Blog

A microwave oven or simply microwave is an electric oven that heats and cooks food by exposing it to electromagnetic radiation in the microwave frequency range.^[1] This induces polar molecules in the food to rotate and produce thermal energy (heat) in a process known as dielectric heating. Microwave ovens heat foods quickly and efficiently because the heating effect is fairly uniform in the outer 25–38 mm (1–1.5 inches) of a homogeneous, high-water-content food item.

The development of the cavity magnetron in the United Kingdom made possible the production of electromagnetic waves of a small enough wavelength (microwaves) to efficiently heat up water molecules. American electrical engineer Percy Spencer is generally credited with developing and patenting the world’s first commercial microwave oven, the “Radarange”, which was first sold in 1947. He based it on British radar technology which had been developed before and during World War II.^{[citation needed]}

Raytheon later licensed its patents for a home-use microwave oven that was introduced by Tappan in 1955, but it was still too large and expensive for general home use. Sharp Corporation introduced the first microwave oven with a turntable between 1964 and 1966. The countertop microwave oven was introduced in 1967 by the Amana Corporation. After microwave ovens became affordable for residential use in the late 1970s, their use spread into commercial and residential kitchens around the world, and prices fell rapidly during the 1980s. In addition to cooking food, microwave ovens are used for heating in many industrial processes.^{[citation needed]}

Microwave ovens are a common kitchen appliance and are popular for reheating previously cooked foods and cooking a variety of foods. They rapidly heat foods which can easily burn or turn lumpy if cooked in conventional pans, such as hot butter, fats, chocolate, or porridge. Microwave ovens usually do not directly brown or caramelize food, since they rarely attain the necessary temperature to produce Maillard reactions. Exceptions occur in cases where the oven is used to heat frying-oil and other oily items (such as bacon), which attain far higher temperatures than that of boiling water.^{[citation needed]}

Microwave ovens have a limited role in professional cooking,^[2] because the boiling-range temperatures of a microwave oven do not produce the flavorful chemical reactions that frying, browning, or baking at a higher temperature produces. However, such high-heat sources can be added to microwave ovens in the form of a convection microwave oven.^[3]

History

Early developments

Demonstration by Westinghouse of cooking sandwiches with a 60 MHz shortwave radio transmitter at the 1933 Chicago World’s Fair

The exploitation of high-frequency radio waves for heating substances was made possible by the development of vacuum tube radio transmitters around 1920. By 1930 the application of short waves to heat human tissue had developed into the medical therapy of diathermy. At the 1933 Chicago World’s Fair, Westinghouse demonstrated the cooking of foods between two metal plates attached to a 10 kW, 60 MHz shortwave transmitter.^[4] The Westinghouse team, led by I. F. Mouromtseff, found that foods like steaks and potatoes could be cooked in minutes.^[5]

The 1937 United States patent application by Bell Laboratories states:^[6]

This invention relates to heating systems for dielectric materials and the object of the invention is to heat such materials uniformly and substantially simultaneously throughout their mass. … It has been proposed therefore to heat such materials simultaneously throughout their mass by means of the dielectric loss produced in them when they are subjected to a high voltage, high frequency field.

However, lower-frequency dielectric heating, as described in the aforementioned patent, is (like induction heating) an electromagnetic heating effect, the result of the so-called near-field effects that exist in an electromagnetic cavity that is small compared with the wavelength of the electromagnetic field. This patent proposed radio frequency heating, at 10 to 20 megahertz (wavelength 30 to 15 meters, respectively).^[7] Heating from microwaves that have a wavelength that is small relative to the cavity (as in a modern microwave oven) is due to “far-field” effects that are due to classical electromagnetic radiation that describes freely propagating light and microwaves suitably far from their source. Nevertheless, the primary heating effect of all types of electromagnetic fields at both radio and microwave frequencies occurs via the dielectric heating effect, as polarized molecules are affected by a rapidly alternating electric field.

Cavity magnetron

Main article: Cavity magnetron

The invention of the cavity magnetron made possible the production of electromagnetic waves of a small enough wavelength (microwaves). The cavity magnetron was a crucial component in the development of short wavelength radar during World War II.^[8] In 1937–1940, a multi-cavity magnetron was built by British physicist Sir John Turton Randall, FRSE and coworkers, for the British and American military radar installations in World War II.^[9] A higher-powered microwave generator that worked at shorter wavelengths was needed, and in 1940, at the University of Birmingham in England, Randall and Harry Boot produced a working prototype.^[10] They invented a valve that could produce pulses of microwave radio energy at a wavelength of 10 cm, an unprecedented discovery.^[9]

Sir Henry Tizard traveled to the US in late September 1940 to offer Britain’s most valuable technical secrets including the cavity magnetron in exchange for US financial and industrial support (see Tizard Mission).^[9] An early 6 kW version, built in England by the General Electric Company Research Laboratories, Wembley, London, was given to the U.S. government in September 1940. The cavity magnetron was later described by American historian James Phinney Baxter III as “[t]he most valuable cargo ever brought to our shores”.^[11] Contracts were awarded to Raytheon and other companies for the mass production of the cavity magnetron.

Discovery

In 1945, the heating effect of a high-power microwave beam was independently and accidentally discovered by Percy Spencer, an American self-taught engineer from Howland, Maine. Employed by Raytheon at the time, he noticed that microwaves from an active radar set he was working on started to melt a candy bar he had in his pocket. The first food deliberately cooked by Spencer was popcorn, and the second was an egg, which exploded in the face of one of the experimenters.^[12][13][14]

To verify his finding, Spencer created a high-density electromagnetic field by feeding microwave power from a magnetron into a metal box from which it had no way to escape. When food was placed in the box with the microwave energy, the temperature of the food rose rapidly. On 8 October 1945, Raytheon filed a United States patent application for Spencer’s microwave cooking process, and an oven that heated food using microwave energy from a magnetron was soon placed in a Boston restaurant for testing.^[15]

Commercial availability

In 1947, Raytheon built the “Radarange”, the first commercially available microwave oven.^[16] It was almost 1.8 metres (5 ft 11 in) tall, weighed 340 kilograms (750 lb) and cost about US$5,000 ($70,000 in 2024 dollars) each. It consumed 3 kilowatts, about three times as much as today’s microwave ovens, and was water-cooled. The name was the winning entry in an employee contest.^[17] An early Radarange was installed (and remains) in the galley of the nuclear-powered passenger/cargo ship NS Savannah. An early commercial model introduced in 1954 consumed 1.6 kilowatts and sold for US$2,000 to US$3,000 ($23,000 to $35,000 in 2024 dollars). Raytheon licensed its technology to the Tappan Stove company of Mansfield, Ohio in 1952.^[18] Under contract to Whirlpool, Westinghouse, and other major appliance manufacturers looking to add matching microwave ovens to their conventional oven line, Tappan produced several variations of their built-in model from roughly 1955 to 1960. Due to maintenance (some units were water-cooled), in-built requirement, and cost—US$1,295 ($15,000 in 2024 dollars)—sales were limited.^[19]

Japan’s Sharp Corporation began manufacturing microwave ovens in 1961. Between 1964 and 1966, Sharp introduced the first microwave oven with a turntable, an alternative means to promote more even heating of food.^[20] In 1965, Raytheon, looking to expand their Radarange technology into the home market, acquired Amana to provide more manufacturing capability. In 1967, they introduced the first popular home model, the countertop Radarange, at a price of US$495 ($5,000 in 2024 dollars). Unlike the Sharp models, a motor driven mode stirrer in the top of the oven cavity rotated allowing the food to remain stationary.

In the 1960s,^[specify] Litton bought Studebaker‘s Franklin Manufacturing assets, which had been manufacturing magnetrons and building and selling microwave ovens similar to the Radarange. Litton developed a new configuration of the microwave oven: the short, wide shape that is now common. The magnetron feed was also unique. This resulted in an oven that could survive a no-load condition: an empty microwave oven where there is nothing to absorb the microwaves. The new oven was shown at a trade show in Chicago,^{[citation needed]} and helped begin a rapid growth of the market for home microwave ovens. Sales volume of 40,000 units for the U.S. industry in 1970 grew to one million by 1975. Market penetration was even faster in Japan, due to a less expensive re-engineered magnetron. Several other companies joined in the market, and for a time most systems were built by defence contractors, who were most familiar with the magnetron. Litton was particularly well known in the restaurant business.^{[citation needed]}

Residential use

While uncommon today, combination microwave-ranges were offered by major appliance manufacturers through much of the 1970s as a natural progression of the technology. Both Tappan and General Electric offered units that appeared to be conventional stove top/oven ranges, but included microwave capability in the conventional oven cavity. Such ranges were attractive to consumers since both microwave energy and conventional heating elements could be used simultaneously to speed cooking, and there was no loss of countertop space. The proposition was also attractive to manufacturers as the additional component cost could better be absorbed compared with countertop units where pricing was increasingly market-sensitive.^{[citation needed]}

By 1972, Litton (Litton Atherton Division, Minneapolis) introduced two new microwave ovens, priced at $349 and $399, to tap into the market estimated at $750 million by 1976, according to Robert I Bruder, president of the division.^[21] While prices remained high, new features continued to be added to home models. Amana introduced automatic defrost in 1974 on their RR-4D model, and was the first to offer a microprocessor controlled digital control panel in 1975 with their RR-6 model.

