1.
Mechanical calculator
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A mechanical calculator, or calculating machine, was a mechanical device used to perform automatically the basic operations of arithmetic. Most mechanical calculators were comparable in size to small computers and have been rendered obsolete by the advent of the electronic calculator. Surviving notes from Wilhelm Schickard in 1623 reveal that he designed and had built the earliest of the attempts at mechanizing calculation. A study of the surviving notes shows a machine that would have jammed after a few entries on the dial. Schickard abandoned his project in 1624 and never mentioned it again until his death years later in 1635. Two decades after Schickards supposedly failed attempt, in 1642, Blaise Pascal decisively solved these problems with his invention of the mechanical calculator. Co-opted into his fathers labour as tax collector in Rouen, Pascal designed the calculator to help in the amount of tedious arithmetic required. It was called Pascals Calculator or Pascaline, for forty years the arithmometer was the only type of mechanical calculator available for sale. The comptometer, introduced in 1887, was the first machine to use a keyboard which consisted of columns of nine keys for each digit, the Dalton adding machine, manufactured from 1902, was the first to have a 10 key keyboard. Electric motors were used on some mechanical calculators from 1901, the production of mechanical calculators came to a stop in the middle of the 1970s closing an industry that had lasted for 120 years. The first one was a mechanical calculator, his difference engine. In 1855, Georg Scheutz became the first of a handful of designers to succeed at building a smaller and simpler model of his difference engine, a crucial step was the adoption of a punched card system derived from the Jacquard loom making it infinitely programmable. The desire to economize time and mental effort in arithmetical computations and this instrument was probably invented by the Semitic races and later adopted in India, whence it spread westward throughout Europe and eastward to China and Japan. After the development of the abacus, no further advances were made until John Napier devised his numbering rods, or Napiers Bones, in 1617. The 17th century marked the beginning of the history of mechanical calculators, as it saw the invention of its first machines, including Pascals calculator, Blaise Pascal invented a mechanical calculator with a sophisticated carry mechanism in 1642. After three years of effort and 50 prototypes he introduced his calculator to the public and he built twenty of these machines in the following ten years. This machine could add and subtract two numbers directly and multiply and divide by repetition and this suggests that the carry mechanism would have proved itself in practice many times over. Pascals invention of the machine, just three hundred years ago, was made while he was a youth of nineteen
2.
Liquid-crystal display
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A liquid-crystal display is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals. Liquid crystals do not emit light directly, instead using a backlight or reflector to produce images in color or monochrome and they use the same basic technology, except that arbitrary images are made up of a large number of small pixels, while other displays have larger elements. LCDs are used in a range of applications including computer monitors, televisions, instrument panels, aircraft cockpit displays. Small LCD screens are common in consumer devices such as digital cameras, watches, calculators. LCD screens are used on consumer electronics products such as DVD players, video game devices. LCD screens have replaced heavy, bulky cathode ray tube displays in all applications. LCD screens are available in a range of screen sizes than CRT and plasma displays, with LCD screens available in sizes ranging from tiny digital watches to huge. Since LCD screens do not use phosphors, they do not suffer image burn-in when an image is displayed on a screen for a long time. LCDs are, however, susceptible to image persistence, the LCD screen is more energy-efficient and can be disposed of more safely than a CRT can. Its low electrical power consumption enables it to be used in battery-powered electronic equipment more efficiently than CRTs can be, by 2008, annual sales of televisions with LCD screens exceeded sales of CRT units worldwide, and the CRT became obsolete for most purposes. Without the liquid crystal between the filters, light passing through the first filter would be blocked by the second polarizer. Before an electric field is applied, the orientation of the molecules is determined by the alignment at the surfaces of electrodes. In a twisted nematic device, the surface alignment directions at the two electrodes are perpendicular to other, and so the molecules arrange themselves in a helical structure. This induces the rotation of the polarization of the incident light, and this light will then be mainly polarized perpendicular to the second filter, and thus be blocked and the pixel will appear black. By controlling the voltage applied across the liquid crystal layer in each pixel, color LCD systems use the same technique, with color filters used to generate red, green, and blue pixels. The optical effect of a TN device in the state is far less dependent on variations in the device thickness than that in the voltage-off state. Because of this, TN displays with low content and no backlighting are usually operated between crossed polarizers such that they appear bright with no voltage. When no image is displayed, different arrangements are used, for this purpose, TN LCDs are operated between parallel polarizers, whereas IPS LCDs feature crossed polarizers
3.
Seven-segment display
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A seven-segment display, or seven-segment indicator, is a form of electronic display device for displaying decimal numerals that is an alternative to the more complex dot matrix displays. Seven-segment displays are used in digital clocks, electronic meters, basic calculators. The seven elements of the display can be lit in different combinations to represent the arabic numerals, often the seven segments are arranged in an oblique arrangement, which aids readability. The numerals 6 and 9 may be represented by two different glyphs on seven-segment displays, with or without a tail, the seven segments are arranged as a rectangle of two vertical segments on each side with one horizontal segment on the top, middle, and bottom. Additionally, the seventh segment bisects the rectangle horizontally, there are also fourteen-segment displays and sixteen-segment displays, however, these have mostly been replaced by dot matrix displays. Twenty-two segment displays capable of displaying the full ASCII character set were available in the early 1980s. The segments of a 7-segment display are referred to by the letters A to G, for gasoline price totems and other large signs, vane displays made up of electromagnetically flipped light-reflecting segments are still commonly used. An alternative to the 7-segment display in the 1950s through the 1970s was the cold-cathode, starting in 1970, RCA sold a display device known as the Numitron that used incandescent filaments arranged into a seven-segment display. Integrated displays also exist, with single or multiple digits, some of these integrated displays incorporate their own internal decoder, though most do not, each individual LED is brought out to a connecting pin as described. Multiple-digit LED displays as used in calculators and similar devices used multiplexed displays to reduce the number of I/O pins required to control the display. For example, all the anodes of the A segments of each digit position would be connected together and to a driver circuit pin, while the cathodes of all segments for each digit would be connected. In this manner an eight digit display with seven segments and a point would require only 8 cathode drivers and 8 anode drivers, instead of sixty-four drivers. A single byte can encode the full state of a 7-segment-display, the most popular bit encodings are gfedcba and abcdefg, where each letter represents a particular segment in the display. In the gfedcba representation, a value of 0x06 would turn on segments c and b. In 1908, F. W. Wood invented an 8-segment display, in 1910, a seven-segment display illuminated by incandescent bulbs was used on a power-plant boiler room signal panel. They were also used to show the dialed telephone number to operators during the transition from manual to automatic telephone dialing and they did not achieve widespread use until the advent of LEDs in the 1970s. For many applications, dot-matrix LCDs have largely superseded LED displays, unlike LEDs, the shapes of elements in an LCD panel are arbitrary since they are formed on the display by a kind of printing process. The seven-segment display has inspired designers to produce typefaces reminiscent of that display, such as New Alphabet, DB LCD Temp, ION B
4.
Dot matrix
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A dot matrix is a 2-dimensional patterned array, used to represent characters, symbols and images. Every type of modern technology uses dot matrices for display of information, including phones, televisions. They are also used in textiles with sewing, knitting, in printers, the dots are usually the darkened areas of the paper. In displays, the dots may light up, as in an LED, CRT, or plasma display, or darken, as in an LCD. As an impact printer, the term refers to low-resolution impact printers, with a column of 8,9 or 24 pins hitting an ink-impregnated fabric ribbon, like a typewriter ribbon. It was originally contrasted with both daisy wheel printers and line printers that used fixed-shape embossed metal or plastic stamps to mark paper. Impact printers survive where multi-part forms are needed, as the pins can impress dots through multiple layers of paper to make a carbonless copy, all types of electronic printers typically generate image data as a two-step process. External raster image processing was possible such as to print a graphical image, depending on the printer technology the dot size or grid shape may not be uniform. Some printers are capable of producing smaller dots and will intermesh the small dots within the larger ones for antialiasing. A dot matrix is useful for marking materials other than paper, in manufacturing industry, many product marking applications use dot matrix inkjet or impact methods. This can also be used to print 2D matrix codes, e. g. Datamatrix. Although the output of modern computers is generally all in the form of dot matrices, vector data encoding requires less memory and less data storage, in situations where the shapes may need to be resized, as with font typefaces. For maximum image quality using only dot matrix fonts, it would be necessary to store a separate dot matrix pattern for the different potential point sizes that might be used. Instead, a group of vector shapes is used to render all the specific dot matrix patterns needed for the current display or printing task. An LED matrix or LED display is a large, low-resolution form of dot-matrix display and it consists of a 2-D diode matrix with their cathodes joined in rows and their anodes joined in columns. By controlling the flow of electricity through each row and column pair it is possible to control each LED individually, by multiplexing, scanning across rows, quickly flashing the LEDs on and off, it is possible to create characters or pictures to display information to the user. By varying the rate per LED, the display can approximate levels of brightness. Multi-colored LEDs or RGB-colored LEDs permit use as an image display
5.
Electronics
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Electronics is the science of controlling electrical energy electrically, in which the electrons have a fundamental role. Commonly, electronic devices contain circuitry consisting primarily or exclusively of active semiconductors supplemented with passive elements, the science of electronics is also considered to be a branch of physics and electrical engineering. The ability of electronic devices to act as switches makes digital information processing possible, until 1950 this field was called radio technology because its principal application was the design and theory of radio transmitters, receivers, and vacuum tubes. Today, most electronic devices use semiconductor components to perform electron control and this article focuses on engineering aspects of electronics. Components are generally intended to be connected together, usually by being soldered to a circuit board. Components may be packaged singly, or in more complex groups as integrated circuits, some common electronic components are capacitors, inductors, resistors, diodes, transistors, etc. Components are often categorized as active or passive, vacuum tubes were among the earliest electronic components. They were almost solely responsible for the revolution of the first half of the Twentieth Century. They took electronics from parlor tricks and gave us radio, television, phonographs, radar, long distance telephony and they played a leading role in the field of microwave and high power transmission as well as television receivers until the middle of the 1980s. Since that time, solid state devices have all but completely taken over, vacuum tubes are still used in some specialist applications such as high power RF amplifiers, cathode ray tubes, specialist audio equipment, guitar amplifiers and some microwave devices. The 608 contained more than 3,000 germanium transistors, thomas J. Watson Jr. ordered all future IBM products to use transistors in their design. From that time on transistors were almost exclusively used for computer logic, circuits and components can be divided into two groups, analog and digital. A particular device may consist of circuitry that has one or the other or a mix of the two types, most analog electronic appliances, such as radio receivers, are constructed from combinations of a few types of basic circuits. Analog circuits use a range of voltage or current as opposed to discrete levels as in digital circuits. The number of different analog circuits so far devised is huge, especially because a circuit can be defined as anything from a single component, analog circuits are sometimes called linear circuits although many non-linear effects are used in analog circuits such as mixers, modulators, etc. Good examples of analog circuits include vacuum tube and transistor amplifiers, one rarely finds modern circuits that are entirely analog. These days analog circuitry may use digital or even microprocessor techniques to improve performance and this type of circuit is usually called mixed signal rather than analog or digital. Sometimes it may be difficult to differentiate between analog and digital circuits as they have elements of both linear and non-linear operation, an example is the comparator which takes in a continuous range of voltage but only outputs one of two levels as in a digital circuit
6.
