Tech Terms | Abbreviations A–Z
A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building. By contrast, a wide area network (WAN) not only covers a larger geographic distance, but also generally involves leased telecommunication circuits.
A laptop computer or notebook computer, also known as a laptop or notebook for short, is a small, portable personal computer (PC). Laptops typically have a clamshell form factor with a flat panel screen (usually 11–17 in or 280–430 mm in diagonal size) on the inside of the upper lid and an alphanumeric keyboard and pointing device (such as a trackpad and/or trackpoint) on the inside of the lower lid, although 2-in-1 PCs with a detachable keyboard are often marketed as laptops or as having a "laptop mode". Most of the computer's internal hardware is fitted inside the lower lid enclosure under the keyboard, although many laptops have a built-in webcam at the top of the screen and some modern ones even feature a touch-screen display. In most cases, unlike tablet computers which run on mobile operating systems, laptops tend to run on desktop operating systems which have been traditionally associated with desktop computers.
Laptops run on both an AC power supply and a rechargeable battery pack and can be folded shut for convenient storage and transportation, making them suitable for mobile use. Today, laptops are used in a variety of settings, such as at work (especially on business trips), in education, for playing games, web browsing, for personal multimedia, and for general home computer use.
The names "laptop" and "notebook" refer to the fact that the computer can be practically placed on (or on top of) the user's lap and can be used similarly to a notebook. As of 2022, in American English, the terms "laptop" and "notebook" are used interchangeably; in other dialects of English, one or the other may be preferred. Although the term "notebook" originally referred to a specific size of laptop (originally smaller and lighter than mainstream laptops of the time), the term has come to mean the same thing and no longer refers to any specific size.
Laptops combine many of the input/output components and capabilities of a desktop computer into a single unit, including a display screen, small speakers, a keyboard, and a pointing device (such as a touch pad or pointing stick). Most modern laptops include a built-in webcam and microphone, and many also have a touchscreen. Laptops can be powered by an internal battery or an external power supply by using an AC adapter. Hardware specifications may vary significantly between different types, models, and price points.
Design elements, form factors, and construction can also vary significantly between models depending on the intended use. Examples of specialized models of laptops include rugged notebooks for use in construction or military applications, as well as low-production-cost laptops such as those from the One Laptop per Child (OLPC) organization, which incorporate features like solar charging and semi-flexible components not found on most laptop computers. Portable computers, which later developed into modern laptops, were originally considered to be a small niche market, mostly for specialized field applications, such as in the military, for accountants, or traveling sales representatives. As portable computers evolved into modern laptops, they became widely used for a variety of purposes.
A lithium-ion or Li-ion battery is a type of rechargeable battery that uses the reversible intercalation of Li+ ions into electronically conducting solids to store energy. In comparison with other commercial rechargeable batteries, Li-ion batteries are characterized by higher specific energy, higher energy density, higher energy efficiency, a longer cycle life, and a longer calendar life. Also noteworthy is a dramatic improvement in lithium-ion battery properties after their market introduction in 1991: within the next 30 years, their volumetric energy density increased threefold while their cost dropped tenfold.
The invention and commercialization of Li-ion batteries may have had one of the greatest impacts of all technologies in human history, as recognized by the 2019 Nobel Prize in Chemistry. More specifically, Li-ion batteries enabled portable consumer electronics, laptop computers, cellular phones, and electric cars, or what has been called the e-mobility revolution. It also sees significant use for grid-scale energy storage as well as military and aerospace applications.
Lithium-ion cells can be manufactured to optimize energy or power density. Handheld electronics mostly use lithium polymer batteries (with a polymer gel as an electrolyte), a lithium cobalt oxide (LiCoO2) cathode material, and a graphite anode, which together offer high energy density. Lithium iron phosphate (LiFePO4), lithium manganese oxide (LiMn2O4 spinel, or Li2MnO3-based lithium-rich layered materials, LMR-NMC), and lithium nickel manganese cobalt oxide (LiNiMnCoO2 or NMC) may offer longer life and a higher discharge rate. NMC and its derivatives are widely used in the electrification of transport, one of the main technologies (combined with renewable energy) for reducing greenhouse gas emissions from vehicles.
M. Stanley Whittingham conceived intercalation electrodes in the 1970s and created the first rechargeable lithium-ion battery, based on a titanium disulfide cathode and a lithium-aluminum anode, although it suffered from safety problems and was never commercialized. John Goodenough expanded on this work in 1980 by using lithium cobalt oxide as a cathode. The first prototype of the modern Li-ion battery, which uses a carbonaceous anode rather than lithium metal, was developed by Akira Yoshino in 1985 and commercialized by a Sony and Asahi Kasei team led by Yoshio Nishi in 1991. M. Stanley Whittingham, John Goodenough and Akira Yoshino were awarded the 2019 Nobel Prize in Chemistry for their contributions to the development of lithium-ion batteries.
Lithium-ion batteries can be a safety hazard if not properly engineered and manufactured because they have flammable electrolytes that, if damaged or incorrectly charged, can lead to explosions and fires. Much progress has been made in the development and manufacturing of safe lithium-ion batteries. Lithium-ion solid-state batteries are being developed to eliminate the flammable electrolyte. Improperly recycled batteries can create toxic waste, especially from toxic metals, and are at risk of fire. Moreover, both lithium and other key strategic minerals used in batteries have significant issues at extraction, with lithium being water intensive in often arid regions and other minerals often being conflict minerals such as cobalt. Both environmental issues have encouraged some researchers to improve mineral efficiency and find alternatives such as iron-air batteries.
Research areas for lithium-ion batteries include extending lifetime, increasing energy density, improving safety, reducing cost, and increasing charging speed, among others. Research has been under way in the area of non-flammable electrolytes as a pathway to increased safety based on the flammability and volatility of the organic solvents used in the typical electrolyte. Strategies include aqueous lithium-ion batteries, ceramic solid electrolytes, polymer electrolytes, ionic liquids, and heavily fluorinated systems.
In telecommunications, Long-Term Evolution (LTE) is a standard for wireless broadband communication for mobile devices and data terminals, based on the GSM/EDGE and UMTS/HSPA technologies. It increases the capacity and speed using a different radio interface together with core network improvements. LTE is the upgrade path for carriers with both GSM/UMTS networks and CDMA2000 networks. The different LTE frequencies and bands used in different countries mean that only multi-band phones are able to use LTE in all countries where it is supported.
The standard is developed by the 3GPP (3rd Generation Partnership Project) and is specified in its Release 8 document series, with minor enhancements described in Release 9. LTE is sometimes known as 3.95G and has been marketed both as "4G LTE" and as "Advanced 4G", but it does not meet the technical criteria of a 4G wireless service, as specified in the 3GPP Release 8 and 9 document series for LTE Advanced. The requirements were originally set forth by the ITU-R organisation in the IMT Advanced specification. However, due to marketing pressures and the significant advancements that WiMAX, Evolved High Speed Packet Access, and LTE bring to the original 3G technologies, ITU later decided that LTE together with the aforementioned technologies can be called 4G technologies. The LTE Advanced standard formally satisfies the ITU-R requirements to be considered IMT-Advanced. To differentiate LTE Advanced and WiMAX-Advanced from current 4G technologies, ITU has defined them as "True 4G".