The late 1970s saw an explosion of low-cost countertop models from many major manufacturers.^{[citation needed]}

Formerly found only in large industrial applications, microwave ovens increasingly became a standard fixture of residential kitchens in developed countries. By 1986, roughly 25% of households in the U.S. owned a microwave oven, up from only about 1% in 1971;^[22] the U.S. Bureau of Labor Statistics reported that over 90% of American households owned a microwave oven in 1997.^[22][23] In Australia, a 2008 market research study found that 95% of kitchens contained a microwave oven and that 83% of them were used daily.^[24] In Canada, fewer than 5% of households had a microwave oven in 1979, but more than 88% of households owned one by 1998.^[25] In France, 40% of households owned a microwave oven in 1994, but that number had increased to 65% by 2004.^[26]

Adoption has been slower in less-developed countries, as households with disposable income concentrate on more important household appliances like refrigerators and ovens. In India, for example, only about 5% of households owned a microwave oven in 2013, well behind refrigerators at 31% ownership.^[27] However, microwave ovens are gaining popularity. In Russia, for example, the number of households with a microwave oven grew from almost 24% in 2002 to almost 40% in 2008.^[28] Almost twice as many households in South Africa owned microwave ovens in 2008 (38.7%) as in 2002 (19.8%).^[28] Microwave oven ownership in Vietnam in 2008 was at 16% of households, versus 30% ownership of refrigerators; this rate was up significantly from 6.7% microwave oven ownership in 2002, with 14% ownership for refrigerators that year.^[28]

Consumer household microwave ovens usually come with a cooking power of between 600 and 1200 watts. Microwave cooking power, also referred to as output wattage, is lower than its input wattage, which is the manufacturer’s listed power rating.^{[citation needed]}

The size of household microwave ovens can vary, but usually have an internal volume of around 20 liters (1,200 cu in; 0.71 cu ft), and external dimensions of approximately 45–60 cm (1 ft 6 in – 2 ft 0 in) wide, 35–40 cm (1 ft 2 in – 1 ft 4 in) deep and 25–35 cm (9.8 in – 1 ft 1.8 in) tall.^[29] Countertop microwaves vary in weight 23 – 45 lbs.^[30]

Microwaves can be turntable or flatbed. Turntable ovens include a glass plate or tray. Flatbed ones do not include a plate, so they have a flat and wider cavity.^[31][32][33]

By position and type, US DOE classifies them as (1) countertop or (2) over the range and built-in (wall oven for a cabinet or a drawer model).^[31]

A traditional microwave only has two power output levels, fully on and fully off. Intermediate heat settings are achieved using duty-cycle modulation and switch between full power and off every few seconds, with more time on for higher settings.^{[citation needed]}

An inverter type, however, can sustain lower temperatures for a lengthy duration without having to switch itself off and on repeatedly. Apart from offering superior cooking ability, these microwaves are generally more energy-efficient.^[34][33][35]

As of 2020, the majority of countertop microwave ovens (regardless of brand) sold in the United States were manufactured by the Midea Group.^[36]

Categories

Domestic microwave ovens are typically marked with the microwave-safe symbol, next to the device’s approximate IEC 60705 output power rating, in watts (typically either: 600W, 700W, 800W, 900W, 1000W), and a voluntary Heating Category (A-E).^[37]

Principles

Further information: Dielectric heating

Duration: 31 seconds.0:31Simulation of the electric field inside a microwave oven for the first 8 ns of operation

A microwave oven heats food by passing microwave radiation through it. Microwaves are a form of non-ionizing electromagnetic radiation with a frequency in the so-called microwave region (300 MHz to 300 GHz). Microwave ovens use frequencies in one of the ISM (industrial, scientific, medical) bands, which are otherwise used for communication amongst devices that do not need a license to operate, so they do not interfere with other vital radio services.

It is a common misconception that microwave ovens heat food by operating at a special resonance of water molecules in the food.^{[citation needed]} Instead, microwave ovens heat by causing molecules to spin under the influence of a constantly changing electric field, usually in the microwave frequencies range, and a higher wattage power of the microwave oven results in faster cooking times.^{[citation needed]} Typically, consumer ovens work around a nominal 2.45 gigahertz (GHz) – a wavelength of 12.2 centimetres (4.80 in) in the 2.4 GHz to 2.5 GHz ISM band – while large industrial / commercial ovens often use 915 megahertz (MHz) – 32.8 centimetres (12.9 in).^[38] Among other differences, the longer wavelength of a commercial microwave oven allows the initial heating effects to begin deeper within the food or liquid, and therefore become evenly spread within its bulk sooner, as well as raising the temperature deep within the food more quickly.^[39]

A microwave oven takes advantage of the electric dipole structure of water molecules, fats, and many other substances in the food, using a process known as dielectric heating. These molecules have a partial positive charge at one end and a partial negative charge at the other. In an alternating electric field, they will constantly spin around as they continually try to align themselves with the electric field. This can happen over a wide range of frequencies.^[40][41][42] The electric field’s energy is absorbed by the dipole molecules as rotational energy. Then they hit non-dipole molecules, making them move faster as well. This energy is shared deeper into the substance as molecular rotation and translational movement occurs, signifying an increase in the temperature of the food. Once the electrical field’s energy is initially absorbed, heat will gradually spread through the object similarly to any other heat transfer by contact with a hotter body.^[43]

Defrosting

Microwave heating is more efficient on liquid water than on frozen water, where the movement of molecules is more restricted. Defrosting is done at a low power setting, allowing time for conduction to carry heat to still frozen parts of food. Dielectric heating of liquid water is also temperature-dependent: At 0 °C, dielectric loss is greatest at a field frequency of about 10 GHz, and for higher water temperatures at higher field frequencies.^[44]

Fats and sugar

Sugars and triglycerides (fats and oils) absorb microwaves due to the dipole moments of their hydroxyl groups or ester groups. Microwave heating is less efficient on fats and sugars than on water because they have a smaller molecular dipole moment.^[a]

Although fats and sugar typically absorb energy less efficiently than water, paradoxically their temperatures rise faster and higher than water when cooking: Fats and oils require less energy delivered per gram of material to raise their temperature by 1 °C than does water (they have lower specific heat capacity) and they begin cooling off by “boiling” only after reaching a higher temperature than water (the temperature they require to vaporize is higher), so inside microwave ovens they normally reach higher temperatures – sometimes much higher.^[44] This can induce temperatures in oil or fatty foods like bacon far above the boiling point of water, and high enough to induce some browning reactions, much in the manner of conventional broiling (UK: grilling), braising, or deep fat frying.

The effect is most often noticed by consumers from unexpected damage to plastic containers when microwaving foods high in sugar, starch, or fat generates higher temperatures.^{[citation needed]} Foods high in water content and with little oil rarely exceed the boiling temperature of water and do not damage plastic.^{[citation needed]}

Cookware

Cookware must be transparent to microwaves. Conductive cookware, such as metal pots, reflects microwaves, and prevents the microwaves from reaching the food.^{[citation needed]} Cookware made of materials with high electrical permittivity will absorb microwaves, resulting in the cookware heating rather than the food. Cookware made of melamine resin is a common type of cookware that will heat in a microwave oven, reducing the effectiveness of the microwave oven and creating a hazard from burns or shattered cookware.^{[citation needed]}

Thermal runaway

Microwave heating can cause localized thermal runaways in some materials with low thermal conductivity which also have dielectric constants that increase with temperature. An example is glass, which can exhibit thermal runaway in a microwave oven to the point of melting if preheated. Additionally, microwaves can melt certain types of rocks, producing small quantities of molten rock. Some ceramics can also be melted, and may even become clear upon cooling. Thermal runaway is more typical of electrically conductive liquids such as salty water.^[45]

Penetration

Another misconception is that microwave ovens cook food “from the inside out”, meaning from the center of the entire mass of food outwards.^{[citation needed]} This idea arises from heating behavior seen if an absorbent layer of water lies beneath a less absorbent drier layer at the surface of a food; in this case, the deposition of heat energy inside a food can exceed that on its surface.^{[citation needed]} This can also occur if the inner layer has a lower heat capacity than the outer layer causing it to reach a higher temperature, or even if the inner layer is more thermally conductive than the outer layer making it feel hotter despite having a lower temperature. In most cases, however, with uniformly structured or reasonably homogeneous food item, microwaves are absorbed in the outer layers of the item at a similar level to that of the inner layers.^{[citation needed]}

Depending on water content, the depth of initial heat deposition may be several centimetres or more with microwave ovens, in contrast with broiling / grilling (infrared) or convection heating methods which thinly deposit heat at the food surface. Penetration depth of microwaves depends on food composition and the frequency, with lower microwave frequencies (longer wavelengths) penetrating deeper.^[39]

Energy consumption

In use, microwave ovens can be as low as 50% efficient at converting electricity into microwaves,^[46] but energy-efficient models can exceed 64% efficiency.^[47] Stovetop cooking is 40–90% efficient, depending on the type of appliance used.^[48]

Because they are used fairly infrequently, the average residential microwave oven consumes only 72 kWh per year.^[49] Globally, microwave ovens used an estimated 77 TWh per year in 2018, or 0.3% of global electricity generation.^[50]

A 2000 study by Lawrence Berkeley National Laboratory found that the average microwave drew almost 3 watts of standby power when not being used,^[51] which would total approximately 26 kWh per year. New efficiency standards imposed in 2016 by the United States Department of Energy require less than 1 watt, or approximately 9 kWh per year, of standby power for most types of microwave ovens.^[52]

Components

A microwave oven generally consists of:

• a high-voltage DC power source, either:
  • a large high voltage transformer with a voltage doubler (a high-voltage capacitor and a diode)
  • an electronic power converter usually based around an inverter.
• a cavity magnetron, which converts the high-voltage DC electric energy to microwave radiation
• a magnetron control circuit (usually with a microcontroller)
• a short waveguide (to couple microwave power from the magnetron into the cooking chamber)
• a turntable and/or metal wave guide stirring fan
• a control panel

In most ovens, the magnetron is driven by a linear transformer which can only feasibly be switched completely on or off. (One variant of the GE Spacemaker had two taps on the transformer primary, for high and low power modes.) Usually choice of power level does not affect intensity of the microwave radiation; instead, the magnetron is cycled on and off every few seconds, thus altering the large scale duty cycle. Newer models use inverter power supplies that use pulse-width modulation to provide effectively continuous heating at reduced power settings, so that foods are heated more evenly at a given power level and can be heated more quickly without being damaged by uneven heating.^{[53][34][33][35]}

The microwave frequencies used in microwave ovens are chosen based on regulatory and cost constraints. The first is that they should be in one of the industrial, scientific, and medical (ISM) frequency bands set aside for unlicensed purposes. For household purposes, 2.45 GHz has the advantage over 915 MHz in that 915 MHz is only an ISM band in some countries (ITU Region 2) while 2.45 GHz is available worldwide.^{[citation needed]} Three additional ISM bands exist in the microwave frequencies, but are not used for microwave cooking. Two of them are centered on 5.8 GHz and 24.125 GHz, but are not used for microwave cooking because of the very high cost of power generation at these frequencies.^{[citation needed]} The third, centered on 433.92 MHz, is a narrow band that would require expensive equipment to generate sufficient power without creating interference outside the band, and is only available in some countries.^{[citation needed]}

The cooking chamber is similar to a Faraday cage to prevent the waves from coming out of the oven. Even though there is no continuous metal-to-metal contact around the rim of the door, choke connections on the door edges act like metal-to-metal contact, at the frequency of the microwaves, to prevent leakage. The oven door usually has a window for easy viewing, with a layer of conductive mesh some distance from the outer panel to maintain the shielding. Because the size of the perforations in the mesh is much less than the microwaves’ wavelength (12.2 cm for the usual 2.45 GHz), microwave radiation cannot pass through the door, while visible light (with its much shorter wavelength) can.^[54]

Control panel

Modern microwave ovens use either an analog dial-type timer or a digital control panel for operation. Control panels feature an LED, LCD or vacuum fluorescent display, buttons for entering the cook time and a power level selection feature. A defrost option is typically offered, as either a power level or a separate function. Some models include pre-programmed settings for different food types, typically taking weight as input. In the 1990s, brands such as Panasonic and GE began offering models with a scrolling-text display showing cooking instructions.