Arithmetic
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Arithmetic is a branch of mathematics that consists of the study of numbers, especially the properties of the traditional operations between them—addition, subtraction, multiplication and division. Arithmetic is an part of number theory, and number theory is considered to be one of the top-level divisions of modern mathematics, along with algebra, geometry. The terms arithmetic and higher arithmetic were used until the beginning of the 20th century as synonyms for number theory and are still used to refer to a wider part of number theory. The earliest written records indicate the Egyptians and Babylonians used all the elementary arithmetic operations as early as 2000 BC and these artifacts do not always reveal the specific process used for solving problems, but the characteristics of the particular numeral system strongly influence the complexity of the methods. The hieroglyphic system for Egyptian numerals, like the later Roman numerals, in both cases, this origin resulted in values that used a decimal base but did not include positional notation. Complex calculations with Roman numerals required the assistance of a board or the Roman abacus to obtain the results. Early number systems that included positional notation were not decimal, including the system for Babylonian numerals. Because of this concept, the ability to reuse the same digits for different values contributed to simpler. The continuous historical development of modern arithmetic starts with the Hellenistic civilization of ancient Greece, prior to the works of Euclid around 300 BC, Greek studies in mathematics overlapped with philosophical and mystical beliefs. For example, Nicomachus summarized the viewpoint of the earlier Pythagorean approach to numbers, Greek numerals were used by Archimedes, Diophantus and others in a positional notation not very different from ours. Because the ancient Greeks lacked a symbol for zero, they used three separate sets of symbols, one set for the units place, one for the tens place, and one for the hundreds. Then for the place they would reuse the symbols for the units place. Their addition algorithm was identical to ours, and their multiplication algorithm was very slightly different. Their long division algorithm was the same, and the square root algorithm that was taught in school was known to Archimedes. He preferred it to Heros method of successive approximation because, once computed, a digit doesnt change, and the square roots of perfect squares, such as 7485696, terminate immediately as 2736. For numbers with a part, such as 546.934. The ancient Chinese used a positional notation. Because they also lacked a symbol for zero, they had one set of symbols for the place
7.
Mathematics
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Mathematics is the study of topics such as quantity, structure, space, and change. There is a range of views among mathematicians and philosophers as to the exact scope, Mathematicians seek out patterns and use them to formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proof, when mathematical structures are good models of real phenomena, then mathematical reasoning can provide insight or predictions about nature. Through the use of abstraction and logic, mathematics developed from counting, calculation, measurement, practical mathematics has been a human activity from as far back as written records exist. The research required to solve mathematical problems can take years or even centuries of sustained inquiry, rigorous arguments first appeared in Greek mathematics, most notably in Euclids Elements. Galileo Galilei said, The universe cannot be read until we have learned the language and it is written in mathematical language, and the letters are triangles, circles and other geometrical figures, without which means it is humanly impossible to comprehend a single word. Without these, one is wandering about in a dark labyrinth, carl Friedrich Gauss referred to mathematics as the Queen of the Sciences. Benjamin Peirce called mathematics the science that draws necessary conclusions, David Hilbert said of mathematics, We are not speaking here of arbitrariness in any sense. Mathematics is not like a game whose tasks are determined by arbitrarily stipulated rules, rather, it is a conceptual system possessing internal necessity that can only be so and by no means otherwise. Albert Einstein stated that as far as the laws of mathematics refer to reality, they are not certain, Mathematics is essential in many fields, including natural science, engineering, medicine, finance and the social sciences. Applied mathematics has led to entirely new mathematical disciplines, such as statistics, Mathematicians also engage in pure mathematics, or mathematics for its own sake, without having any application in mind. There is no clear line separating pure and applied mathematics, the history of mathematics can be seen as an ever-increasing series of abstractions. The earliest uses of mathematics were in trading, land measurement, painting and weaving patterns, in Babylonian mathematics elementary arithmetic first appears in the archaeological record. Numeracy pre-dated writing and numeral systems have many and diverse. Between 600 and 300 BC the Ancient Greeks began a study of mathematics in its own right with Greek mathematics. Mathematics has since been extended, and there has been a fruitful interaction between mathematics and science, to the benefit of both. Mathematical discoveries continue to be made today, the overwhelming majority of works in this ocean contain new mathematical theorems and their proofs. The word máthēma is derived from μανθάνω, while the modern Greek equivalent is μαθαίνω, in Greece, the word for mathematics came to have the narrower and more technical meaning mathematical study even in Classical times
8.
Intel 4004
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The Intel 4004 is a 4-bit central processing unit released by Intel Corporation in 1971. It was the first commercially available microprocessor by Intel, the chip design started in April 1970, when Federico Faggin joined Intel, and it was completed under his leadership in January 1971. The first commercial sale of the fully operational 4004 occurred in March 1971 to Busicom Corp. of Japan for which it was originally designed and built as a custom chip. In mid-November of the year, with the prophetic ad Announcing a new era in integrated electronics. The 4004 is history’s first monolithic CPU, fully integrated in one small chip, the 4004 microprocessor is one of 4 chips constituting the MCS-4 chip-set, which includes the 4001 ROM,4002 RAM, and 4003 Shift Register. With these components, small computers with varying amounts of memory, both the AL1 and the MP944 use several chips for the implementation of the CPU function. The TMS0100 chip was presented as a “calculator on a chip” with the original designation TMS1802NC and this chip contains a very primitive CPU and can only be used to implement various simple 4-function calculators. It is the precursor of the TMS1000, introduced in 1974, which is considered the first microcontroller i. e. a computer on a chip containing not only the CPU, but also ROM, RAM, and I/O functions. The MCS-4 was eventually superseded by powerful microcontrollers like the Intel 8048, the architecture of this processor formed the basis for later models of microprocessors. The first public mention of 4004 was an advertisement in the November 15,1971 edition of Electronic News, Faggin, the sole chip designer among the engineers on the MCS-4 project, was the only one with experience in metal-oxide semiconductor random logic and circuit design. He also had the knowledge of the new silicon gate process technology with self-aligned gates. At Fairchild in 1968, Faggin also designed and manufactured the worlds first commercial IC using SGT and his methodology set the design style for all the early Intel microprocessors and later for the Zilog Z80. He also led the MCS-4 project and was responsible for its successful outcome, Marcian Ted Hoff, head of the Application Research Department, contributed the architectural proposal for Busicom working with Stanley Mazor in 1969, then he moved on to other projects. Shima designed the Busicom calculator firmware and assisted Faggin during the first six months of the implementation, the manager of Intels MOS Design Department was Leslie L. Vadász. using Intel’s newly developed dynamic RAM memory. This resulted in the 4004 architecture, which is part of a family of chips, including ROM, DRAM and it was not until the development of the 40-pin 8080 in 1974 that the address and data buses would be separated, giving faster and simpler access to memory. The original clock rate design goal was 1 MHz, the same as the IBM1620 Model I. The Intel 4004 was designed by cutting sheets of Rubylith into thin strips to lay out the circuits to be printed. For the purpose of testing the produced chips, Faggin developed a tester for silicon waffers of MCS-4 family that was driven by 4004 chip
9.
Microprocessor
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A microprocessor is a computer processor which incorporates the functions of a computers central processing unit on a single integrated circuit, or at most a few integrated circuits. Microprocessors contain both combinational logic and sequential digital logic, Microprocessors operate on numbers and symbols represented in the binary numeral system. The integration of a whole CPU onto a chip or on a few chips greatly reduced the cost of processing power. Integrated circuit processors are produced in numbers by highly automated processes resulting in a low per unit cost. Single-chip processors increase reliability as there are many electrical connections to fail. As microprocessor designs get better, the cost of manufacturing a chip generally stays the same, before microprocessors, small computers had been built using racks of circuit boards with many medium- and small-scale integrated circuits. Microprocessors combined this into one or a few large-scale ICs, the internal arrangement of a microprocessor varies depending on the age of the design and the intended purposes of the microprocessor. Advancing technology makes more complex and powerful chips feasible to manufacture, a minimal hypothetical microprocessor might only include an arithmetic logic unit and a control logic section. The ALU performs operations such as addition, subtraction, and operations such as AND or OR, each operation of the ALU sets one or more flags in a status register, which indicate the results of the last operation. The control logic retrieves instruction codes from memory and initiates the sequence of operations required for the ALU to carry out the instruction, a single operation code might affect many individual data paths, registers, and other elements of the processor. As integrated circuit technology advanced, it was feasible to manufacture more and more complex processors on a single chip, the size of data objects became larger, allowing more transistors on a chip allowed word sizes to increase from 4- and 8-bit words up to todays 64-bit words. Additional features were added to the architecture, more on-chip registers sped up programs. Floating-point arithmetic, for example, was not available on 8-bit microprocessors. Integration of the point unit first as a separate integrated circuit and then as part of the same microprocessor chip. Occasionally, physical limitations of integrated circuits made such practices as a bit slice approach necessary, instead of processing all of a long word on one integrated circuit, multiple circuits in parallel processed subsets of each data word. With the ability to put large numbers of transistors on one chip and this CPU cache has the advantage of faster access than off-chip memory, and increases the processing speed of the system for many applications. Processor clock frequency has increased more rapidly than external memory speed, except in the recent past, a microprocessor is a general purpose system. Several specialized processing devices have followed from the technology, A digital signal processor is specialized for signal processing, graphics processing units are processors designed primarily for realtime rendering of 3D images
10.
