] 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 numerous ports, and have a 17" or larger display. Because of their bulk, they are not as portable as other laptops and their operation time on batteries is typically shorter.[11]
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.[12]
The names "Media Center Laptops" and "Gaming Laptops" are also used to describe this class of notebooks.[10]
[edit] 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)[10]; the battery life can exceed 10 hours[13] 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.
[edit] Netbook
A netbook is a small laptop designed for portability and low price, with a performance inferior to that of a standard notebook yet adequate for surfing on the Internet and basic word processing. Netbooks use 10" and smaller screens, weigh 0.6 to 1.2 kg (1.5 to 3 pounds), and are generally powered by a CPU from one of the low-cost families with a high performance-to-power ratio such as Intel Atom, Celeron ULV, or VIA C7 processors.[14]
Netbooks use general-purpose operating systems such as Linux or Windows XP. Some models use small-capacity (4 to 40 Gb) SSD drives instead of the usual HDDs to save weight and battery power.
[edit] Components
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 have worse performance than desktop parts of comparable price. Furthermore, the design bounds on power, size, and cooling of laptops limit the maximum performance of laptop parts compared to that of desktop components. [15]
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 or proprietary expansion slots. Several other functions (storage controllers, networking, sound card and external ports) are implemented on the motherboard.[16]
- Central processing unit (CPU) - Laptop CPUs have advanced power-saving features and produce less heat than desktop processors, but are not as powerful.[17] 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).
- Memory (RAM) - SO-DIMM memory modules that are usually found in laptops are about half the size of desktop DIMMs.[16] 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.Laptops typically use SODIMMs, as shown here.
- 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 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. [18]
- Power supply - laptops are 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. Batteries' performance gradually decreases with time, leading to an eventual replacement in one to five 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.
- Video display controller - on standard laptops 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[19]. 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.[20]
- Display - Most modern laptops feature 12 inch (30 cm) or larger color active matrix displays with resolutions of 1024×768 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[21] can be found on 19" widescreen desktop monitors).
- Removable media drives - a DVD/CD reader/writer drive is standard. CD drives are becoming rare, while Blu-Ray is not yet common on notebooks[22]. Many ultraportables and netbooks either move the removable media drive into the docking station or exclude it altogether.
- Internal storage - Hard disks are physically smaller—2.5 inch (60 mm) or 1.8 inch (46 mm) —compared to desktop 3.5 inch (90 mm) drives. Some new laptops (usually ultraportables) employ more expensive, but faster, lighter and power-efficient Flash memory-based SSDs instead. Currently, 160 to 250 Gb sizes are common for laptop hard disks (64 to 128 Gb for SSDs).2.5" hard disk drive
- 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. External keyboard and 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.
[edit] 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, the "port replicator" has gained popularity. The port replicator was a cheaper, often passive device that simply mated to the connectors on the back of the notebook and allowed the user to quickly connect his laptop so that his monitor, keyboard, printer and other devices were instantly attached. As higher speed ports such as USB and Firewire became common, the connection of a port replicator to a laptop was accomplished by a small cable connected to one of the USB or FireWire ports on the notebook. Wireless Port Replicators are available as well.
A recent variant of the port replicator is the combined power/display/USB hub cable found in the new Apple Cinema Display[23].
[edit] 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.[18] Subtle incompatibilities and variations in dimensions, however, are not uncommon.[24] Depending on the manufacturer and model, a laptop may range from having several standard, easily customizable and upgradeable parts to a proprietary design that can't 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, 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.
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.
[edit] Advantages
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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, less energy consumption and heat production.
[edit] Disadvantages
[edit] Parts standardization and compatibility issues
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Current compatibility problems in the laptop trade are reflective of the early era of personal computer hardware, when there were many different manufacturers, each and every one of them having their own connectivity and mounting systems and incompatibility was the norm. While there are accepted world standards of form factors for all the peripherals and add-in PC cards used in the desktop computers, there are still no firm worldwide standards relating to today's laptops' internal form factors, such as supply of electric voltage, motherboard layouts, internal adapters used in connecting the optical drive, LCD cable, keyboard and floppy drive to the main board. Most affected by this are users uneducated in the relevant fields, especially if they attempt to connect their laptops with incompatible hardware or power adapters.
Some hard drives and memory are commodity items and are interchangeable. However, other parts such as motherboards, keyboards, and batteries are proprietary in design and are only interchangeable within a manufactures brand and/or model line.
A significant point to note is that the vast majority of laptops on the market are manufactured by a small handful of Original Design Manufacturers (ODM).[25] The ODM matters more than the Original Equipment Manufacturer (OEM). Major relationships include:
- Quanta sell to (among others) HP/Compaq, Dell, Toshiba, Sony, Fujitsu, Acer, NEC, Gateway and Lenovo/IBM - note that Quanta is currently (as of August, 2007) the largest manufacturer of notebook computers in the world.
- Compal sells to Toshiba, HP/Compaq, Acer, and Dell.
- Wistron (former manufacturing & design division of Acer) sells to HP/Compaq, Dell, IBM, NEC, Acer, and Lenovo/IBM.
- Flextronics (former Arima Computer Corporation notebook division) sells to HP/Compaq, NEC, and Dell.
- ECS sells to IBM, Fujitsu, and Dell.
- Asus sells to Apple (iBook), Sony, and Samsung.
- Inventec sells to HP/Compaq, Toshiba, and BenQ.
- Uniwill sells to Lenovo/IBM and Fujitsu.
[edit] Durability problems
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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 heat sink 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.
[edit] Rugged laptops
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Some manufacturers have mitigated some of these problems by selling "ruggedized" laptops. These often have a rubber 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.)
[edit] 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.[26]
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
[edit] Performance
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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.
As computer hardware miniaturization develops, 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 Inc., 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, while maintaining long battery life.
[edit] Health problems
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.[27] 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.[28]
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.
[edit] 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.[29] 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.
[edit] Related devices
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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:
- Transportable, also called portable computers
- Computers which can easily be moved from place to place, but cannot be used while in transit, usually because they require AC power. The most famous example is the Osborne 1. A transportable, like a laptop, can run desktop software; but it does not support mobile computing.
- Tablets
- Computers shaped like slates or (paper) notebooks featuring touchscreen interfaces and a stylus, plus handwriting recognition software. As of 2007, the most common subcategory is the Tablet PC, which is essentially a laptop with a touchscreen. Some tablets have no keyboard, while others called "convertibles" have a screen that can be rotated 180 degrees and folded on top of the keyboard. Tablets may have limited functionality and not be best suited for applications requiring a physical keyboard for typing, but are otherwise capable of carrying out most tasks that an ordinary laptop would be able to perform.
- Internet tablets
- Internet appliances in tablet form. An internet tablet supports mobile computing. Internet tablets usually use Linux and they are able to run some applications, but they cannot replace a general purpose computer. Internet tablets typically feature an MP3 and video player, web browser, chat application, and picture viewer.
- Personal digital assistants (PDAs)
- Small computers, usually pocket-sized, usually with limited functionality. A PDA supports mobile computing, but almost never runs any desktop software.
- Handheld computers
- A high-end PDA or small tablet.
- Smart phone
- A hand held or PDA with an integrated cellphone.
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.
[edit] Major brands and manufacturers
 | It has been suggested that this section be split into a new article entitled List of laptop manufacturers. (Discuss) |
| Major brands
| Other brands
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