Power settings are commonly implemented not by actually varying the power output, but by switching the emission of microwave energy off and on at intervals. The highest setting thus represents continuous power. Defrost might represent power for two seconds followed by no power for five seconds. To indicate cooking has completed, an audible warning such as a bell or a beeper is usually present, and/or “End” usually appears on the display of a digital microwave.

Microwave control panels are often considered awkward to use and are frequently employed as examples for user interface design.^[55]

Variants and accessories

A variant of the conventional microwave oven is the convection microwave oven. A convection microwave oven is a combination of a standard microwave oven and a convection oven. It allows food to be cooked quickly, yet come out browned or crisped, as from a convection oven. Convection microwave ovens are more expensive than conventional microwave ovens. Some convection microwave ovens—those with exposed heating elements—can produce smoke and burning odors as food spatter from earlier microwave-only use is burned off the heating elements. Some ovens use high speed air; these are known as impingement ovens and are designed to cook food quickly in restaurants, but cost more and consume more power.

In 2000, some manufacturers began offering high power quartz halogen bulbs to their convection microwave oven models,^[56] marketing them under names such as “Speedcook”, “Advantium“, “Lightwave” and “Optimawave” to emphasize their ability to cook food rapidly and with good browning. The bulbs heat the food’s surface with infrared (IR) radiation, browning surfaces as in a conventional oven. The food browns while also being heated by the microwave radiation and heated through conduction through contact with heated air. The IR energy which is delivered to the outer surface of food by the lamps is sufficient to initiate browning caramelization in foods primarily made up of carbohydrates and Maillard reactions in foods primarily made up of protein. These reactions in food produce a texture and taste similar to that typically expected of conventional oven cooking rather than the bland boiled and steamed taste that microwave-only cooking tends to create.

In order to aid browning, sometimes an accessory browning tray is used, usually composed of glass or porcelain. It makes food crisp by oxidizing the top layer until it turns brown.^[57] Ordinary plastic cookware is unsuitable for this purpose because it could melt.

Frozen dinners, pies, and microwave popcorn bags often contain a susceptor made from thin aluminium film in the packaging or included on a small paper tray. The metal film absorbs microwave energy efficiently and consequently becomes extremely hot and radiates in the infrared, concentrating the heating of oil for popcorn or even browning surfaces of frozen foods. Heating packages or trays containing susceptors are designed for a single use and are then discarded as waste.

Heating characteristics

Microwave ovens produce heat directly within the food, but despite the common misconception that microwaved food cooks from the inside out, 2.45 GHz microwaves can only penetrate approximately 1 centimeter (0.39 in) into most foods. The inside portions of thicker foods are mainly heated by heat conducted from the outer 1 centimeter (0.39 in).^[58][59]

Uneven heating in microwaved food can be partly due to the uneven distribution of microwave energy inside the oven, and partly due to the different rates of energy absorption in different parts of the food. The first problem is reduced by a stirrer, a type of fan that reflects microwave energy to different parts of the oven as it rotates, or by a turntable or carousel that turns the food; turntables, however, may still leave spots, such as the center of the oven, which receive uneven energy distribution.The location of dead spots and hot spots in a microwave oven can be mapped out by placing a damp piece of thermal paper in the oven: When the water-saturated paper is subjected to the microwave radiation it becomes hot enough to cause the dye to be darkened which can provide a visual representation of the microwaves. If multiple layers of paper are constructed in the oven with a sufficient distance between them a three-dimensional map can be created. Many store receipts are printed on thermal paper which allows this to be easily done at home.^[60]

The second problem is due to food composition and geometry, and must be addressed by the cook, by arranging the food so that it absorbs energy evenly, and periodically testing and shielding any parts of the food that overheat. In some materials with low thermal conductivity, where dielectric constant increases with temperature, microwave heating can cause localized thermal runaway. Under certain conditions, glass can exhibit thermal runaway in a microwave oven to the point of melting.^[61]

Due to this phenomenon, microwave ovens set at too-high power levels may even start to cook the edges of frozen food while the inside of the food remains frozen. Another case of uneven heating can be observed in baked goods containing berries. In these items, the berries absorb more energy than the drier surrounding bread and cannot dissipate the heat due to the low thermal conductivity of the bread. Often this results in overheating the berries relative to the rest of the food. “Defrost” oven settings either use low power levels or repeatedly turn the power off and on – intended to allow time for heat to be conducted within frozen foods from areas that absorb heat more readily to those which heat more slowly. In turntable-equipped ovens, more even heating can take place by placing food off-center on the turntable tray instead of exactly in the center, as this results in more even heating of the food throughout.^[62]

There are microwave ovens on the market that allow full-power defrosting. They do this by exploiting the properties of the electromagnetic radiation LSM modes. LSM full-power defrosting may actually achieve more even results than slow defrosting.^[63]

Microwave heating can be deliberately uneven by design. Some microwavable packages (notably pies) may include materials that contain ceramic or aluminium flakes, which are designed to absorb microwaves and heat up, which aids in baking or crust preparation by depositing more energy shallowly in these areas. The technical term for such a microwave-absorbing patch is a susceptor. Such ceramic patches affixed to cardboard are positioned next to the food, and are typically smokey blue or gray in colour, usually making them easily identifiable; the cardboard sleeves included with Hot Pockets, which have a silver surface on the inside, are a good example of such packaging. Microwavable cardboard packaging may also contain overhead ceramic patches which function in the same way.^[64]

Effects on food and nutrients

Any form of cooking diminishes overall nutrient content in food, particularly water-soluble vitamins common in vegetables, but the key variables are how much water is used in the cooking, how long the food is cooked, and at what temperature.^[65][66] Nutrients are primarily lost by leaching into cooking water, which tends to make microwave cooking effective, given the shorter cooking times it requires and that the water heated is in the food.^[67] Like other heating methods, microwaving converts vitamin B₁₂ from an active to inactive form; the amount of conversion depends on the temperature reached, as well as the cooking time. Boiled food reaches a maximum of 100 °C (212 °F) (the boiling point of water), whereas microwaved food can get internally hotter than this, leading to faster breakdown of vitamin B₁₂.^{[citation needed]} The higher rate of loss is partially offset by the shorter cooking times required.^[68]

Spinach retains nearly all its folate when cooked in a microwave oven; when boiled, it loses about 77%, leaching nutrients into the cooking water.^[67] Bacon cooked by microwave oven has significantly lower levels of nitrosamines than conventionally cooked bacon.^[66] Steamed vegetables tend to maintain more nutrients when microwaved than when cooked on a stovetop.^[66] Microwave blanching is 3–4 times more effective than boiled-water blanching for retaining of the water-soluble vitamins, folate, thiamin and riboflavin, with the exception of vitamin C, of which 29% is lost (compared with a 16% loss with boiled-water blanching).^[69]

Safety benefits and features

All microwave ovens use a timer to switch off the oven at the end of the cooking time.

Microwave ovens heat food without getting hot themselves. Taking a pot off a stove, unless it is an induction cooktop, leaves a potentially dangerous heating element or trivet that remains hot for some time. Likewise, when taking a casserole out of a conventional oven, one’s arms are exposed to the very hot walls of the oven. A microwave oven does not pose this problem.

Food and cookware taken out of a microwave oven are rarely much hotter than 100 °C (212 °F). Cookware used in a microwave oven is often much cooler than the food because the cookware is transparent to microwaves; the microwaves heat the food directly and the cookware is indirectly heated by the food. Food and cookware from a conventional oven, on the other hand, are the same temperature as the rest of the oven; a typical cooking temperature is 180 °C (356 °F). That means that conventional stoves and ovens can cause more serious burns.

The lower temperature of cooking (the boiling point of water) is a significant safety benefit compared with baking in the oven or frying, because it eliminates the formation of tars and char, which are carcinogenic.^[70] Microwave radiation also penetrates deeper than direct heat, so that the food is heated by its own internal water content. In contrast, direct heat can burn the surface while the inside is still cold. Pre-heating the food in a microwave oven before putting it into the grill or pan reduces the time needed to heat up the food and reduces the formation of carcinogenic char. Unlike frying and baking, microwaving does not produce acrylamide in potatoes,^[71] however unlike deep-frying at high-temperatures, it is of only limited effectiveness in reducing glycoalkaloid (i.e., solanine) levels.^[72] Acrylamide has been found in other microwaved products like popcorn.

Use in cleaning kitchen sponges

Studies have investigated the use of the microwave oven to clean non-metallic domestic sponges which have been thoroughly wetted. A 2006 study found that microwaving wet sponges for 2 minutes (at 1000-watt power) removed 99% of coliforms, E. coli, and MS2 phages. Bacillus cereus spores were killed at 4 minutes of microwaving.^[73]

A 2017 study was less affirmative: About 60% of the germs were killed but the remaining ones quickly re-colonized the sponge.^[74]

Issues

High temperatures

Closed containers

Closed containers, such as eggs, can explode when heated in a microwave oven due to the increased pressure from steam. Intact fresh egg yolks outside the shell also explode as a result of superheating. Insulating plastic foams of all types generally contain closed air pockets, and are generally not recommended for use in a microwave oven, as the air pockets explode and the foam (which can be toxic if consumed) may melt. Not all plastics are microwave-safe, and some plastics absorb microwaves to the point that they may become dangerously hot.^[75]

Fires

Products that are heated for too long can catch fire. Though this is inherent to any form of cooking, the rapid cooking and unattended nature of the use of microwave ovens results in additional hazard.

Superheating

In rare cases, water and other homogeneous liquids can superheat^[76][77] when heated in a microwave oven in a container with a smooth surface. That is, the liquid reaches a temperature slightly above its normal boiling point without bubbles of vapour forming inside the liquid. The boiling process can start explosively when the liquid is disturbed, such as when the user takes hold of the container to remove it from the oven or while adding solid ingredients such as powdered creamer or sugar. This can result in spontaneous boiling (nucleation) which may be violent enough to eject the boiling liquid from the container and cause severe scalding.^[78]

Metal objects

Contrary to popular assumptions, metal objects can be safely used in a microwave oven, but with some restrictions.^[79][80] Any metal or conductive object placed into the microwave oven acts as an antenna to some degree, resulting in an electric current. This causes the object to act as a heating element. This effect varies with the object’s shape and composition, and is sometimes utilized for cooking.