Intel
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Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California that was founded by Gordon Moore and Robert Noyce. It is the worlds largest and highest valued semiconductor chip makers based on revenue, and is the inventor of the x86 series of microprocessors, Intel supplies processors for computer system manufacturers such as Apple, Lenovo, HP, and Dell. Intel Corporation was founded on July 18,1968, by semiconductor pioneers Robert Noyce and Gordon Moore, the companys name was conceived as portmanteau of the words integrated and electronics. The fact that intel is the term for intelligence information made the name appropriate. Intel was a developer of SRAM and DRAM memory chips. Although Intel created the worlds first commercial microprocessor chip in 1971, during the 1990s, Intel invested heavily in new microprocessor designs fostering the rapid growth of the computer industry. The Open Source Technology Center at Intel hosts PowerTOP and LatencyTOP, and supports other projects such as Wayland, Intel Array Building Blocks, and Threading Building Blocks. Client Computing Group – 55% of 2016 revenues – produces hardware components used in desktop, data Center Group – 29% of 2016 revenues – produces hardware components used in server, network, and storage platforms. Internet of Things Group – 5% of 2016 revenues – offers platforms designed for retail, transportation, industrial, buildings, non-Volatile Memory Solutions Group – 4% of 2016 revenues – manufactures NAND flash memory products primarily used in solid-state drives. Intel Security Group – 4% of 2016 revenues – produces software, particularly security, programmable Solutions Group – 3% of 2016 revenues – manufactures programmable semiconductors. In 2016, Dell accounted for 15% of Intels total revenues, Lenovo accounted for 13% of total revenues, in the 1980s, Intel was among the top ten sellers of semiconductors in the world. In 1991, Intel became the biggest chip maker by revenue and has held the position ever since, other top semiconductor companies include TSMC, Advanced Micro Devices, Samsung, Texas Instruments, Toshiba and STMicroelectronics. Competitors in PC chip sets include Advanced Micro Devices, VIA Technologies, Silicon Integrated Systems, however, the cross-licensing agreement is canceled in the event of an AMD bankruptcy or takeover. Some smaller competitors such as VIA Technologies produce low-power x86 processors for small factor computers, however, the advent of such mobile computing devices, in particular, smartphones, has in recent years led to a decline in PC sales. Since over 95% of the worlds smartphones currently use processors designed by ARM Holdings, ARM is also planning to make inroads into the PC and server market. Intel has been involved in disputes regarding violation of antitrust laws. Intel was founded in Mountain View, California in 1968 by Gordon E. Moore, a chemist, and Robert Noyce, arthur Rock helped them find investors, while Max Palevsky was on the board from an early stage. Moore and Noyce had left Fairchild Semiconductor to found Intel, Rock was not an employee, but he was an investor and was chairman of the board
11.
Busicom
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Busicom was a Japanese company that owned the rights to Intels first microprocessor, the Intel 4004, which they created in partnership with Intel in 1970. Busicom asked Intel to design a set of integrated circuits for a new line of electronic calculators in 1969. In doing this, they spurred the invention of Intels first microprocessor to be commercialized, Busicom owned the exclusive rights to the design and its components in 1970 but shared them with Intel in 1971. Two companies have done business as Busicom over the years, the Nippon Calculating Machine Corp, Ltd, the Nippon Calculating Machine Corp was incorporated in 1945 and changed its name in 1967 to Business Computer Corporation, Busicom. Due to a recession in Japan in 1974, Busicom became the first major Japanese company in the industry to fail. Originally, they made Odhner type mechanical calculators and then moved on to electronic calculators always using state of the art designs, one of their last mechanical calculators is the HL-21, an Odhner type machine. Their first calculator with a microprocessor is the Busicom 141-PF and their entry based calculators, the Busicom LE-120A and LE-120S, were the first to fit in a pocket and also the first calculators to use an LED display. People who were influential in convinicing Busicom to switch to using microprocessors were Tadashi Sasaki, busicoms management agreed to Hoffs new approach and the chips implementation was led by Federico Faggin who had previously developed the Silicon Gate Technology at Fairchild Semiconductor. It was this technology made possible the design of the microprocessor. The 4 ICs were delivered to Busicom in January 1971, in mid-1971 Busicom, which had exclusive right to the design and its components, asked Intel to lower their prices. Intel renegotiated their contract and Busicom gave up its rights to the chips. A few months later, on November 15,1971, Intel announced the availability of the first microprocessor chipset family. Broughtons of Bristol is a company selling and maintaining a line of business machines. They used to buy most of their equipment from Busicom and bought their trade name when they went bankrupt in 1974
12.
Petroleum industry
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The petroleum industry includes the global processes of exploration, extraction, refining, transporting, and marketing of petroleum products. The largest volume products of the industry are fuel oil and gasoline, Petroleum is also the raw material for many chemical products, including pharmaceuticals, solvents, fertilizers, pesticides, synthetic fragrances, and plastics. The industry is divided into three major components, upstream, midstream and downstream. Midstream operations are included in the downstream category. Petroleum is vital to many industries, and is of importance to the maintenance of industrial civilization in its current configuration, and thus is a critical concern for many nations. Oil accounts for a percentage of the world’s energy consumption, ranging from a low of 32% for Europe and Asia. Other geographic regions consumption patterns are as follows, South and Central America, Africa, the world consumes 30 billion barrels of oil per year, with developed nations being the largest consumers. The United States consumed 25% of the oil produced in 2007, the production, distribution, refining, and retailing of petroleum taken as a whole represents the worlds largest industry in terms of dollar value. Petroleum is a naturally occurring liquid found in rock formations and it consists of a complex mixture of hydrocarbons of various molecular weights, plus other organic compounds. It is generally accepted that oil is formed mostly from the carbon rich remains of ancient plankton after exposure to heat, Petroleum in an unrefined state has been utilized by humans for over 5000 years. Oil in general has been used since early history to keep fires ablaze. Its importance to the world economy evolved slowly, with oil used for lighting in the 19th century and wood. The Industrial Revolution generated an increasing need for energy which was met mainly by coal, Imperial Russia produced 3,500 tons of oil in 1825 and doubled its output by mid-century. Batum is renamed to Batumi in 1936, at the turn of the 20th century, Imperial Russias output of oil, almost entirely from the Apsheron Peninsula, accounted for half of the worlds production and dominated international markets. Nearly 200 small refineries operated in the suburbs of Baku by 1884, as a side effect of these early developments, the Apsheron Peninsula emerged as the worlds oldest legacy of oil pollution and environmental negligence. In 1846, Baku the first ever well drilled with percussion tools to a depth of 21 meters for oil exploration, in 1878, Ludvig Nobel and his Branobel company revolutionized oil transport by commissioning the first oil tanker and launching it on the Caspian Sea. Samuel Kier established Americas first oil refinery in Pittsburgh on Seventh avenue near Grant Street, one of the first modern oil refineries were built by Ignacy Łukasiewicz near Jasło, Poland in 1854–56. These were initially small as demand for refined fuel was limited, the refined products were used in artificial asphalt, machine oil and lubricants, in addition to Łukasiewiczs kerosene lamp
13.
ISO/IEC 7810
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ISO/IEC7810 Identification cards — Physical characteristics is an international standard that defines the physical characteristics for identification cards. The characteristics specified include, Physical dimensions Resistance to bending, flame, chemicals, temperature, the standard defines four card sizes, ID-1, ID-2, ID-3 and ID-000. All card sizes have a thickness of 0.76 mm. The standard defines both metric and imperial measurements, noting that, The ID-1 format specifies a size of 85.60 ×53.98 mm and it is commonly used for banking cards. Today it is used for driving licences in many countries. Both the recently issued Irish and much older U. S. passport cards, Crew Member Certificates, the ID-2 format specifies a size of 105 ×74 mm. This size is the A7 format, the ID-2 format is used, for example, for visas. It is used for the French identity card, and was used by the German identity card issued until October 2010. Since November 2010, German ID cards are issued in the ID-1 format more widely used in Europe for national ID cards and it was previously also used for Finnish and Swedish drivers licences before those changed to the ID-1 format. ID-3 specifies a size of 125 ×88 mm and this size is the B7 format. This format is used for passport booklets. ID-000 specifies a size of 25 mm ×15 mm, with one corner slightly bevelled, the ID-000 size was first defined by ENV 1375-1, Identification card systems — Intersector integrated circuit card additional formats — Part 1, ID-000 card size and physical characteristics. This size is used for the format of subscriber identity modules. An ID-1 size card containing an ID-000 size card is denoted as ID-1/000, iSO/IEC7816 defines ID-1 identification cards with an embedded chip and contact surfaces for power, clock, reset and serial-data signals. Magnetic stripe card MM Code IEC7810, 2003-1
14.
Integrated circuit
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An integrated circuit or monolithic integrated circuit is a set of electronic circuits on one small flat piece of semiconductor material, normally silicon. The ICs mass production capability, reliability and building-block approach to circuit design ensured the rapid adoption of standardized ICs in place of using discrete transistors. ICs are now used in all electronic equipment and have revolutionized the world of electronics. Computers, mobile phones, and other home appliances are now inextricable parts of the structure of modern societies, made possible by the small size. These advances, roughly following Moores law, allow a computer chip of 2016 to have millions of times the capacity, ICs have two main advantages over discrete circuits, cost and performance. Cost is low because the chips, with all their components, are printed as a unit by photolithography rather than being constructed one transistor at a time, furthermore, packaged ICs use much less material than discrete circuits. Performance is high because the ICs components switch quickly and consume little power because of their small size, the main disadvantage of ICs is the high cost to design them and fabricate the required photomasks. This high initial cost means ICs are only practical when high production volumes are anticipated, Circuits meeting this definition can be constructed using many different technologies, including thin-film transistor, thick film technology, or hybrid integrated circuit. However, in general usage integrated circuit has come to refer to the single-piece circuit construction originally known as a integrated circuit. Jacobi disclosed small and cheap hearing aids as typical industrial applications of his patent, an immediate commercial use of his patent has not been reported. The idea of the circuit was conceived by Geoffrey Dummer. Dummer presented the idea to the public at the Symposium on Progress in Quality Electronic Components in Washington and he gave many symposia publicly to propagate his ideas, and unsuccessfully attempted to build such a circuit in 1956. A precursor idea to the IC was to create small ceramic squares, Components could then be integrated and wired into a bidimensional or tridimensional compact grid. This idea, which seemed very promising in 1957, was proposed to the US Army by Jack Kilby, however, as the project was gaining momentum, Kilby came up with a new, revolutionary design, the IC. In his patent application of 6 February 1959, Kilby described his new device as a body of semiconductor material … wherein all the components of the circuit are completely integrated. The first customer for the new invention was the US Air Force, Kilby won the 2000 Nobel Prize in Physics for his part in the invention of the integrated circuit. His work was named an IEEE Milestone in 2009, half a year after Kilby, Robert Noyce at Fairchild Semiconductor developed his own idea of an integrated circuit that solved many practical problems Kilbys had not. Noyces design was made of silicon, whereas Kilbys chip was made of germanium, Noyce credited Kurt Lehovec of Sprague Electric for the principle of p–n junction isolation, a key concept behind the IC
15.
