Frequency is the number of occurrences of a repeating event per unit of time. It is referred to as temporal frequency, which emphasizes the contrast to spatial frequency and angular frequency; the period is the duration of time of one cycle in a repeating event, so the period is the reciprocal of the frequency. For example: if a newborn baby's heart beats at a frequency of 120 times a minute, its period—the time interval between beats—is half a second. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals, radio waves, light. For cyclical processes, such as rotation, oscillations, or waves, frequency is defined as a number of cycles per unit time. In physics and engineering disciplines, such as optics and radio, frequency is denoted by a Latin letter f or by the Greek letter ν or ν; the relation between the frequency and the period T of a repeating event or oscillation is given by f = 1 T.
The SI derived unit of frequency is the hertz, named after the German physicist Heinrich Hertz. One hertz means. If a TV has a refresh rate of 1 hertz the TV's screen will change its picture once a second. A previous name for this unit was cycles per second; the SI unit for period is the second. A traditional unit of measure used with rotating mechanical devices is revolutions per minute, abbreviated r/min or rpm. 60 rpm equals one hertz. As a matter of convenience and slower waves, such as ocean surface waves, tend to be described by wave period rather than frequency. Short and fast waves, like audio and radio, are described by their frequency instead of period; these used conversions are listed below: Angular frequency denoted by the Greek letter ω, is defined as the rate of change of angular displacement, θ, or the rate of change of the phase of a sinusoidal waveform, or as the rate of change of the argument to the sine function: y = sin = sin = sin d θ d t = ω = 2 π f Angular frequency is measured in radians per second but, for discrete-time signals, can be expressed as radians per sampling interval, a dimensionless quantity.
Angular frequency is larger than regular frequency by a factor of 2π. Spatial frequency is analogous to temporal frequency, but the time axis is replaced by one or more spatial displacement axes. E.g.: y = sin = sin d θ d x = k Wavenumber, k, is the spatial frequency analogue of angular temporal frequency and is measured in radians per meter. In the case of more than one spatial dimension, wavenumber is a vector quantity. For periodic waves in nondispersive media, frequency has an inverse relationship to the wavelength, λ. In dispersive media, the frequency f of a sinusoidal wave is equal to the phase velocity v of the wave divided by the wavelength λ of the wave: f = v λ. In the special case of electromagnetic waves moving through a vacuum v = c, where c is the speed of light in a vacuum, this expression becomes: f = c λ; when waves from a monochrome source travel from one medium to another, their frequency remains the same—only their wavelength and speed change. Measurement of frequency can done in the following ways, Calculating the frequency of a repeating event is accomplished by counting the number of times that event occurs within a specific time period dividing the count by the length of the time period.
For example, if 71 events occur within 15 seconds the frequency is: f = 71 15 s ≈ 4.73 Hz If the number of counts is not large, it is more accurate to measure the time interval for a predetermined number of occurrences, rather than the number of occurrences within a specified time. The latter method introduces a random error into the count of between zero and one count, so on average half a count; this is called gating error and causes an average error in the calculated frequency of Δ f = 1 2 T
BASIC is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use. In 1964, John G. Kemeny and Thomas E. Kurtz designed the original BASIC language at Dartmouth College, they wanted to enable students in fields other than mathematics to use computers. At the time, nearly all use of computers required writing custom software, something only scientists and mathematicians tended to learn. In addition to the language itself and Kurtz developed the Dartmouth Time Sharing System, which allowed multiple users to edit and run BASIC programs at the same time; this general model became popular on minicomputer systems like the PDP-11 and Data General Nova in the late 1960s and early 1970s. Hewlett-Packard produced an entire computer line for this method of operation, introducing the HP2000 series in the late 1960s and continuing sales into the 1980s. Many early video games trace their history to one of these versions of BASIC; the emergence of early microcomputers in the mid-1970s led to the development of the original Microsoft BASIC in 1975.
Due to the tiny main memory available on these machines 4 kB, a variety of Tiny BASIC dialects were created. BASIC was available for any system of the era, became the de facto programming language for the home computer systems that emerged in the late 1970s; these machines always had a BASIC installed by default in the machine's firmware or sometimes on a ROM cartridge. BASIC fell from use during the 1980s as newer machines with far greater capabilities came to market and other programming languages became tenable. In 1991, Microsoft released Visual Basic, combining a updated version of BASIC with a visual forms builder; this reignited use of the language and "VB" remains a major programming language in the form of VB. NET. John G. Kemeny was the math department chairman at Dartmouth College, on his reputation as an innovator in math teaching, in 1959 the school won an Alfred P. Sloan Foundation award for $500,000 to build a new department building. Thomas E. Kurtz had joined the department in 1956, from the 1960s they agreed on the need for programming literacy among students outside the traditional STEM fields.