Any object containing pointed metal can create an electric arc (sparks) when microwaved. This includes cutlery, crumpled aluminium foil (though some foil used in microwave ovens is safe, see below), twist-ties containing metal wire, the metal wire carry-handles in oyster pails, or almost any metal formed into a poorly conductive foil or thin wire, or into a pointed shape.^[81] Forks are a good example: the tines of the fork respond to the electric field by producing high concentrations of electric charge at the tips. This has the effect of exceeding the dielectric breakdown of air, about 3 megavolts per meter (3×10⁶ V/m). The air forms a conductive plasma, which is visible as a spark. The plasma and the tines may then form a conductive loop, which may be a more effective antenna, resulting in a longer lived spark. When dielectric breakdown occurs in air, some ozone and nitrogen oxides are formed, both of which are unhealthy in large quantities.

Microwaving an individual smooth metal object without pointed ends, for example, a spoon or shallow metal pan, usually does not produce sparking. Thick metal wire racks can be part of the interior design in microwave ovens (see illustration). In a similar way, the interior wall plates with perforating holes which allow light and air into the oven, and allow interior-viewing through the oven door, are all made of conductive metal formed in a safe shape.

The effect of microwaving thin metal films can be seen clearly on a Compact Disc or DVD (particularly the factory pressed type). The microwaves induce electric currents in the metal film, which heats up, melting the plastic in the disc and leaving a visible pattern of concentric and radial scars. Similarly, porcelain with thin metal films can also be destroyed or damaged by microwaving. Aluminium foil is thick enough to be used in microwave ovens as a shield against heating parts of food items, if the foil is not badly warped. When wrinkled, aluminium foil is generally unsafe in microwaves, as manipulation of the foil causes sharp bends and gaps that invite sparking. The USDA recommends that aluminium foil used as a partial food shield in microwave oven cooking cover no more than one quarter of a food object, and be carefully smoothed to eliminate sparking hazards.^[82]

Another hazard is the resonance of the magnetron tube itself. If the microwave oven is run without an object to absorb the radiation, a standing wave forms. The energy is reflected back and forth between the tube and the cooking chamber. This may cause the tube to overload and burn out. High reflected power may also cause magnetron arcing, possibly resulting in primary power fuse failure, though such a causal relationship is not easily established. Thus, dehydrated food, or food wrapped in metal which does not arc, is problematic for overload reasons, without necessarily being a fire hazard.

Certain foods such as grapes, if properly arranged, can produce an electric arc.^[83] Prolonged arcing from food carries similar risks to arcing from other sources as noted above.

Some other objects that may conduct sparks are plastic/holographic print Thermos flasks and other heat-retaining containers (such as Starbucks novelty cups) or cups with metal lining. If any bit of the metal is exposed, all the outer shell can burst off the object or melt.^{[citation needed]}

The high electrical fields generated inside a microwave oven often can be illustrated by placing a radiometer or neon glow-bulb inside the cooking chamber, creating glowing plasma inside the low-pressure bulb of the device.

Direct microwave exposure

Further information: Microwave burn and Microwave § Effects on health

Direct microwave exposure is not generally possible, as microwaves emitted by the source in a microwave oven are confined in the oven by the material out of which the oven is constructed. Furthermore, ovens are equipped with redundant safety interlocks, which remove power from the magnetron if the door is opened. This safety mechanism is required by United States federal regulations.^[84] Tests have shown confinement of the microwaves in commercially available ovens to be so nearly universal as to make routine testing unnecessary.^[85] According to the United States Food and Drug Administration‘s Center for Devices and Radiological Health, a U.S. Federal Standard limits the amount of microwaves that can leak from an oven throughout its lifetime to 5 milliwatts of microwave radiation per square centimeter at approximately 5 cm (2 in) from the surface of the oven.^[86] This is far below the exposure level currently considered to be harmful to human health.^[87]

The radiation produced by a microwave oven is non-ionizing. It therefore does not have the cancer risks associated with ionizing radiation such as X-rays and high-energy particles. Long-term rodent studies to assess cancer risk have so far failed to identify any carcinogenicity from 2.45 GHz microwave radiation even with chronic exposure levels (i.e. large fraction of life span) far larger than humans are likely to encounter from any leaking ovens.^[88][89] However, with the oven door open, the radiation may cause damage by heating. Microwave ovens are sold with a protective interlock so that it cannot be run when the door is open or improperly latched.

Microwaves generated in microwave ovens cease to exist once the electrical power is turned off. They do not remain in the food when the power is turned off, any more than light from an electric lamp remains in the walls and furnishings of a room when the lamp is turned off. They do not make the food or the oven radioactive. In contrast with conventional cooking, the nutritional content of some foods may be altered differently, but generally in a positive way by preserving more micronutrients – see above. There is no indication of detrimental health issues associated with microwaved food.^[90]

There are, however, a few cases where people have been exposed to direct microwave radiation, either from appliance malfunction or deliberate action.^[91][92] This exposure generally results in physical burns to the body, as human tissue, particularly the outer fat and muscle layers, has a similar composition to some foods that are typically cooked in microwave ovens and so experiences similar dielectric heating effects when exposed to microwave electromagnetic radiation.

Chemical exposure

The use of unmarked plastics for microwave cooking raises the issue of plasticizers leaching into the food.^[93]

The plasticizers which received the most attention are bisphenol A (BPA) and phthalates,^[93][94] although it is unclear whether other plastic components present a toxicity risk. Other issues include melting and flammability. An alleged issue of release of dioxins into food has been dismissed^[93] as an intentional red herring distraction from actual safety issues.

Some current plastic containers and food wraps are specifically designed to resist radiation from microwaves. Products may use the term “microwave safe”, may carry a microwave symbol (three lines of waves, one above the other) or simply provide instructions for proper microwave oven use. Any of these is an indication that a product is suitable for microwaving when used in accordance with the directions provided.^[95]

Plastic containers can release microplastics into food when heated in microwave ovens.^[96]

Uneven heating

Microwave ovens are frequently used for reheating leftover food, and bacterial contamination may not be repressed if the microwave oven is used improperly. If safe temperature is not reached, this can result in foodborne illness, as with other reheating methods. While microwave ovens can destroy bacteria as well as conventional ovens can, they cook rapidly and may not cook as evenly, similar to frying or grilling, leading to a risk of some food regions failing to reach recommended temperatures. Therefore, a standing period after cooking to allow temperatures in the food to equalize is recommended, as well as the use of a food thermometer to verify internal temperatures.^[97]

Interference

Microwave ovens, although shielded for safety purposes, still emit low levels of microwave radiation. This is not harmful to humans, but can sometimes cause interference to Wi-Fi and Bluetooth and other devices that communicate on the 2.45 GHz wavebands, particularly at close range.^[98] Conventional transformer ovens do not operate continuously over the mains cycle, but can cause significant slowdowns for many metres around the oven, whereas inverter-based ovens can stop nearby networking entirely while operating.^[99]

A tablet computer, commonly shortened to tablet, is a mobile device, typically with a mobile operating system and touchscreen display processing circuitry, and a rechargeable battery in a single, thin and flat package. Tablets, being computers, have similar capabilities, but lack some input/output (I/O) abilities that others have. Modern tablets largely resemble modern smartphones, the only differences being that tablets are relatively larger than smartphones, with screens 7 inches (18 cm) or larger, measured diagonally,^[1][2][3][4] and may not support access to a cellular network. Unlike laptops (which have traditionally run off operating systems usually designed for desktops), tablets usually run mobile operating systems, alongside smartphones.

The touchscreen display is operated by gestures executed by finger or digital pen (stylus), instead of the mouse, touchpad, and keyboard of larger computers. Portable computers can be classified according to the presence and appearance of physical keyboards. Two species of tablet, the slate and booklet, do not have physical keyboards and usually accept text and other input by use of a virtual keyboard shown on their touchscreen displays. To compensate for their lack of a physical keyboard, most tablets can connect to independent physical keyboards by Bluetooth or USB; 2-in-1 PCs have keyboards, distinct from tablets.

Samsung‘s Galaxy Tab S9

The form of the tablet was conceptualized in the middle of the 20th century (Stanley Kubrick depicted fictional tablets in the 1968 science fiction film 2001: A Space Odyssey) and prototyped and developed in the last two decades of that century. In 2010, Apple released the iPad, the first mass-market tablet to achieve widespread popularity.^[5] Thereafter, tablets rapidly rose in ubiquity and soon became a large product category used for personal, educational and workplace applications.^[6] Popular uses for a tablet PC include viewing presentations, video-conferencing, reading e-books, watching movies, sharing photos and more.^[7] As of 2021 there are 1.28 billion tablet users worldwide according to data provided by Statista,^[8] while Apple holds the largest manufacturer market share followed by Samsung and Lenovo.^[9]

History

[edit]

Main article: History of tablet computers

The tablet computer and its associated operating system began with the development of pen computing.^[10] Electrical devices with data input and output on a flat information display existed as early as 1888 with the telautograph,^[11] which used a sheet of paper as display and a pen attached to electromechanical actuators. Throughout the 20th century devices with these characteristics have been imagined and created whether as blueprints, prototypes, or commercial products. In addition to many academic and research systems, several companies released commercial products in the 1980s, with various input/output types tried out.

Fictional and prototype tablets

[edit]

Tablet computers appeared in a number of works of science fiction in the second half of the 20th century; all helped to promote and disseminate the concept to a wider audience.^[12] Examples include:

• Isaac Asimov described a Calculator Pad in his novel Foundation (1951)
• Stanisław Lem described the Opton in his novel Return from the Stars (1961)
• Numerous similar devices were depicted in Gene Roddenberry‘s Star Trek: The Original Series (1966)
• Dr Who: The Dominators Educator Balan holds a tablet which he hold and inputs data into using swipe gestures.(1967)^[13]
• Arthur C. Clarke‘s newspad^[14] was depicted in Stanley Kubrick‘s film 2001: A Space Odyssey (1968)
• Douglas Adams described a tablet computer in The Hitchhiker’s Guide to the Galaxy and the associated comedy of the same name (1978)
• The science fiction TV series Star Trek: The Next Generation featured tablet computers which were designated as PADDs, notable for (as with most computers in the show) using a touchscreen interface, both with and without a stylus (1987)^[15]
• A device more powerful than today’s tablets appeared briefly in The Mote in God’s Eye (1974)^[16]
• The Star Wars franchise features datapads, first described in print in the 1991 novel Heir to the Empire, and depicted on screen in the 1999 feature film, Star Wars: Episode I – The Phantom Menace

Further, real-life projects either proposed or created tablet computers, such as:

• In 1968, computer scientist Alan Kay envisioned a KiddiComp;^[17][18] he developed and described the concept as a Dynabook in his proposal, A personal computer for children of all ages (1972),^[19] which outlines functionality similar to that supplied via a laptop computer, or (in some of its other incarnations) a tablet or slate computer, with the exception of near eternal battery life. The target audience was children.
• In 1979, the idea of a touchscreen tablet that could detect an external force applied to one point on the screen was patented in Japan by a team at Hitachi consisting of Masao Hotta, Yoshikazu Miyamoto, Norio Yokozawa and Yoshimitsu Oshima, who later received a US patent for their idea.^[20]
• In 1992, Atari showed developers the Stylus, later renamed ST-Pad. The ST-Pad was based on the TOS/GEM Atari ST platform and prototyped early handwriting recognition. Shiraz Shivji‘s company Momentus demonstrated in the same time a failed x86 MS-DOS based Pen Computer with its own graphical user interface (GUI).^[21]
• In 1994, the European Union initiated the NewsPad project, inspired by Clarke and Kubrick’s fictional work.^[22] Acorn Computers developed and delivered an ARM-based touch screen tablet computer for this program, branding it the “NewsPad”; the project ended in 1997.^[23]
• During the November 2000 COMDEX, Microsoft used the term Tablet PC to describe a prototype handheld device they were demonstrating.^[24][25][26]
• In 2001, Ericsson Mobile Communications announced an experimental product named the DelphiPad, which was developed in cooperation with the Centre for Wireless Communications in Singapore, with a touch-sensitive screen, Netscape Navigator as a web browser, and Linux as its operating system.^[27][28]

Early tablets

[edit]

Following earlier tablet computer products such as the Pencept PenPad,^[29][30] the Linus Write-Top,^[31][32] and the CIC Handwriter,^[33] in September 1989, Grid Systems released the first commercially successful tablet computer, the GridPad.^[34][35] All four products were based on extended versions of the MS-DOS operating system. In 1992, IBM announced (in April) and shipped to developers (in October) the ThinkPad 700T (2521), which ran the GO Corporation‘s PenPoint OS. Also based on PenPoint was AT&T‘s EO Personal Communicator from 1993, which ran on AT&T’s own hardware, including their own AT&T Hobbit CPU. Apple Computer launched the Apple Newton personal digital assistant in 1993. It used Apple’s own new Newton OS, initially running on hardware manufactured by Motorola and incorporating an ARM CPU, that Apple had specifically co-developed with Acorn Computers. The operating system and platform design were later licensed to Sharp and Digital Ocean, who went on to manufacture their own variants.

Pen computing was highly hyped by the media during the early 1990s. Microsoft, the dominant PC software vendor, released Windows for Pen Computing in 1992 to compete against PenPoint OS. The company launched the WinPad project, working together with OEMs such as Compaq, to create a small device with a Windows-like operating system and handwriting recognition. However, the project was abandoned two years later; instead Windows CE was released in the form of “Handheld PCs” in 1996.^[36] That year, Palm, Inc. released the first of the Palm OS based PalmPilot touch and stylus based PDA, the touch based devices initially incorporating a Motorola Dragonball (68000) CPU. Also in 1996 Fujitsu released the Stylistic 1000 tablet format PC, running Microsoft Windows 95, on a 100 MHz AMD486 DX4 CPU, with 8 MB RAM offering stylus input, with the option of connecting a conventional Keyboard and mouse. Intel announced a StrongARM^[37] processor-based touchscreen tablet computer in 1999, under the name WebPAD. It was later re-branded as the “Intel Web Tablet”.^[38] In 2000, Norwegian company Screen Media AS and the German company Dosch & Amand Gmbh released the “FreePad”.^[39] It was based on Linux and used the Opera browser. Internet access was provided by DECT DMAP, only available in Europe and provided up to 10 Mbit/s. The device had 16 MB storage, 32 MB of RAM and x86 compatible 166 MHz “Geode”-Microcontroller by National Semiconductor.^[40] The screen was 10.4″ or 12.1″ and was touch sensitive. It had slots for SIM cards to enable support of television set-up box. FreePad were sold in Norway and the Middle East; but the company was dissolved in 2003. Sony released its Airboard tablet in Japan in late 2000 with full wireless Internet capabilities.^[41][42]

In the late 1990s, Microsoft launched the Handheld PC platform using their Windows CE operating system; while most devices were not tablets, a few touch enabled tablets were released on the platform such as the Fujitsu PenCentra 130 or Siemens‘s SIMpad.^[43][44] Microsoft took a more significant approach to tablets in 2002 as it attempted to define the Microsoft Tablet PC^[45] as a mobile computer for field work in business,^[46] though their devices failed, mainly due to pricing and usability decisions that limited them to their original purpose – such as the existing devices being too heavy to be held with one hand for extended periods, and having legacy applications created for desktop interfaces and not well adapted to the slate format.^[47]

Nokia had plans for an Internet tablet since before 2000. An early model was test manufactured in 2001, the Nokia M510, which was running on EPOC and featuring an Opera browser, speakers and a 10-inch 800×600 screen, but it was not released because of fears that the market was not ready for it.^[48] Nokia entered the tablet space in May 2005 with the Nokia 770 running Maemo, a Debian-based Linux distribution custom-made for their Internet tablet line. The user interface and application framework layer, named Hildon, was an early instance of a software platform for generic computing in a tablet device intended for internet consumption.^[49] But Nokia did not commit to it as their only platform for their future mobile devices and the project competed against other in-house platforms and later replaced it with the Series 60.^[50] Nokia used the term internet tablet to refer to a portable information appliance that focused on Internet use and media consumption, in the range between a personal digital assistant (PDA) and an Ultra-Mobile PC (UMPC). They made two mobile phones, the N900 that runs Maemo, and N9 that run Meego.^[51]

Before the release of iPad, Axiotron introduced^[52] an aftermarket, heavily modified Apple MacBook called Modbook, a Mac OS X-based tablet computer. The Modbook uses Apple’s Inkwell for handwriting and gesture recognition, and uses digitization hardware from Wacom. To get Mac OS X to talk to the digitizer on the integrated tablet, the Modbook was supplied with a third-party driver.^[53]

Following the launch of the Ultra-mobile PC, Intel began the Mobile Internet Device initiative, which took the same hardware and combined it with a tabletized Linux configuration. Intel codeveloped the lightweight Moblin (mobile Linux) operating system following the successful launch of the Atom CPU series on netbooks. In 2010, Nokia and Intel combined the Maemo and Moblin projects to form MeeGo, a Linux-based operating system supports netbooks and tablets. The first tablet using MeeGo was the Neofonie WeTab launched September 2010 in Germany. The WeTab used an extended version of the MeeGo operating system called WeTab OS. WeTab OS adds runtimes for Android and Adobe AIR and provides a proprietary user interface optimized for the WeTab device. On September 27, 2011, the Linux Foundation announced that MeeGo would be replaced in 2012 by Tizen.^[54]

Modern tablets

[edit]

Android was the first of the 2000s-era dominating platforms for tablet computers to reach the market. In 2008, the first plans for Android-based tablets appeared. The first products were released in 2009. Among them was the Archos 5, a pocket-sized model with a 5-inch touchscreen, that was first released with a proprietary operating system and later (in 2009) released with Android 1.4. The Camangi WebStation was released in Q2 2009. The first LTE Android tablet appeared late 2009 and was made by ICD for Verizon. This unit was called the Ultra, but a version called Vega was released around the same time. Ultra had a 7-inch display while Vega’s was 15 inches. Many more products followed in 2010. Several manufacturers waited for Android Honeycomb, specifically adapted for use with tablets, which debuted in February 2011.

Apple is often credited for defining a new class of consumer device with the iPad,^[55] which shaped the commercial market for tablets in the following years,^[56] and was the most successful tablet at the time of its release. iPads and competing devices were tested by the U.S. military in 2011^[57] and cleared for secure use in 2013.^[58] Its debut in 2010 pushed tablets into the mainstream.^[59][60] Samsung‘s Galaxy Tab and others followed, continuing the trends towards the features listed above. In March 2012, PC Magazine reported that 31% of U.S. Internet users owned a tablet, used mainly for viewing published content such as video and news.^[61] The top-selling line of devices was Apple’s iPad with 100 million sold between its release in April 2010 and mid-October 2012,^[62] but iPad market share (number of units) dropped to 36% in 2013 with Android tablets climbing to 62%. Android tablet sales volume was 121 million devices, plus 52 million, between 2012 and 2013 respectively.^[63] Individual brands of Android operating system devices or compatibles follow iPad with Amazon’s Kindle Fire with 7 million, and Barnes & Noble’s Nook with 5 million.^[64][65][66]

The BlackBerry PlayBook was announced in September 2010 that ran the BlackBerry Tablet OS.^[67] The BlackBerry PlayBook was officially released to US and Canadian consumers on April 19, 2011. Hewlett-Packard announced that the TouchPad, running WebOS 3.0 on a 1.2 GHz Qualcomm Snapdragon CPU, would be released in June 2011. On August 18, 2011, HP announced the discontinuation of the TouchPad, due to sluggish sales.^[68] In 2013, the Mozilla Foundation announced a prototype tablet model with Foxconn which ran on Firefox OS.^[69] Firefox OS was discontinued in 2016.^[70] The Canonical hinted that Ubuntu would be available on tablets by 2014.^[71] In February 2016, there was a commercial release of the BQ Aquaris Ubuntu tablet using the Ubuntu Touch operating system.^[72] Canonical terminated support for the project due to lack of market interest on April 5, 2017^[73][74] and it was then adopted by the UBports as a community project.^[75]

As of February 2014, 83% of mobile app developers were targeting tablets,^[76] but 93% of developers were targeting smartphones. By 2014, around 23% of B2B companies were said to have deployed tablets for sales-related activities, according to a survey report by Corporate Visions.^[77] The iPad held majority use in North America, Western Europe, Japan, Australia, and most of the Americas. Android tablets were more popular in most of Asia (China and Russia an exception), Africa and Eastern Europe. In 2015 tablet sales did not increase. Apple remained the largest seller but its market share declined below 25%.^[78] Samsung vice president Gary Riding said early in 2016 that tablets were only doing well among those using them for work. Newer models were more expensive and designed for a keyboard and stylus, which reflected the changing uses.^[79] As of early 2016, Android reigned over the market with 65%. Apple took the number 2 spot with 26%, and Windows took a distant third with the remaining 9%.^[80] In 2018, out of 4.4 billion computing devices Android accounted for 2 billion, iOS for 1 billion, and the remainder were PCs, in various forms (desktop, notebook, or tablet), running various operating systems (Windows, macOS, ChromeOS, Linux, etc.).^[81]

Since the early 2020s, various companies such as Samsung are beginning to introduce foldable technology into their tablets.^[82]

Types

[edit]

Tablets can be loosely grouped into several categories by physical size, kind of operating system installed, input and output technology, and uses.^[83]

Slate

[edit]

The size of a slate varies, but slates begin at 6 inches (approximately 15 cm).^[84] Some models in the larger than 10-inch (25 cm) category include the Samsung Galaxy Tab Pro 12.2 at 12.2 inches (31 cm), the Toshiba Excite at 13.3 inches (33 cm)^[85] and the Dell XPS 18 at 18.4 inches (47 cm).^[86] As of March 2013, the thinnest tablet on the market was the Sony Xperia Tablet Z at only 0.27 inches (6.9 mm) thick.^[87] On September 9, 2015, Apple released the iPad Pro with a 12.9 inches (33 cm) screen size, larger than the regular iPad.^[88]

Mini tablet

[edit]

Mini tablets are smaller and weigh less than slates, with typical screen sizes between 7–8 inches (18–20 cm). The first commercially successful mini tablets were introduced by Amazon.com (Kindle Fire), Barnes & Noble (Nook Tablet), and Samsung (Galaxy Tab) in 2011; and by Google (Nexus 7) in 2012. They operate identically to ordinary tablets but have lower specifications compared to them.