Operating system
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An operating system is system software that manages computer hardware and software resources and provides common services for computer programs. All computer programs, excluding firmware, require a system to function. Operating systems are found on many devices that contain a computer – from cellular phones, the dominant desktop operating system is Microsoft Windows with a market share of around 83. 3%. MacOS by Apple Inc. is in place, and the varieties of Linux is in third position. Linux distributions are dominant in the server and supercomputing sectors, other specialized classes of operating systems, such as embedded and real-time systems, exist for many applications. A single-tasking system can run one program at a time. Multi-tasking may be characterized in preemptive and co-operative types, in preemptive multitasking, the operating system slices the CPU time and dedicates a slot to each of the programs. Unix-like operating systems, e. g. Solaris, Linux, cooperative multitasking is achieved by relying on each process to provide time to the other processes in a defined manner. 16-bit versions of Microsoft Windows used cooperative multi-tasking, 32-bit versions of both Windows NT and Win9x, used preemptive multi-tasking. Single-user operating systems have no facilities to distinguish users, but may allow multiple programs to run in tandem, a distributed operating system manages a group of distinct computers and makes them appear to be a single computer. The development of networked computers that could be linked and communicate with each other gave rise to distributed computing, distributed computations are carried out on more than one machine. When computers in a work in cooperation, they form a distributed system. The technique is used both in virtualization and cloud computing management, and is common in large server warehouses, embedded operating systems are designed to be used in embedded computer systems. They are designed to operate on small machines like PDAs with less autonomy and they are able to operate with a limited number of resources. They are very compact and extremely efficient by design, Windows CE and Minix 3 are some examples of embedded operating systems. A real-time operating system is a system that guarantees to process events or data by a specific moment in time. A real-time operating system may be single- or multi-tasking, but when multitasking, early computers were built to perform a series of single tasks, like a calculator. Basic operating system features were developed in the 1950s, such as resident monitor functions that could run different programs in succession to speed up processing
16.
Ancient UNIX
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After the publication of the Lions book, work was undertaken to release the earlier versions of the codebase. SCO first released the code under an educational license. Version 6 Unix provided the basis for the MIT xv6 teaching system, which is an update of that version to ANSI C and the x86 platform. As an example of how relicensing the old Unix code bases has affected the modern computing community, therefore, traditional vi could not be distributed freely, and various work-alikes were created. Now that this code is no longer encumbered, the traditional vi has been adapted for modern Unix-like operating systems. The Unix Heritage Society, a dedicated to the preservation and maintenance of historical UNIX systems code, disk images
17.
Computer program
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A computer program is a collection of instructions that performs a specific task when executed by a computer. A computer requires programs to function, and typically executes the programs instructions in a processing unit. A computer program is written by a computer programmer in a programming language. From the program in its form of source code, a compiler can derive machine code—a form consisting of instructions that the computer can directly execute. Alternatively, a program may be executed with the aid of an interpreter. A part of a program that performs a well-defined task is known as an algorithm. A collection of programs, libraries and related data are referred to as software. Computer programs may be categorized along functional lines, such as software or system software. The earliest programmable machines preceded the invention of the digital computer, in 1801, Joseph-Marie Jacquard devised a loom that would weave a pattern by following a series of perforated cards. Patterns could be weaved and repeated by arranging the cards, in 1837, Charles Babbage was inspired by Jacquards loom to attempt to build the Analytical Engine. The names of the components of the device were borrowed from the textile industry. In the textile industry, yarn was brought from the store to be milled, the device would have had a store—memory to hold 1,000 numbers of 40 decimal digits each. Numbers from the store would then have then transferred to the mill. It was programmed using two sets of perforated cards—one to direct the operation and the other for the input variables, however, after more than 17,000 pounds of the British governments money, the thousands of cogged wheels and gears never fully worked together. During a nine-month period in 1842–43, Ada Lovelace translated the memoir of Italian mathematician Luigi Menabrea, the memoir covered the Analytical Engine. The translation contained Note G which completely detailed a method for calculating Bernoulli numbers using the Analytical Engine and this note is recognized by some historians as the worlds first written computer program. In 1936, Alan Turing introduced the Universal Turing machine—a theoretical device that can model every computation that can be performed on a Turing complete computing machine and it is a finite-state machine that has an infinitely long read/write tape. The machine can move the back and forth, changing its contents as it performs an algorithm
18.
Personal digital assistant
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A personal digital assistant, also known as a handheld PC, or personal data assistant, is a mobile device that functions as a personal information manager. PDAs were largely discontinued in the early 2010s after the adoption of highly capable smartphones, in particular those based on iOS. Nearly all PDAs have the ability to connect to the Internet, a PDA has an electronic visual display, letting it include a web browser. All models also have audio capabilities, allowing usage as a media player. Most PDAs can access the Internet, intranets or extranets via Wi-Fi or Wireless Wide Area Networks, the first PDA was released in 1984 by Psion, the Organizer, followed by Psions Series 3, in 1991. The latter began to resemble the more familiar PDA style, including a full keyboard, the term PDA was first used on January 7,1992 by Apple Computer CEO John Sculley at the Consumer Electronics Show in Las Vegas, Nevada, referring to the Apple Newton. In 1994, IBM introduced the first PDA with full mobile phone functionality, the IBM Simon, then in 1996, Nokia introduced a PDA with full mobile phone functionality, the 9000 Communicator, which became the worlds best-selling PDA. The Communicator spawned a new category of PDAs, the PDA phone, another early entrant in this market was Palm, with a line of PDA products which began in March 1996. A typical PDA has a touchscreen for entering data, a card slot for data storage. PDAs with wireless data connections also typically include an email client, many of the original PDAs, such as the Apple Newton and Palm Pilot, featured a touchscreen for user interaction, having only a few buttons—usually reserved for shortcuts to often-used programs. Some touchscreen PDAs, including Windows Mobile devices, had a stylus to facilitate making selections. The user interacts with the device by tapping the screen to select buttons or issue commands, typical methods of entering text on touchscreen PDAs include, A virtual keyboard, where a keyboard is shown on the touchscreen. Text is entered by tapping the on-screen keyboard with a finger or stylus, an external keyboard connected via USB, Infrared port, or Bluetooth. Some users may choose a chorded keyboard for one-handed use, handwriting recognition, where letters or words are written on the touchscreen, often with a stylus, and the PDA converts the input to text. Recognition and computation of handwritten horizontal and vertical formulas, such as 1 +2 =, stroke recognition allows the user to make a predefined set of strokes on the touchscreen, sometimes in a special input area, representing the various characters to be input. The strokes are often simplified character shapes, making them easier for the device to recognize, one widely known stroke recognition system is Palms Graffiti. Despite research and development projects, end-users experience mixed results with handwriting recognition systems, some find it frustrating and inaccurate, while others are satisfied with the quality of the recognition. Touchscreen PDAs intended for use, such as the BlackBerry and Palm Treo, usually also offer full keyboards and scroll wheels or thumbwheels to facilitate data entry
19.
Scientific calculator
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A scientific calculator is a type of electronic calculator, usually but not always handheld, designed to calculate problems in science, engineering, and mathematics. They have almost completely replaced slide rules in almost all traditional applications, there is also some overlap with the financial calculator market. A few have multi-line displays, with recent models from Hewlett-Packard, Texas Instruments, Casio, Sharp. By providing a method to enter an entire problem in as it is written on the page using simple formatting tools, the HP-35, introduced on February 1,1972, was Hewlett-Packards first pocket calculator and the worlds first handheld scientific calculator. Like some of HPs desktop calculators it used RPN, introduced at US$395, the HP-35 was available from 1972 to 1975. Texas Instruments, after the introduction of units with scientific notation, came out with a handheld scientific calculator on January 15,1974. TI continues to be a player in the calculator market. Casio and Sharp have also been major players, with Casios fx series being a common brand. Casio is also a player in the graphing calculator market
20.
Trigonometry
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Trigonometry is a branch of mathematics that studies relationships involving lengths and angles of triangles. The field emerged in the Hellenistic world during the 3rd century BC from applications of geometry to astronomical studies, Trigonometry is also the foundation of surveying. Trigonometry is most simply associated with planar right-angle triangles, thus the majority of applications relate to right-angle triangles. One exception to this is spherical trigonometry, the study of triangles on spheres, surfaces of constant positive curvature, Trigonometry on surfaces of negative curvature is part of hyperbolic geometry. Trigonometry basics are often taught in schools, either as a course or as a part of a precalculus course. Sumerian astronomers studied angle measure, using a division of circles into 360 degrees, the ancient Nubians used a similar method. In 140 BC, Hipparchus gave the first tables of chords, analogous to modern tables of sine values, in the 2nd century AD, the Greco-Egyptian astronomer Ptolemy printed detailed trigonometric tables in Book 1, chapter 11 of his Almagest. Ptolemy used chord length to define his trigonometric functions, a difference from the sine convention we use today. The modern sine convention is first attested in the Surya Siddhanta and these Greek and Indian works were translated and expanded by medieval Islamic mathematicians. By the 10th century, Islamic mathematicians were using all six trigonometric functions, had tabulated their values, at about the same time, Chinese mathematicians developed trigonometry independently, although it was not a major field of study for them. At the same time, another translation of the Almagest from Greek into Latin was completed by the Cretan George of Trebizond, Trigonometry was still so little known in 16th-century northern Europe that Nicolaus Copernicus devoted two chapters of De revolutionibus orbium coelestium to explain its basic concepts. Driven by the demands of navigation and the growing need for maps of large geographic areas. Bartholomaeus Pitiscus was the first to use the word, publishing his Trigonometria in 1595, gemma Frisius described for the first time the method of triangulation still used today in surveying. It was Leonhard Euler who fully incorporated complex numbers into trigonometry, the works of the Scottish mathematicians James Gregory in the 17th century and Colin Maclaurin in the 18th century were influential in the development of trigonometric series. Also in the 18th century, Brook Taylor defined the general Taylor series, if one angle of a triangle is 90 degrees and one of the other angles is known, the third is thereby fixed, because the three angles of any triangle add up to 180 degrees. The two acute angles therefore add up to 90 degrees, they are complementary angles, the shape of a triangle is completely determined, except for similarity, by the angles. Once the angles are known, the ratios of the sides are determined, if the length of one of the sides is known, the other two are determined. Sin A = opposite hypotenuse = a c, Cosine function, defined as the ratio of the adjacent leg to the hypotenuse
21.
Statistics
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Statistics is a branch of mathematics dealing with the collection, analysis, interpretation, presentation, and organization of data. In applying statistics to, e. g. a scientific, industrial, or social problem, populations can be diverse topics such as all people living in a country or every atom composing a crystal. Statistics deals with all aspects of data including the planning of data collection in terms of the design of surveys, statistician Sir Arthur Lyon Bowley defines statistics as Numerical statements of facts in any department of inquiry placed in relation to each other. When census data cannot be collected, statisticians collect data by developing specific experiment designs, representative sampling assures that inferences and conclusions can safely extend from the sample to the population as a whole. In contrast, an observational study does not involve experimental manipulation, inferences on mathematical statistics are made under the framework of probability theory, which deals with the analysis of random phenomena. A standard statistical procedure involves the test of the relationship between two data sets, or a data set and a synthetic data drawn from idealized model. A hypothesis is proposed for the relationship between the two data sets, and this is compared as an alternative to an idealized null hypothesis of no relationship between two data sets. Rejecting or disproving the hypothesis is done using statistical tests that quantify the sense in which the null can be proven false. Working from a hypothesis, two basic forms of error are recognized, Type I errors and Type II errors. Multiple problems have come to be associated with this framework, ranging from obtaining a sufficient sample size to specifying an adequate null hypothesis, measurement processes that generate statistical data are also subject to error. Many of these errors are classified as random or systematic, the presence of missing data or censoring may result in biased estimates and specific techniques have been developed to address these problems. Statistics continues to be an area of research, for example on the problem of how to analyze Big data. Statistics is a body of science that pertains to the collection, analysis, interpretation or explanation. Some consider statistics to be a mathematical science rather than a branch of mathematics. While many scientific investigations make use of data, statistics is concerned with the use of data in the context of uncertainty, mathematical techniques used for this include mathematical analysis, linear algebra, stochastic analysis, differential equations, and measure-theoretic probability theory. In applying statistics to a problem, it is practice to start with a population or process to be studied. Populations can be diverse topics such as all living in a country or every atom composing a crystal. Ideally, statisticians compile data about the entire population and this may be organized by governmental statistical institutes
22.
Graphing calculator
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A graphing calculator is a handheld calculator that is capable of plotting graphs, solving simultaneous equations, and performing other tasks with variables. Most popular graphing calculators are also programmable, allowing the user to create customized programs, typically for scientific/engineering, because they have large displays, graphing calculators also typically display several lines of text and calculations at the same time. Casio produced the first commercially available graphing calculator, the fx-7000G, sharp produced its first graphing calculator, the EL-5200, in 1986. Since then Sharps innovations include models with a touchscreen, Equation Editor, hewlett Packard followed in the form of the HP-28C. This was followed by the HP-28S, HP-48SX, HP-48S, models like the HP 50g or the HP Prime feature a computer algebra system capable of manipulating symbolic expressions and analytic solving. An unusual and powerful CAS calculator is the now obsolete year 2001 Casio Cassiopeia A-10 and A-11 stylus-operated PDAs, the HP series of graphing calculators is best known for its Reverse Polish notation / Reverse Polish Lisp interface, although the HP-49G introduced a standard expression entry interface as well. Texas Instruments has produced graphing calculators since 1990, the oldest of which was the TI-81, some of the newer calculators are similar, with the addition of more memory, faster processors, and USB connection such as the TI-82, TI-83 series, and TI-84 series. Other models, designed to be appropriate for students 10–14 years of age, are the TI-80, other TI graphing calculators have been designed to be appropriate for calculus, namely the TI-85, TI-86, TI-89 series, and TI-92 series. TI offers a CAS on the TI-89, TI-Nspire CAS and TI-92 series of calculators, TI calculators are targeted specifically to the educational market, but are also widely available to the general public. Some graphing calculators have a computer system, which means that they are capable of producing symbolic results. These calculators can manipulate algebraic expressions, performing such as factor, expand. In addition, they can give answers in exact form without numerical approximations, Calculators that have a computer algebra system are called symbolic or CAS calculators. Examples of symbolic calculators include the HP 50g, the HP Prime, the TI-89, the TI-Nspire CAS, student laboratory exercises with data from such devices enhances learning of math, especially statistics and mechanics. Some of the most notable and extensive community-driven graphing calculator archives are ticalc. org and it is simple to download games to a graphing calculator, as nearly all calculator program archives are free and open source. Even though handheld gaming devices fall in a price range. Nowadays graduate students and researchers have turned to advanced Computer Aided Math software for learning as well as experimenting, north America – high school mathematics teachers allow and even encourage their students to use graphing calculators in class. In some cases they are required, some of them are disallowed in certain classes such as chemistry or physics due to their capacity to contain full periodic tables. United Kingdom – a graphing calculator is allowed for A-level maths courses, however they are not required, similarly, at GCSE, all current courses include one paper where no calculator of any kind can be used, but students are permitted to use graphical calculators for other papers
23.
Euclidean space
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In geometry, Euclidean space encompasses the two-dimensional Euclidean plane, the three-dimensional space of Euclidean geometry, and certain other spaces. It is named after the Ancient Greek mathematician Euclid of Alexandria, the term Euclidean distinguishes these spaces from other types of spaces considered in modern geometry. Euclidean spaces also generalize to higher dimensions, classical Greek geometry defined the Euclidean plane and Euclidean three-dimensional space using certain postulates, while the other properties of these spaces were deduced as theorems. Geometric constructions are used to define rational numbers. It means that points of the space are specified with collections of real numbers and this approach brings the tools of algebra and calculus to bear on questions of geometry and has the advantage that it generalizes easily to Euclidean spaces of more than three dimensions. From the modern viewpoint, there is only one Euclidean space of each dimension. With Cartesian coordinates it is modelled by the coordinate space of the same dimension. In one dimension, this is the line, in two dimensions, it is the Cartesian plane, and in higher dimensions it is a coordinate space with three or more real number coordinates. One way to think of the Euclidean plane is as a set of points satisfying certain relationships, expressible in terms of distance, for example, there are two fundamental operations on the plane. One is translation, which means a shifting of the plane so that point is shifted in the same direction. The other is rotation about a point in the plane. In order to all of this mathematically precise, the theory must clearly define the notions of distance, angle, translation. Even when used in theories, Euclidean space is an abstraction detached from actual physical locations, specific reference frames, measurement instruments. The standard way to such space, as carried out in the remainder of this article, is to define the Euclidean plane as a two-dimensional real vector space equipped with an inner product. The reason for working with vector spaces instead of Rn is that it is often preferable to work in a coordinate-free manner. Once the Euclidean plane has been described in language, it is actually a simple matter to extend its concept to arbitrary dimensions. For the most part, the vocabulary, formulae, and calculations are not made any more difficult by the presence of more dimensions. Intuitively, the distinction says merely that there is no choice of where the origin should go in the space
24.
Computer keyboard
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In computing, a computer keyboard is a typewriter-style device which uses an arrangement of buttons or keys to act as a mechanical lever or electronic switch. Following the decline of punch cards and paper tape, interaction via teleprinter-style keyboards became the input device for computers. A keyboard typically has characters engraved or printed on the keys, however, to produce some symbols requires pressing and holding several keys simultaneously or in sequence. While most keyboard keys produce letters, numbers or signs, other keys or simultaneous key presses can produce actions or execute computer commands. In normal usage, the keyboard is used as a text entry interface to type text and numbers into a word processor, in a modern computer, the interpretation of key presses is generally left to the software. A computer keyboard distinguishes each physical key from every other and reports all key presses to the controlling software, Keyboards are also used for computer gaming, either with regular keyboards or by using keyboards with special gaming features, which can expedite frequently used keystroke combinations. A keyboard is used to give commands to the operating system of a computer, such as Windows Control-Alt-Delete combination. A command-line interface is a type of user interface operated entirely through a keyboard and it was through such devices that modern computer keyboards inherited their layouts. Earlier models were developed separately by individuals such as Royal Earl House, earlier, Herman Hollerith developed the first keypunch devices, which soon evolved to include keys for text and number entry akin to normal typewriters by the 1930s. From the 1940s until the late 1960s, typewriters were the means of data entry. The keyboard remained the primary, most integrated computer peripheral well into the era of personal computing until the introduction of the mouse as a device in 1984. By this time, text-only user interfaces with sparse graphics gave way to comparatively graphics-rich icons on screen, One factor determining the size of a keyboard is the presence of duplicate keys, such as a separate numeric keyboard, for convenience. A keyboard with few keys is called a keypad, another factor determining the size of a keyboard is the size and spacing of the keys. Reduction is limited by the consideration that the keys must be large enough to be easily pressed by fingers. Alternatively a tool is used for pressing small keys, standard alphanumeric keyboards have keys that are on three-quarter inch centers, and have a key travel of at least 0.150 inches. Desktop computer keyboards, such as the 101-key US traditional keyboards or the 104-key Windows keyboards, include characters, punctuation symbols, numbers. The internationally common 102/104 key keyboards have a left shift key. Also the enter key is usually shaped differently, computer keyboards are similar to electric-typewriter keyboards but contain additional keys, such as the command or Windows keys
25.