On September 14, 2012, Amazon, Inc. released an upgraded version of the Kindle Fire, the Kindle Fire HD, with higher screen resolution and more features compared to its predecessor, yet remaining only 7 inches.^[89] In October 2012, Apple released the iPad Mini with a 7.9-inch screen size, about 2 inches smaller than the regular iPad, but less powerful than the then current iPad 3.^[90] On July 24, 2013, Google released an upgraded version of the Nexus 7, with FHD display, dual cameras, stereo speakers, more color accuracy, performance improvement, built-in wireless charging, and a variant with 4G LTE support for AT&T, T-Mobile, and Verizon. In September 2013, Amazon further updated the Fire tablet with the Kindle Fire HDX. In November 2013, Apple released the iPad Mini 2, which remained at 7.9 inches and nearly matched the hardware of the iPad Air.

Phablet

[edit]

Main article: Phablet

Smartphones and tablets are similar devices, differentiated by the former typically having smaller screens and most tablets lacking cellular network capability. Since 2010, crossover touchscreen smartphones with screens larger than 5 inches have been released. That size is generally considered larger than a traditional smartphone, creating the hybrid category of the phablet by Forbes^[91] and other publications. “Phablet” is a portmanteau of “phone” and “tablet”.

At the time of the introduction of the first phablets, they had screens of 5.3 to 5.5 inches, but as of 2017 screen sizes up to 5.5 inches are considered typical. Examples of phablets from 2017 and onward are the Samsung Galaxy Note series (newer models of 5.7 inches), the LG V10/V20 (5.7 inches), the Sony Xperia XA Ultra (6 inches), the Huawei Mate 9 (5.9 inches), and the Huawei Honor (MediaPad) X2 (7 inches).

2-in-1

[edit]

Main article: 2-in-1 PC

A 2-in-1 PC is a hybrid or combination of a tablet and laptop computer that has features of both. Distinct from tablets, 2-in-1 PCs all have physical keyboards, but they are either concealable by folding them back and under the touchscreen (“2-in-1 convertible”) or detachable (“2-in-1 detachable”). 2-in-1s typically also can display a virtual keyboard on their touchscreens when their physical keyboards are concealed or detached. Some 2-in-1s have processors and operating systems like those of laptops, such as Windows 10, while having the flexibility of operation as a tablet. Further, 2-in-1s may have typical laptop I/O ports, such as USB 3 and DisplayPort, and may connect to traditional PC peripheral devices and external displays. Simple tablets are mainly used as media consumption devices, while 2-in-1s have capacity for both media consumption and content creation, and thus 2-in-1s are often called laptop or desktop replacement computers.^[92]

There are two species of 2-in-1s:

• Convertibles have a chassis design by which their physical keyboard may be concealed by flipping/folding the keyboard behind the chassis. Examples include 2-in-1 PCs of the Lenovo Yoga series.
• Detachables or Hybrids have physical keyboards that may be detached from their chassis, even while the 2-in-1 is operating. Examples include 2-in-1 PCs of the Asus Transformer Pad and Book series, the iPad Pro, and the Microsoft Surface Book and Surface Pro.

Gaming tablet

[edit]

Some tablets are modified by adding physical gamepad buttons such as D-pad and thumb sticks for better gaming experience combined with the touchscreen and all other features of a typical tablet computer. Most of these tablets are targeted to run native OS games and emulator games. Nvidia‘s Shield Tablet, with an 8-inch (200 mm) display, and running Android, is an example. It runs Android games purchased from Google Play store. PC games can also be streamed to the tablet from computers with some higher end models of Nvidia-powered video cards. The Nintendo Switch hybrid console is also a gaming tablet that runs on its own system software, features detachable Joy-Con controllers with motion controls and three gaming modes: table-top mode using its kickstand, traditional docked/TV mode and handheld mode. While not entirely an actual tablet form factor due to their sizes, some other handheld console including the smaller version of Nintendo Switch, the Nintendo Switch Lite, and PlayStation Vita are treated as an gaming tablet or tablet replacement by community and reviewer/publisher due to their capabilities on browsing the internet and multimedia capabilities.^[93]

Booklet

[edit]

Booklets are dual-touchscreen tablet computers with a clamshell design that can fold like a laptop. Examples include the Microsoft Courier, which was discontinued in 2010,^[94][95] the Sony Tablet P (considered a flop),^[96] and the Toshiba Libretto W100.

Customized business tablet

[edit]

Customized business tablets are built specifically for a business customer’s particular needs from a hardware and software perspective, and delivered in a business-to-business transaction. For example, in hardware, a transportation company may find that the consumer-grade GPS module in an off-the-shelf tablet provides insufficient accuracy, so a tablet can be customized and embedded with a professional-grade antenna to provide a better GPS signal. Such tablets may also be ruggedized for field use. For a software example, the same transportation company might remove certain software functions in the Android system, such as the web browser, to reduce costs from needless cellular network data consumption of an employee, and add custom package management software. Other applications may call for a resistive touchscreen and other special hardware and software.

A table ordering tablet is a touchscreen tablet computer designed for use in casual restaurants.^[97] Such devices allow users to order food and drinks, play games and pay their bill. Since 2013, restaurant chains including Chili’s,^[98] Olive Garden^[99] and Red Robin^[100] have adopted them. As of 2014, the two most popular brands were Ziosk and Presto.^[101] The devices have been criticized by servers who claim that some restaurants determine their hours based on customer feedback in areas unrelated to service.^[102]

E-reader

[edit]

Any device that can display text on a screen may act as an E-reader. While traditionally E-readers are designed primarily for the purpose of reading digital e-books and periodicals, modern E-readers that use a mobile operating system such as Android have incorporated modern functionally including internet browsing and multimedia capabilities; for example Huawei MatePad Paper is a tablet that uses e-ink instead of typical LCD or LED panel, hence focusing on the reading digital content while maintaining the internet and multimedia capabilities. Some E-reader such as PocketBook InkPad Color and ONYX BOOX NOVA 3 Color even came with colored e-ink panel and speaker which allowed for higher degree of multimedia consumption and video playback.

The Kindle line from Amazon was originally limited to E-reading capabilities; however, an update to their Kindle firmware added the ability to browse the Internet and play audio, allowing Kindles to be alternatives to a traditional tablet, in some cases, with a more readable e-ink panel and greater battery life, and providing the user with access to wider multimedia capabilities compared to the older model.

Hardware

[edit]

System architecture

[edit]

See also: Comparison of tablet computers

Two major architectures dominate the tablet market,^[103] ARM Ltd.‘s ARM architecture and Intel’s and AMD’s x86. Intel’s x86, including x86-64 has powered the “IBM compatible” PC since 1981 and Apple’s Macintosh computers since 2006. The CPUs have been incorporated into tablet PCs over the years and generally offer greater performance along with the ability to run full versions of Microsoft Windows, along with Windows desktop and enterprise applications. Non-Windows based x86 tablets include the JooJoo. Intel announced plans to enter the tablet market with its Atom in 2010.^[104][105] In October 2013, Intel’s foundry operation announced plans to build FPGA-based quad cores for ARM and x86 processors.^[106]

ARM has been the CPU architecture of choice for manufacturers of smartphones (95% ARM), PDAs, digital cameras (80% ARM), set-top boxes, DSL routers, smart televisions (70% ARM), storage devices and tablet computers (95% ARM).^{[107][independent source needed]} This dominance began with the release of the mobile-focused and comparatively power-efficient 32-bit ARM610 processor originally designed for the Apple Newton in 1993 and ARM3-using Acorn A4 laptop in 1992. The chip was adopted by Psion, Palm and Nokia for PDAs and later smartphones, camera phones, cameras, etc. ARM’s licensing model supported this success by allowing device manufacturers to license, alter and fabricate custom SoC derivatives tailored to their own products. This has helped manufacturers extend battery life and shrink component count along with the size of devices.

The multiple licensees ensured that multiple fabricators could supply near-identical products, while encouraging price competition. This forced unit prices down to a fraction of their x86 equivalents. The architecture has historically had limited support from Microsoft, with only Windows CE available, but with the 2012 release of Windows 8, Microsoft announced added support for the architecture, shipping their own ARM-based tablet computer, branded the Microsoft Surface, as well as an x86-64 Intel Core i5 variant branded as Microsoft Surface Pro.^{[108][109][110][111]} Intel tablet chip sales were 1 million units in 2012, and 12 million units in 2013.^[112] Intel chairman Andy Bryant has stated that its 2014 goal is to quadruple its tablet chip sales to 40 million units by the end of that year,^[113] as an investment for 2015.^{[114][115][116][117]}

See also: Mobile Internet Device § Intel MID Platforms

Display

[edit]

A key component among tablet computers is touch input on a touchscreen display. This allows the user to navigate easily and type with a virtual keyboard on the screen or press other icons on the screen to open apps or files. The first tablet to do this was the Linus Write-Top by Linus Technologies; the tablet featured both a stylus, a pen-like tool to aid with precision in a touchscreen device, as well as handwriting recognition.^[31][118] The system must respond to on-screen touches rather than clicks of a keyboard or mouse. This operation makes precise use of our eye–hand coordination.^{[119][120][121]}

Touchscreens usually come in one of two forms:

• Resistive touchscreens are passive and respond to pressure on the screen. They allow a high level of precision, useful in emulating a pointer (as is common in tablet computers) but may require calibration. Because of the high resolution, a stylus or fingernail is often used. Stylus-oriented systems are less suited to multi-touch.
• Capacitive touchscreens tend to be less accurate, but more responsive than resistive devices. Because they require a conductive material, such as a fingertip, for input, they are not common among stylus-oriented devices but are prominent on consumer devices. Most finger-driven capacitive screens do not currently support pressure input (except for the iPhone 6S and later models), but some tablets use a pressure-sensitive stylus or active pen.^[122]
• Some tablets can recognize individual palms, while some professional-grade tablets use pressure-sensitive films, such as those on graphics tablets. Some capacitive touch-screens can detect the size of the touched area and the pressure used.^[123]

Since mid-2010s, most tablets use capacitive touchscreens with multi-touch, unlike earlier resistive touchscreen devices which users needed styluses to perform inputs.