Push-button
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A push-button or simply button is a simple switch mechanism for controlling some aspect of a machine or a process. Buttons are typically out of hard material, usually plastic or metal. The surface is flat or shaped to accommodate the human finger or hand. Buttons are most often biased switches, although many un-biased buttons still require a spring to return to their un-pushed state, different people use different terms for the pushing of the button, such as press, depress, mash, hit, and punch. The push-button has been utilized in calculators, push-button telephones, kitchen appliances, in industrial and commercial applications, push buttons can be connected together by a mechanical linkage so that the act of pushing one button causes the other button to be released. In this way, a button can force a start button to be released. This method of linkage is used in simple manual operations in which the machine or process has no electrical circuits for control, to avoid the operator from pushing the wrong button in error, pushbuttons are often color-coded to associate them with their function. Commonly used colors are red for stopping the machine or process, red pushbuttons can also have large heads for easy operation and to facilitate the stopping of a machine. These pushbuttons are called emergency stop buttons and for increased safety are mandated by the code in many jurisdictions. This large mushroom shape can also be found in buttons for use with operators who need to wear gloves for their work and could not actuate a regular flush-mounted push button. As an aid for operators and users in industrial or commercial applications, typically this light is included into the center of the pushbutton and a lens replaces the pushbutton hard center disk. The source of the energy to illuminate the light is not directly tied to the contacts on the back of the pushbutton, in popular culture, the phrase the button refers to a button that a military or government leader could press to launch nuclear weapons. Spring Return Button by Sándor Kabai, The Wolfram Demonstrations Project
26.
Numerical digit
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A digit is a numeric symbol used in combinations to represent numbers in positional numeral systems. The name digit comes from the fact that the 10 digits of the hands correspond to the 10 symbols of the common base 10 numeral system, i. e. the decimal digits. In a given system, if the base is an integer. For example, the system has ten digits, whereas binary has two digits. In a basic system, a numeral is a sequence of digits. Each position in the sequence has a value, and each digit has a value. The value of the numeral is computed by multiplying each digit in the sequence by its place value, each digit in a number system represents an integer. For example, in decimal the digit 1 represents the one, and in the hexadecimal system. A positional number system must have a digit representing the integers from zero up to, but not including, thus in the positional decimal system, the numbers 0 to 9 can be expressed using their respective numerals 0 to 9 in the rightmost units position. The Hindu–Arabic numeral system uses a decimal separator, commonly a period in English, or a comma in other European languages, to denote the place or units place. Each successive place to the left of this has a value equal to the place value of the previous digit times the base. Similarly, each place to the right of the separator has a place value equal to the place value of the previous digit divided by the base. For example, in the numeral 10, the total value of the number is 1 ten,0 ones,3 tenths, and 4 hundredths. Note that the zero, which contributes no value to the number, the place value of any given digit in a numeral can be given by a simple calculation, which in itself is a compliment to the logic behind numeral systems. And to the right, the digit is multiplied by the base raised by a negative n, for example, in the number 10. This system was established by the 7th century in India, but was not yet in its modern form because the use of the digit zero had not yet widely accepted. Instead of a zero, a dot was left in the numeral as a placeholder, the first widely acknowledged use of zero was in 876. The original numerals were very similar to the ones, even down to the glyphs used to represent digits
27.
Number
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Numbers that answer the question How many. Are 0,1,2,3 and so on, when used to indicate position in a sequence they are ordinal numbers. To the Pythagoreans and Greek mathematician Euclid, the numbers were 2,3,4,5, Euclid did not consider 1 to be a number. Numbers like 3 +17 =227, expressible as fractions in which the numerator and denominator are whole numbers, are rational numbers and these make it possible to measure such quantities as two and a quarter gallons and six and a half miles. What we today would consider a proof that a number is irrational Euclid called a proof that two lengths arising in geometry have no common measure, or are incommensurable, Euclid included proofs of incommensurability of lengths arising in geometry in his Elements. In the Rhind Mathematical Papyrus, a pair of walking forward marked addition. They were the first known civilization to use negative numbers, negative numbers came into widespread use as a result of their utility in accounting. They were used by late medieval Italian bankers, by 1740 BC, the Egyptians had a symbol for zero in accounting texts. In Maya civilization zero was a numeral with a shape as a symbol. The ancient Egyptians represented all fractions in terms of sums of fractions with numerator 1, for example, 2/5 = 1/3 + 1/15. Such representations are known as Egyptian Fractions or Unit Fractions. The earliest written approximations of π are found in Egypt and Babylon, in Babylon, a clay tablet dated 1900–1600 BC has a geometrical statement that, by implication, treats π as 25/8 =3.1250. In Egypt, the Rhind Papyrus, dated around 1650 BC, astronomical calculations in the Shatapatha Brahmana use a fractional approximation of 339/108 ≈3.139. Other Indian sources by about 150 BC treat π as √10 ≈3.1622 The first references to the constant e were published in 1618 in the table of an appendix of a work on logarithms by John Napier. However, this did not contain the constant itself, but simply a list of logarithms calculated from the constant and it is assumed that the table was written by William Oughtred. The discovery of the constant itself is credited to Jacob Bernoulli, the first known use of the constant, represented by the letter b, was in correspondence from Gottfried Leibniz to Christiaan Huygens in 1690 and 1691. Leonhard Euler introduced the letter e as the base for natural logarithms, Euler started to use the letter e for the constant in 1727 or 1728, in an unpublished paper on explosive forces in cannons, and the first appearance of e in a publication was Eulers Mechanica. While in the subsequent years some researchers used the letter c, e was more common, the first numeral system known is Babylonian numeric system, that has a 60 base, it was introduced in 3100 B. C. and is the first Positional numeral system known
28.
Keyboard shortcut
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In computing, a keyboard shortcut is a series of one or several keys that invoke a software or operating system operation when triggered by the user. The meaning of term keyboard shortcut can vary depending on software manufacturer, keyboard shortcuts are generally used to expedite common operations by reducing input sequences to a few keystrokes, hence the term shortcut. To differentiate from general keyboard input, most keyboard shortcuts require the user to press, unmodified key presses are sometimes accepted when the keyboard is not used for general input - such as with graphics packages e. g. Adobe Photoshop or IBM Lotus Freelance Graphics. Other keyboard shortcuts use function keys that are dedicated for use in shortcuts, for simultaneous keyboard shortcuts, one usually first holds down the modifier key, then quickly presses and releases the regular key, and finally releases the modifier key. This distinction is important, as trying to all the keys simultaneously will frequently either miss some of the modifier keys. Sequential shortcuts usually involve pressing and releasing a dedicated key, such as the Esc key. Mnemonics are distinguishable from keyboard shortcuts, in most GUIs, a programs keyboard shortcuts are discoverable by browsing the programs menus – the shortcut is indicated next to the menu choice. There are keyboards that have the shortcuts for an application already marked on them. These keyboards are used for editing video, audio, or graphics. There are also stickers with shortcuts printed on them that can be applied to a regular keyboard, reference cards intended to be propped up in the users workspace also exist for many applications. This highlights a difference in philosophy regarding shortcuts, some systems, typically end-user-oriented systems such as Mac OS or Windows, consider standardized shortcuts essential to the environments ease of use. These systems usually limit a users ability to change shortcuts, possibly even requiring a separate or third-party utility to perform the task, other systems, typically Unix and related, consider shortcuts to be a users prerogative, and that they should be changeable to suit individual preference. For Microsoft Windows, multiple software programs exist like Hotkeycontrol which allow deeper customization of keyboard shortcuts performing advanced tasks, the motivations for customizing key bindings vary. Users new to a program or software environment may customize the new environments keybindings to be similar to another environment with which they are more familiar. More advanced users may customize key bindings to better suit their workflow, adding shortcuts for their commonly used actions, hardcore gamers often customize their key bindings in order to increase performance via faster reaction times. The original Macintosh User Interface Guidelines defined a set of keyboard shortcuts that would remain consistent across application programs and this provides a better user experience than the situation then prevalent of applications using the same keys for different functions. This could result in user errors if one program used ⌘ Command+D to mean Delete while another used it to Duplicate an item, Help Later environments such as Microsoft Windows retain some of these bindings, while adding their own from alternate standards like Common User Access. The simplest keyboard shortcuts consist of one key
29.
Light-emitting diode
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A light-emitting diode is a two-lead semiconductor light source. It is a p–n junction diode, which emits light when activated, when a suitable voltage is applied to the leads, electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is called electroluminescence, and the color of the light is determined by the band gap of the semiconductor. LEDs are typically small and integrated optical components may be used to shape the radiation pattern, appearing as practical electronic components in 1962, the earliest LEDs emitted low-intensity infrared light. Infrared LEDs are still used as transmitting elements in remote-control circuits. The first visible-light LEDs were also of low intensity and limited to red, modern LEDs are available across the visible, ultraviolet, and infrared wavelengths, with very high brightness. Early LEDs were often used as indicator lamps for electronic devices and they were soon packaged into numeric readouts in the form of seven-segment displays and were commonly seen in digital clocks. Recent developments in LEDs permit them to be used in environmental, LEDs have allowed new displays and sensors to be developed, while their high switching rates are also used in advanced communications technology. LEDs have many advantages over incandescent light sources including lower energy consumption, longer lifetime, improved physical robustness, smaller size, and faster switching. Light-emitting diodes are now used in applications as diverse as aviation lighting, automotive headlamps, advertising, general lighting, traffic signals, camera flashes, as of 2017, LED lights home room lighting are as cheap or cheaper than compact fluorescent lamp sources of comparable output. They are also more energy efficient and, arguably, have fewer environmental concerns linked to their disposal. Electroluminescence as a phenomenon was discovered in 1907 by the British experimenter H. J. Round of Marconi Labs, using a crystal of silicon carbide, russian inventor Oleg Losev reported creation of the first LED in 1927. His research was distributed in Soviet, German and British scientific journals, rubin Braunstein of the Radio Corporation of America reported on infrared emission from gallium arsenide and other semiconductor alloys in 1955. Braunstein observed infrared emission generated by simple diode structures using gallium antimonide, GaAs, indium phosphide, in 1957, Braunstein further demonstrated that the rudimentary devices could be used for non-radio communication across a short distance. As noted by Kroemer Braunstein …had set up a simple optical communications link, the emitted light was detected by a PbS diode some distance away. This signal was fed into an amplifier and played back by a loudspeaker. Intercepting the beam stopped the music and we had a great deal of fun playing with this setup. This setup presaged the use of LEDs for optical communication applications, by October 1961, they had demonstrated efficient light emission and signal coupling between a GaAs p-n junction light emitter and an electrically-isolated semiconductor photodetector
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Vacuum fluorescent display
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A vacuum fluorescent display is a display device used commonly on consumer-electronics equipment such as video cassette recorders, car radios, and microwave ovens. Sometimes named as ice tube indicator, a VFD operates on the principle of cathodoluminescence, roughly similar to a cathode ray tube, but operating at much lower voltages. Each tube in a VFD has a phosphor coated anode that is bombarded by electrons emitted from the cathode filament, in fact, each tube in VFD is a triode vacuum tube because it also has a mesh control grid. Unlike liquid crystal displays, a VFD emits a bright light with high contrast. Cadmium was commonly used in VFDs in the past, but the current RoHS-compliant VFDs have eliminated this metal from their construction, VFDs can display seven-segment numerals, multi-segment alpha-numeric characters or can be made in a dot-matrix to display different alphanumeric characters and symbols. In practice, there is little limit to the shape of the image that can be displayed, the first VFD was the single indication DM160 by Philips in 1959. The first multi-segment VFD was the 1962 Japanese single-digit, seven-segment device, the displays became common on calculators and other consumer electronics devices. In the late 1980s hundreds of millions of units were made yearly, the device consists of a hot cathode, anodes and grids encased in a glass envelope under a high vacuum condition. The cathode is made up of fine wires, coated by alkaline earth metal oxides. These electrons are controlled and diffused by the grids, which are made up of thin metal, if electrons impinge on the phosphor-coated plates, they fluoresce, emitting light. Unlike the orange-glowing cathodes of traditional vacuum tubes, VFD cathodes are efficient emitters at much lower temperatures, the principle of operation is identical to that of a vacuum tube triode. Electrons can only reach a given plate element if both the grid and the plate are at a potential with respect to the cathode. This allows the displays to be organized as multiplexed displays where the grids and plates form a matrix. In the example of the VCR display shown to the right, all of the similar plates in all of the digits are connected in parallel. One by one, the microprocessor driving the display enables a digit by placing a positive voltage on that digits grid, electrons flow through that digits grid and strike those plates that are at a positive potential. The microprocessor cycles through illuminating the digits in this way at a high enough to create the illusion of all digits glowing at once via persistence of vision. Several amateurs have experimented with the possibilities of using VFDs as triodes, the extra indicators are arranged as if they were segments of an additional digit or two or extra segments of existing digits and are scanned using the same multiplexed strategy as the real digits. Some of these extra indicators may use a phosphor that emits a different colour of light, for example, orange
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Decimal mark
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A decimal mark is a symbol used to separate the integer part from the fractional part of a number written in decimal form. Different countries officially designate different symbols for the decimal mark, the choice of symbol for the decimal mark also affects the choice of symbol for the thousands separator used in digit grouping, so the latter is also treated in this article. In mathematics the decimal mark is a type of radix point, in the Middle Ages, before printing, a bar over the units digit was used to separate the integral part of a number from its fractional part, e. g.9995. His Compendious Book on Calculation by Completion and Balancing presented the first systematic solution of linear, a similar notation remains in common use as an underbar to superscript digits, especially for monetary values without a decimal mark, e. g.9995. Later, a separatrix between the units and tenths position became the norm among Arab mathematicians, e. g. 99ˌ95, when this character was typeset, it was convenient to use the existing comma or full stop instead. The separatrix was also used in England as an L-shaped or vertical bar before the popularization of the period, gerbert of Aurillac marked triples of columns with an arc when using his Hindu–Arabic numeral-based abacus in the 10th century. Fibonacci followed this convention when writing numbers such as in his influential work Liber Abaci in the 13th century, in France, the full stop was already in use in printing to make Roman numerals more readable, so the comma was chosen. Many other countries, such as Italy, also chose to use the comma to mark the decimal units position and it has been made standard by the ISO for international blueprints. However, English-speaking countries took the comma to separate sequences of three digits, in some countries, a raised dot or dash may be used for grouping or decimal mark, this is particularly common in handwriting. In the United States, the stop or period was used as the standard decimal mark. g. However, as the mid dot was already in use in the mathematics world to indicate multiplication. In the event, the point was decided on by the Ministry of Technology in 1968, the three most spoken international auxiliary languages, Ido, Esperanto, and Interlingua, all use the comma as the decimal mark. Interlingua has used the comma as its decimal mark since the publication of the Interlingua Grammar in 1951, Esperanto also uses the comma as its official decimal mark, while thousands are separated by non-breaking spaces,12345678,9. Idos Kompleta Gramatiko Detaloza di la Linguo Internaciona Ido officially states that commas are used for the mark while full stops are used to separate thousands, millions. So the number 12,345,678.90123 for instance, the 1931 grammar of Volapük by Arie de Jong uses the comma as its decimal mark, and uses the middle dot as the thousands separator. In 1958, disputes between European and American delegates over the representation of the decimal mark nearly stalled the development of the ALGOL computer programming language. ALGOL ended up allowing different decimal marks, but most computer languages, the 22nd General Conference on Weights and Measures declared in 2003 that the symbol for the decimal marker shall be either the point on the line or the comma on the line. It further reaffirmed that numbers may be divided in groups of three in order to facilitate reading, neither dots nor commas are ever inserted in the spaces between groups
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Vulgar fraction
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A fraction represents a part of a whole or, more generally, any number of equal parts. When spoken in everyday English, a fraction describes how many parts of a certain size there are, for example, one-half, eight-fifths, three-quarters. A common, vulgar, or simple fraction consists of an integer numerator displayed above a line, numerators and denominators are also used in fractions that are not common, including compound fractions, complex fractions, and mixed numerals. The numerator represents a number of parts, and the denominator. For example, in the fraction 3/4, the numerator,3, tells us that the fraction represents 3 equal parts, the picture to the right illustrates 34 or ¾ of a cake. Fractional numbers can also be written without using explicit numerators or denominators, by using decimals, percent signs, an integer such as the number 7 can be thought of as having an implicit denominator of one,7 equals 7/1. Other uses for fractions are to represent ratios and to represent division, thus the fraction ¾ is also used to represent the ratio 3,4 and the division 3 ÷4. The test for a number being a number is that it can be written in that form. In a fraction, the number of parts being described is the numerator. Informally, they may be distinguished by placement alone but in formal contexts they are separated by a fraction bar. The fraction bar may be horizontal, oblique, or diagonal and these marks are respectively known as the horizontal bar, the slash or stroke, the division slash, and the fraction slash. In typography, horizontal fractions are known as en or nut fractions and diagonal fractions as em fractions. The denominators of English fractions are expressed as ordinal numbers. When the denominator is 1, it may be expressed in terms of wholes but is commonly ignored. When the numerator is one, it may be omitted, a fraction may be expressed as a single composition, in which case it is hyphenated, or as a number of fractions with a numerator of one, in which case they are not. Fractions should always be hyphenated when used as adjectives, alternatively, a fraction may be described by reading it out as the numerator over the denominator, with the denominator expressed as a cardinal number. The term over is used even in the case of solidus fractions, Fractions with large denominators that are not powers of ten are often rendered in this fashion while those with denominators divisible by ten are typically read in the normal ordinal fashion. A simple fraction is a number written as a/b or a b
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Fractions
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A fraction represents a part of a whole or, more generally, any number of equal parts. When spoken in everyday English, a fraction describes how many parts of a certain size there are, for example, one-half, eight-fifths, three-quarters. A common, vulgar, or simple fraction consists of an integer numerator displayed above a line, numerators and denominators are also used in fractions that are not common, including compound fractions, complex fractions, and mixed numerals. The numerator represents a number of parts, and the denominator. For example, in the fraction 3/4, the numerator,3, tells us that the fraction represents 3 equal parts, the picture to the right illustrates 34 or ¾ of a cake. Fractional numbers can also be written without using explicit numerators or denominators, by using decimals, percent signs, an integer such as the number 7 can be thought of as having an implicit denominator of one,7 equals 7/1. Other uses for fractions are to represent ratios and to represent division, thus the fraction ¾ is also used to represent the ratio 3,4 and the division 3 ÷4. The test for a number being a number is that it can be written in that form. In a fraction, the number of parts being described is the numerator. Informally, they may be distinguished by placement alone but in formal contexts they are separated by a fraction bar. The fraction bar may be horizontal, oblique, or diagonal and these marks are respectively known as the horizontal bar, the slash or stroke, the division slash, and the fraction slash. In typography, horizontal fractions are known as en or nut fractions and diagonal fractions as em fractions. The denominators of English fractions are expressed as ordinal numbers. When the denominator is 1, it may be expressed in terms of wholes but is commonly ignored. When the numerator is one, it may be omitted, a fraction may be expressed as a single composition, in which case it is hyphenated, or as a number of fractions with a numerator of one, in which case they are not. Fractions should always be hyphenated when used as adjectives, alternatively, a fraction may be described by reading it out as the numerator over the denominator, with the denominator expressed as a cardinal number. The term over is used even in the case of solidus fractions, Fractions with large denominators that are not powers of ten are often rendered in this fashion while those with denominators divisible by ten are typically read in the normal ordinal fashion. A simple fraction is a number written as a/b or a b