There are also electronic paper tablets such as Sony Digital Paper DPTS1 and reMarkable that use E ink for its display technology.

Handwriting recognition

[edit]

Many tablets support a stylus and support handwriting recognition. Wacom and N-trig digital pens provide approximately 2500 DPI resolution for handwriting, exceeding the resolution of capacitive touch screens by more than a factor of 10. These pens also support pressure sensitivity, allowing for “variable-width stroke-based” characters, such as Chinese/Japanese/Korean writing, due to their built-in capability of “pressure sensing”. Pressure is also used in digital art applications such as Autodesk Sketchbook.^[124][125] Apps exist on both iOS and Android platforms for handwriting recognition and in 2015 Google introduced its own handwriting input with support for 82 languages.^[126]

Other features

[edit]

After 2007, with access to capacitive screens and the success of the iPhone, other features became common, such as multi-touch features (in which the user can touch the screen in multiple places to trigger actions and other natural user interface features, as well as flash memory solid state storage and “instant on” warm-booting; external USB and Bluetooth keyboards defined tablets.

Most tablets released since mid-2010 use a version of an ARM processor for longer battery life. The ARM Cortex family is powerful enough for tasks such as internet browsing, light creative and production work and mobile games.^[127]

Other features are: High-definition, anti-glare display, touchscreen, lower weight and longer battery life than a comparably-sized laptop, wireless local area and internet connectivity (usually with Wi-Fi standard and optional mobile broadband), Bluetooth for connecting peripherals and communicating with local devices, ports for wired connections and charging, for example USB ports, Early devices had IR support and could work as a TV remote controller, docking station, keyboard and added connectivity, on-board flash memory, ports for removable storage, various cloud storage services for backup and syncing data across devices, local storage on a local area network (LAN).

• Speech recognition Google introduced voice input in Android 2.1 in 2009 and voice actions in 2.2 in 2010, with up to five languages (now around 40).^[128] Siri was introduced as a system-wide personal assistant on the iPhone 4S in 2011 and now supports nearly 20 languages. In both cases, the voice input is sent to central servers to perform general speech recognition and thus requires a network connection for more than simple commands.
• Near-field communication with other compatible devices including ISO/IEC 14443 RFID tags.

Software

[edit]

Current tablet operating systems

[edit]

Tablets, like conventional PCs, use several different operating systems, though dual-booting is rare. Tablet operating systems come in two classes:

• Desktop computer operating systems
• Mobile operating systems

Desktop OS-based tablets are currently thicker and heavier. They require more storage and more cooling and give less battery life. They can run processor-intensive graphical applications in addition to mobile apps, and have more ports.^[129]

Mobile-based tablets are the reverse, and run only mobile apps. They can use battery life conservatively because the processor is significantly smaller. This allows the battery to last much longer than the common laptop.^[130]

In Q1 2018, Android tablets had 62% of the market, Apple’s iOS had 23.4% of the market and Windows 10 had 14.6% of the market.^[131] In late 2021, iOS has 55% use worldwide (varies by continent, e.g. below 50% in South America and Africa) and Android 45% use. Still, Android tablets have more use than iOS in virtually all countries, except for e.g. the U.S. and China.^{[132][133][134]}

Android

[edit]

Main article: Android (operating system)

Android is a Linux-based operating system that Google offers as open source under the Apache license. It is designed primarily for mobile devices such as smartphones and tablet computers. Android supports low-cost ARM systems and others. The first tablets running Android were released in 2009.^[135] Vendors such as Motorola^[136] and Lenovo^[137] delayed deployment of their tablets until after 2011, when Android was reworked to include more tablet features.^{[138][139][140]} Android 3.0 (Honeycomb), released in 2011 and later versions support larger screen sizes, mainly tablets, and have access to the Google Play service. Android includes operating system, middleware and key applications. Other vendors sell customized Android tablets, such as Kindle Fire and Nook, which are used to consume mobile content and provide their own app store, rather than using the larger Google Play system, thereby fragmenting the Android market.^[141] In 2022 Google began to re-emphasize in-house Android tablet development — at this point, a multi-year commitment.^[142]

Android Go

[edit]

Main article: Comparison of Android Go products § Tablet computers

A few tablet computers are shipped with Android Go.

Fire OS

[edit]

As mentioned above, Amazon Fire OS is an Android-based mobile operating system produced by Amazon for its Fire range of tablets. It is forked from Android. Fire OS primarily centers on content consumption, with a customized user interface and heavy ties to content available from Amazon’s own storefronts and services.

ChromeOS

[edit]

Several devices that run ChromeOS came on the market in 2017–2019, as tablets, or as 2-in-1s with touchscreen and 360-degree hinge.^[143]

HarmonyOS

[edit]

HarmonyOS (HMOS) (Chinese: 鸿蒙; pinyin: Hóngméng) is a distributed operating system developed by Huawei to collaborate and interconnect with multiple smart devices on the Internet of Things (IoT) ecosystem.^[144][145] In its current multi-kernel design, the operating system selects suitable kernels from the abstraction layer for devices with diverse resources.^{[145][146][147]} For IoT devices, the system is known to be based on LiteOS kernel; while for smartphones and tablets, it is based on a Linux kernel layer with AOSP libraries to support Android application package (APK) apps using Android Runtime (ART) through the Ark Compiler, in addition to native HarmonyOS apps built via integrated development environment (IDE) known as DevEco Studio.^[148][149]

iPadOS

[edit]

Main articles: iPad, iPadOS, and iOS

The iPad runs on iPadOS. Prior to the introduction of iPadOS in 2019, the iPad ran iOS, which was created for the iPhone and iPod Touch. The first iPad was released in 2010.^[150] Although built on the same underlying Unix implementation as macOS, its user interface is radically different. iPadOS is designed for touch input from the user’s fingers and has none of the features that required a stylus on earlier tablets. Apple introduced multi-touch gestures, such as moving two fingers apart or together to zoom in or out, also termed pinch to zoom.^[151] iPadOS and iOS are built for the ARM architecture.^[152]

Kindle firmware

[edit]

Main article: Amazon Kindle

Kindle firmware is a mobile operating system specifically designed for Amazon Kindle e-readers. It is based on a custom Linux kernel; however, it is entirely closed-source and proprietary, and only runs on Amazon Kindle line up manufactured under the Amazon brand.

Nintendo Switch system software

[edit]

The Nintendo Switch system software (also known by its codename Horizon) is an updatable firmware and operating system used by the Nintendo Switch hybrid video game console/tablet and Nintendo Switch Lite handheld game console. It is based on a proprietary microkernel. The UI includes a HOME screen, consisting of the top bar, the screenshot viewer (“Album”), and shortcuts to the Nintendo eShop, News, and Settings.

PlayStation Vita system software

[edit]

The PlayStation Vita system software is the official firmware and operating system for the PlayStation Vita and PlayStation TV video game consoles. It uses the LiveArea as its graphical shell. The PlayStation Vita system software has one optional add-on component, the PlayStation Mobile Runtime Package. The system is built on a Unix-base which is derived from FreeBSD and NetBSD. Due to it capabilities on browsing the internet and multimedia capabilities, it is treat as an gaming tablet or tablet replacement by community and reviewer/publisher.

Ubuntu Touch

[edit]

Main article: Ubuntu Touch

Ubuntu Touch is an open-source (GPL) mobile version of the Ubuntu operating system^[145] originally developed in 2013 by Canonical Ltd. and continued by the non-profit UBports Foundation in 2017.^[153][154] Ubuntu Touch can run on a pure GNU/Linux base on phones with the required drivers, such as the Librem 5^[155] and the PinePhone.^[156] To enable hardware that was originally shipped with Android, Ubuntu Touch makes use of the Android Linux kernel, using Android drivers and services via an LXC container, but does not use any of the Java-like code of Android.^[157][158] As of February 2022, Ubuntu Touch is available on 78 phones and tablets.^[145][159] The UBports Installer serves as an easy-to-use tool to allow inexperienced users to install the operating system on third-party devices without damaging their hardware.^[145][160]

Windows

[edit]

Main article: Windows 10

Following Windows for Pen Computing for Windows 3.1 in 1991, Microsoft supported tablets running Windows XP under the Microsoft Tablet PC name.^[161] Microsoft Tablet PCs were pen-based, fully functional x86 PCs with handwriting and voice recognition functionality.^[162] Windows XP Tablet PC Edition provided pen support. Tablet support was added to both Home and Business versions of Windows Vista and Windows 7. Tablets running Windows could use the touchscreen for mouse input, hand writing recognition and gesture support. Following Tablet PC, Microsoft announced the Ultra-mobile PC initiative in 2006 which brought Windows tablets to a smaller, touch-centric form factor.^[163][164] In 2008, Microsoft showed a prototype of a two-screen tablet called Microsoft Courier, but cancelled the project.

In 2012, Microsoft released Windows 8, which features significant changes to various aspects of the operating system’s user interface and platform which are designed for touch-based devices such as tablets. The operating system also introduced an application store and a new style of application optimized primarily for use on tablets.^[165][166] Microsoft also introduced Windows RT, an edition of Windows 8 for use on ARM-based devices.^[167] The launch of Windows 8 and RT was accompanied by the release of devices with the two operating systems by various manufacturers (including Microsoft themselves, with the release of Surface), such as slate tablets, hybrids, and convertibles.^[168]

Released in July 2015, Windows 10 introduces what Microsoft described as “universal apps“; expanding on Metro-style apps, these apps can be designed to run across multiple Microsoft product families with nearly identical code‍ – ‌including PCs, tablets, smartphones, embedded systems, Xbox One, Surface Hub and Windows Holographic. The Windows user interface was revised to handle transitions between a mouse-oriented interface and a touchscreen-optimized interface based on available input devices‍ – ‌particularly on 2-in-1 PCs; both interfaces include an updated Start menu. Windows 10 replaced all earlier editions of Windows.^[169][170]

Hybrid OS operation

[edit]

Several hardware companies have built hybrid devices with the possibility to work with both Android and Windows Phone operating systems (or in rare cases Windows 8.1, as with the, by now cancelled, Asus Transformer Book Duet), while Ars Technica stated: “dual-OS devices are always terrible products. Windows and Android almost never cross-communicate, so any dual-OS device means dealing with separate apps, data, and storage pools and completely different UI paradigms. So from a consumer perspective, Microsoft and Google are really just saving OEMs from producing tons of clunky devices that no one will want.”^[171]

Discontinued tablet operating systems

[edit]

BlackBerry 10

[edit]

BlackBerry 10 (based on the QNX OS) is from BlackBerry. As a smartphone OS, it is closed-source and proprietary, and only runs on phones and tablets manufactured by BlackBerry.