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Fraction (mathematics)
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A fraction represents a part of a whole or, more generally, any number of equal parts. When spoken in everyday English, a fraction describes how many parts of a certain size there are, for example, one-half, eight-fifths, three-quarters. A common, vulgar, or simple fraction consists of an integer numerator displayed above a line, numerators and denominators are also used in fractions that are not common, including compound fractions, complex fractions, and mixed numerals. The numerator represents a number of parts, and the denominator. For example, in the fraction 3/4, the numerator,3, tells us that the fraction represents 3 equal parts, the picture to the right illustrates 34 or ¾ of a cake. Fractional numbers can also be written without using explicit numerators or denominators, by using decimals, percent signs, an integer such as the number 7 can be thought of as having an implicit denominator of one,7 equals 7/1. Other uses for fractions are to represent ratios and to represent division, thus the fraction ¾ is also used to represent the ratio 3,4 and the division 3 ÷4. The test for a number being a number is that it can be written in that form. In a fraction, the number of parts being described is the numerator. Informally, they may be distinguished by placement alone but in formal contexts they are separated by a fraction bar. The fraction bar may be horizontal, oblique, or diagonal and these marks are respectively known as the horizontal bar, the slash or stroke, the division slash, and the fraction slash. In typography, horizontal fractions are known as en or nut fractions and diagonal fractions as em fractions. The denominators of English fractions are expressed as ordinal numbers. When the denominator is 1, it may be expressed in terms of wholes but is commonly ignored. When the numerator is one, it may be omitted, a fraction may be expressed as a single composition, in which case it is hyphenated, or as a number of fractions with a numerator of one, in which case they are not. Fractions should always be hyphenated when used as adjectives, alternatively, a fraction may be described by reading it out as the numerator over the denominator, with the denominator expressed as a cardinal number. The term over is used even in the case of solidus fractions, Fractions with large denominators that are not powers of ten are often rendered in this fashion while those with denominators divisible by ten are typically read in the normal ordinal fashion. A simple fraction is a number written as a/b or a b
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Decimal
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This article aims to be an accessible introduction. For the mathematical definition, see Decimal representation, the decimal numeral system has ten as its base, which, in decimal, is written 10, as is the base in every positional numeral system. It is the base most widely used by modern civilizations. Decimal fractions have terminating decimal representations and other fractions have repeating decimal representations, Decimal notation is the writing of numbers in a base-ten numeral system. Examples are Brahmi numerals, Greek numerals, Hebrew numerals, Roman numerals, Roman numerals have symbols for the decimal powers and secondary symbols for half these values. Brahmi numerals have symbols for the nine numbers 1–9, the nine decades 10–90, plus a symbol for 100, Chinese numerals have symbols for 1–9, and additional symbols for powers of ten, which in modern usage reach 1072. Positional decimal systems include a zero and use symbols for the ten values to represent any number, positional notation uses positions for each power of ten, units, tens, hundreds, thousands, etc. The position of each digit within a number denotes the multiplier multiplied with that position has a value ten times that of the position to its right. There were at least two independent sources of positional decimal systems in ancient civilization, the Chinese counting rod system. Ten is the number which is the count of fingers and thumbs on both hands, the English word digit as well as its translation in many languages is also the anatomical term for fingers and toes. In English, decimal means tenth, decimate means reduce by a tenth, however, the symbols used in different areas are not identical, for instance, Western Arabic numerals differ from the forms used by other Arab cultures. A decimal fraction is a fraction the denominator of which is a power of ten. g, Decimal fractions 8/10, 1489/100, 24/100000, and 58900/10000 are expressed in decimal notation as 0.8,14.89,0.00024,5.8900 respectively. In English-speaking, some Latin American and many Asian countries, a period or raised period is used as the separator, in many other countries, particularly in Europe. The integer part, or integral part of a number is the part to the left of the decimal separator. The part from the separator to the right is the fractional part. It is usual for a number that consists only of a fractional part to have a leading zero in its notation. Any rational number with a denominator whose only prime factors are 2 and/or 5 may be expressed as a decimal fraction and has a finite decimal expansion. 1/2 =0.5 1/20 =0.05 1/5 =0.2 1/50 =0.02 1/4 =0.25 1/40 =0.025 1/25 =0.04 1/8 =0.125 1/125 =0.008 1/10 =0
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Computer memory
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In computing, memory refers to the computer hardware devices involved to store information for immediate use in a computer, it is synonymous with the term primary storage. Computer memory operates at a speed, for example random-access memory, as a distinction from storage that provides slow-to-access program and data storage. If needed, contents of the memory can be transferred to secondary storage. An archaic synonym for memory is store, there are two main kinds of semiconductor memory, volatile and non-volatile. Examples of non-volatile memory are flash memory and ROM, PROM, EPROM and EEPROM memory, most semiconductor memory is organized into memory cells or bistable flip-flops, each storing one bit. Flash memory organization includes both one bit per cell and multiple bits per cell. The memory cells are grouped into words of fixed word length, each word can be accessed by a binary address of N bit, making it possible to store 2 raised by N words in the memory. This implies that processor registers normally are not considered as memory, since they only store one word, typical secondary storage devices are hard disk drives and solid-state drives. In the early 1940s, memory technology oftenly permit a capacity of a few bytes, the next significant advance in computer memory came with acoustic delay line memory, developed by J. Presper Eckert in the early 1940s. Delay line memory would be limited to a capacity of up to a few hundred thousand bits to remain efficient, two alternatives to the delay line, the Williams tube and Selectron tube, originated in 1946, both using electron beams in glass tubes as means of storage. Using cathode ray tubes, Fred Williams would invent the Williams tube, the Williams tube would prove more capacious than the Selectron tube and less expensive. The Williams tube would prove to be frustratingly sensitive to environmental disturbances. Efforts began in the late 1940s to find non-volatile memory, jay Forrester, Jan A. Rajchman and An Wang developed magnetic core memory, which allowed for recall of memory after power loss. Magnetic core memory would become the dominant form of memory until the development of transistor-based memory in the late 1960s, developments in technology and economies of scale have made possible so-called Very Large Memory computers. The term memory when used with reference to computers generally refers to Random Access Memory or RAM, volatile memory is computer memory that requires power to maintain the stored information. Most modern semiconductor volatile memory is either static RAM or dynamic RAM, SRAM retains its contents as long as the power is connected and is easy for interfacing, but uses six transistors per bit. SRAM is not worthwhile for desktop system memory, where DRAM dominates, SRAM is commonplace in small embedded systems, which might only need tens of kilobytes or less. Forthcoming volatile memory technologies that aim at replacing or competing with SRAM and DRAM include Z-RAM and A-RAM, non-volatile memory is computer memory that can retain the stored information even when not powered
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Formula
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In science, a formula is a concise way of expressing information symbolically as in a mathematical or chemical formula. The informal use of the formula in science refers to the general construct of a relationship between given quantities. The plural of formula can be spelled either as formulas or formulae, in mathematics, a formula is an entity constructed using the symbols and formation rules of a given logical language. Note that the volume V and the radius r are expressed as single instead of words or phrases. This convention, while important in a relatively simple formula, means that mathematicians can more quickly manipulate larger. Mathematical formulas are often algebraic, closed form, and/or analytical, for example, H2O is the chemical formula for water, specifying that each molecule consists of two hydrogen atoms and one oxygen atom. Similarly, O−3 denotes an ozone molecule consisting of three atoms and having a net negative charge. In a general context, formulas are applied to provide a solution for real world problems. Some may be general, F = ma, which is one expression of Newtons second law, is applicable to a range of physical situations. Other formulas may be created to solve a particular problem, for example. In all cases, however, formulas form the basis for calculations, expressions are distinct from formulas in that they cannot contain an equals sign. Whereas formulas are comparable to sentences, expressions are more like phrases, a chemical formula identifies each constituent element by its chemical symbol and indicates the proportionate number of atoms of each element. In empirical formulas, these begin with a key element and then assign numbers of atoms of the other elements in the compound. For molecular compounds, these numbers can all be expressed as whole numbers. For example, the formula of ethanol may be written C2H6O because the molecules of ethanol all contain two carbon atoms, six hydrogen atoms, and one oxygen atom. Some types of compounds, however, cannot be written with entirely whole-number empirical formulas. An example is boron carbide, whose formula of CBn is a variable non-whole number ratio with n ranging from over 4 to more than 6.5. When the chemical compound of the consists of simple molecules
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Array data structure
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In computer science, an array data structure, or simply an array, is a data structure consisting of a collection of elements, each identified by at least one array index or key. An array is stored so that the position of each element can be computed from its index tuple by a mathematical formula, the simplest type of data structure is a linear array, also called one-dimensional array. For example, an array of 10 32-bit integer variables, with indices 0 through 9,2036, so that the element with index i has the address 2000 +4 × i. The memory address of the first element of an array is called first address or foundation address, because the mathematical concept of a matrix can be represented as a two-dimensional grid, two-dimensional arrays are also sometimes called matrices. In some cases the term vector is used in computing to refer to an array, arrays are often used to implement tables, especially lookup tables, the word table is sometimes used as a synonym of array. Arrays are among the oldest and most important data structures, and are used by almost every program and they are also used to implement many other data structures, such as lists and strings. They effectively exploit the addressing logic of computers, in most modern computers and many external storage devices, the memory is a one-dimensional array of words, whose indices are their addresses. Processors, especially vector processors, are optimized for array operations. Arrays are useful mostly because the element indices can be computed at run time, among other things, this feature allows a single iterative statement to process arbitrarily many elements of an array. For that reason, the elements of a data structure are required to have the same size. The set of valid index tuples and the addresses of the elements are usually, Array types are often implemented by array structures, however, in some languages they may be implemented by hash tables, linked lists, search trees, or other data structures. The first digital computers used machine-language programming to set up and access array structures for data tables, vector and matrix computations, john von Neumann wrote the first array-sorting program in 1945, during the building of the first stored-program computer. p. 159 Array indexing was originally done by self-modifying code, and later using index registers, some mainframes designed in the 1960s, such as the Burroughs B5000 and its successors, used memory segmentation to perform index-bounds checking in hardware. Assembly languages generally have no support for arrays, other than what the machine itself provides. The earliest high-level programming languages, including FORTRAN, Lisp, COBOL, and ALGOL60, had support for multi-dimensional arrays, in C++, class templates exist for multi-dimensional arrays whose dimension is fixed at runtime as well as for runtime-flexible arrays. Arrays are used to implement mathematical vectors and matrices, as well as other kinds of rectangular tables, many databases, small and large, consist of one-dimensional arrays whose elements are records. Arrays are used to implement other data structures, such as lists, heaps, hash tables, deques, queues, stacks, strings, one or more large arrays are sometimes used to emulate in-program dynamic memory allocation, particularly memory pool allocation. Historically, this has sometimes been the way to allocate dynamic memory portably