One of the dominant platforms in the world in the late 2000s, its global market share was reduced significantly by the mid-2010s. In late 2016, BlackBerry announced that it will continue to support the OS, with a promise to release 10.3.3.^[172][173] Therefore, BlackBerry 10 would not receive any major updates as BlackBerry and its partners would focus more on their Android base development.^[174]

BlackBerry Tablet OS

[edit]

BlackBerry Tablet OS is an operating system from BlackBerry Ltd based on the QNX Neutrino real-time operating system designed to run Adobe AIR and BlackBerry WebWorks applications, currently available for the BlackBerry PlayBook tablet computer. The BlackBerry Tablet OS is the first tablet running an operating system from QNX (now a subsidiary of RIM^[175]).

BlackBerry Tablet OS supports standard BlackBerry Java applications. Support for Android apps has also been announced, through sandbox “app players” which can be ported by developers or installed through sideloading by users.^[176][177] A BlackBerry Tablet OS Native Development Kit, to develop native applications with the GNU toolchain is currently in closed beta testing. The first device to run BlackBerry Tablet OS was the BlackBerry PlayBook tablet computer.^[178]

Application store

[edit]

See also: App store

Apps that do not come pre-installed with the system are supplied through online distribution. These sources, termed app stores, provide centralized catalogs of software and allow “one click” on-device software purchasing, installation and updates.^[179][180]

Mobile device suppliers may adopt a “walled garden” approach, wherein the supplier controls what software applications (“apps”) are available. Software development kits are restricted to approved software developers. This can be used to reduce the impact of malware, provide software with an approved content rating, control application quality and exclude competing vendors.^[181] Apple, Google, Amazon, Microsoft and Barnes & Noble all adopted the strategy. B&N originally allowed arbitrary apps to be installed,^{[182][183][184]} but, in December 2011, excluded third parties.^{[185][186][187][188]} Apple and IBM have agreed to cooperate in cross-selling IBM-developed applications for iPads and iPhones in enterprise-level accounts.^[189] Proponents of open source software say that the iPad (or such “walled garden” app store approach) violates the spirit of personal control that traditional personal computers have always provided.^{[190][191][192]}

Sales

[edit]

Around 2010, tablet use by businesses jumped, as business began to use them for conferences, events, and trade shows. In 2012, Intel reported that their tablet program improved productivity for about 19,000 of their employees by an average of 57 minutes a day.^[193] In October 2012, display screen shipments for tablets began surpassing shipments for laptop display screens.^[194] Tablets became increasingly used in the construction industry to look at blueprints, field documentation and other relevant information on the device instead of carrying around large amounts of paper.^[195] Time described the product’s popularity as a “global tablet craze” in a November 2012 article.^[196]

As of the start of 2014, 44% of US online consumers owned tablets,^[197] a significant jump from 5% in 2011.^[198] Tablet use also became increasingly common among children. A 2014 survey found that mobiles were the most frequently used object for play among American children under the age of 12. Mobiles were used more often in play than video game consoles, board games, puzzles, play vehicles, blocks and dolls/action figures. Despite this, the majority of parents said that a mobile was “never” or only “sometimes” a toy.^[199] As of 2014, nearly two-thirds of American 2- to 10-year-olds have access to a tablet or e-reader.^[200] The large use of tablets by adults is as a personal internet-connected TV.^[201] A 2015 study found that a third of children under five have their own tablet device.^[202]

After a fast rise in sales during the early 2010s, the tablet market had plateaued in 2015^[203] and by Q3 2018^[204][205] sales had declined by 35% from its Q3 2014 peak.^[206] In spite of this, tablet sales worldwide had surpassed sales of desktop computers in 2017,^[207] and worldwide PC sales were flat for the first quarter of 2018.^[208] In 2020 the tablet market saw a large surge in sales with 164 million tablet units being shipped worldwide due to a large demand for work from home and online learning.^[209]

	2010[210]	2011[211]	2012[212]	2013[212]	2014[213]	2015[214]	2016[215]	2017[216]	2018[217]	2019[217]
Units (M)	17.6	60.0	116.3	195.4	216.0 (sales) 229.6 (shipments)	207.2	174.8	163.5	146.2	144.1
Growth (pct.)	N/A	240.9	93.8	68.0	10.5 (sales)4.4 (shipments)	−10.1	−15.6	−6.5	−11.4	−1.5

	2020[218]	2021[9]	2022[219]	2023[220]	2024[221]
Units (M)	164.1	168.8	162.8	128.5	147.6
Growth (pct.)	13.6	3.2	−3.3	−20.5	9.0

By manufacturer

[edit]

Global tablet market share by unit shipments, percent (2011–2019)
Rank	Q3 2011[222]		Q3 2012[223]		Q3 2013[224]		Q3 2014[225]		Q3 2015[226]		Q3 2016[227]		Q3 2017[228]		Q3 2018[229]		Q3 2019[230]
1	Apple	61.5	Apple	50.4	Apple	29.6	Apple	22.8	Apple	20.3	Apple	21.5	Apple	25.8	Apple	26.6	Apple	31.4
2	Samsung	5.6	Samsung	18.4	Samsung	20.4	Samsung	18.3	Samsung	16.5	Samsung	15.1	Samsung	15.0	Samsung	14.6	Amazon	14.5
3	HP	5.0	Amazon	9.0	Asus	7.4	Asus	6.5	Lenovo	6.3	Amazon	7.3	Amazon	10.9	Amazon	12.0	Samsung	12.3
4	Barnes & Noble	4.5	Asus	8.6	Lenovo	4.8	Lenovo	5.7	Asus	4.0	Lenovo	6.3	Huawei	7.5	Huawei	8.9	Huawei	9.5
5	Asus	4.0	Lenovo	1.4	Acer	2.5	RCA	6.9	Huawei	3.7	Huawei	5.6	Lenovo	7.4	Lenovo	6.3	Lenovo	6.7
Others				12.2		35.3		41.8		49.1		44.2		33.3		31.6		25.5

Global tablet market share by unit shipments, percent (2020–present)
Rank	Q3 2020[231]		Q3 2021[232]		Q3 2022[233]		Q3 2023[234]		Q3 2024[235]
1	Apple	29.2	Apple	34.6	Apple	37.5	Apple	37.5	Apple	31.7
2	Samsung	19.8	Samsung	17.7	Samsung	18.4	Samsung	18.0	Samsung	17.9
3	Amazon	11.4	Amazon	11.1	Amazon	11.1	Lenovo	7.9	Amazon	11.6
4	Huawei	10.2	Lenovo	10.1	Lenovo	7.0	Huawei	6.8	Huawei	8.2
5	Lenovo	8.6	Huawei	5.4	Huawei	6.2	Amazon	6.5	Lenovo	7.6
Others		20.9		21.1		19.7		23.3		22.9

By operating system

[edit]

According to a survey conducted by the Online Publishers Association (OPA) now called Digital Content Next (DCN) in March 2012, it found that 72% of tablet owners had an iPad, while 32% had an Android tablet. By 2012, Android tablet adoption had increased. 52% of tablet owners owned an iPad, while 51% owned an Android-powered tablet (percentages do not add up to 100% because some tablet owners own more than one type).^[236] By end of 2013, Android’s market share rose to 61.9%, followed by iOS at 36%.^[237] By late 2014, Android’s market share rose to 72%, followed by iOS at 22.3% and Windows at 5.7%.^[238] As of early 2016, Android has 65% marketshare, Apple has 26% and Windows has 9% marketshare.^[80] In Q1 2018, Android tablets had 62% of the market, Apple’s iOS had 23.4% of the market and Windows 10 had 14.6% of the market.^[131]

	Market share(Q3 2022)
Android	49%
iPadOS	38%
Windows	11%
Others	2%

Source: Strategy Analytics^[239]

Use

[edit]

Sleep

[edit]

Main article: Electronic media and sleep

The blue wavelength of light from back-lit tablets may impact one’s ability to fall asleep when reading at night, through the suppression of melatonin.^[240] Experts at Harvard Medical School suggest limiting tablets for reading use in the evening. Those who have a delayed body clock, such as teenagers, which makes them prone to stay up late in the evening and sleep later in the morning, may be at particular risk for increases in sleep deficiencies.^[241] A PC app such as F.lux and Android apps such as CF.lumen^[242] and Twilight^[243] attempt to decrease the impact on sleep by filtering blue wavelengths from the display. iOS 9.3 includes Night Shift that shifts the colors of the device’s display to be warmer during the later hours.^[244]

By plane

[edit]

Because of, among other things, electromagnetic waves emitted by this type of device, the use of any type of electronic device during the take-off and landing phases was totally prohibited on board commercial flights. On November 13, 2013, the European Aviation Safety Agency (EASA) announced that the use of mobile terminals could be authorized on the flights of European airlines during these phases from 2014 onwards, on the condition that the cellular functions are deactivated (“airplane” mode activated).^[245] In September 2014, EASA issued guidance that allows EU airlines to permit use of tablets, e-readers, smartphones, and other portable electronic devices to stay on without the need to be in airplane mode during all parts of EU flights; however, each airline has to decide to allow this behavior.^[246] In the U.S., the Federal Aviation Administration allowed use of portable electronic devices during all parts of flights while in airplane mode in late 2013.^[247]

Tourism

[edit]

Some French historical monuments are equipped with digital tactile tablets called “HistoPad”.^[248] It is an application integrated with an iPad Mini offering an interaction in augmented and virtual reality with several pieces of the visit, the visitor being able to take control of their visit in an interactive and personalized way.

Professional use for specific sectors

[edit]

Some professionals – for example, in the construction industry, insurance experts, lifeguards or surveyors – use so-called rugged shelf models in the field that can withstand extreme hot or cold shocks or climatic environments. Some units are hardened against drops and screen breakage. Satellite-connectivity-equipped tablets such as the Thorium X,^[249] for example, can be used in areas where there is no other connectivity. This is a valuable feature in the aeronautical and military realms. For example, United States Army helicopter pilots are moving to tablets as electronic flight bags, which confer the advantages of rapid, convenient synchronization of large groups of users, and the seamless updating of information.^[250] US Army chaplains who are deployed in the field with the troops cite the accessibility of Army regulations, field manuals, and other critical information to help with their services; however, power generation, speakers, and a tablet rucksack are also necessary for the chaplains.^[251]