Kemeny noted that “Our vision was that every student on campus should have access to a computer, any faculty member should be able to use a computer in the classroom whenever appropriate. It was as simple as that."Kemeny and Kurtz had made two previous experiments with simplified languages, DARSIMCO and DOPE. These did not progress past a single freshman class. New experiments using Fortran and ALGOL followed, but Kurtz concluded these languages were too tricky for what they desired; as Kurtz noted, Fortran had numerous oddly-formed commands, notably an "almost impossible-to-memorize convention for specifying a loop:'DO 100, I = 1, 10, 2'. Is it'1, 10, 2' or'1, 2, 10', is the comma after the line number required or not?"Moreover, the lack of any sort of immediate feedback was a key problem. Kurtz suggested. Small programs would return results in a few seconds; this led to increasing interest in a system using time-sharing and a new language for use by non-STEM students. Kemeny wrote the first version of BASIC.
The acronym BASIC comes from the name of an unpublished paper by Thomas Kurtz. The new language was patterned on FORTRAN II. However, the syntax was changed. For instance, the difficult to remember DO loop was replaced by the much easier to remember FOR I = 1 TO 10 STEP 2, the line number used in the DO was instead indicated by the NEXT I; the cryptic IF statement of Fortran, whose syntax matched a particular instruction of the machine on which it was written, became the simpler IF I=5 THEN GOTO 100. These changes made the language much less idiosyncratic while still having an overall structure and feel similar to the original FORTRAN; the project received a $300,000 grant from the National Science Foundation, used to purchase a GE-225 computer for processing, a Datanet-30 realtime processor to handle the Teletype Model 33 teleprinters used for input and output. A team of a dozen undergraduates worked on the project for about a year, writing both the DTSS system and the BASIC compiler; the main CPU was replaced by a GE-235, still by a GE-635 The first version BASIC language was released on 1 May 1964.
One of the graduate students on the implementation team was Sr. Mary Kenneth Keller, one of the first people in the United States to earn a Ph. D. in computer science and the first woman to do so. BASIC concentrated on supporting straightforward mathematical work, with matrix arithmetic support from its initial implementation as a batch language, character string functionality being added by 1965. Wanting use of the language to become widespread, its designers made the compiler available free of charge, they made it available to high schools in the Hanover, New Hampshire area and put considerable effort into
A nickname is a substitute for the proper name of a familiar person, place, or thing - used for affection. The term hypocoristic is used to refer to a nickname of affection between those in love or with a close emotional bond, compared with a term of endearment, it is a form of amusement. As a concept, it is distinct from both pseudonym and stage name, from a title, although there may be overlap in these concepts. "Moniker" means a nickname or personal name.. The compound word ekename meaning "additional name", was attested as early as 1303; this word was derived from the Old English phrase eaca "an increase", related to eacian "to increase". By the 15th century, the misdivision of the syllables of the phrase "an ekename" led to its rephrasing as "a nekename". Though the spelling has changed, the pronunciation and meaning of the word have remained stable since. To inform an audience or readership of a person's nickname without calling them by their nickname, English nicknames are represented in quotes between the bearer's first and last names.
However, it is common for the nickname to be identified after a comma following the full real name or in the body of the text, such as in an obituary. The middle name is eliminated in speech. Like English, German uses quotation marks between the last names. Other languages may use other conventions; the latter may cause confusion because it resembles an English convention sometimes used for married and maiden names. In Viking societies, many people had heiti, viðrnefni, or kenningarnöfn which were used in addition to, or instead of the first name. In some circumstances, the giving of a nickname had a special status in Viking society in that it created a relationship between the name maker and the recipient of the nickname, to the extent that the creation of a nickname often entailed a formal ceremony and an exchange of gifts known in Old Norse as nafnfestr. Slaves have used nicknames, so that the master who heard about someone doing something could not identify the slave. In capoeira, a Brazilian martial art, the slaves had nicknames to protect them from being caught, as practising capoeira was illegal for decades.
In Anglo-American culture, a nickname is based on a shortening of a person's proper name. However, in other societies, this may not be the case. For example: "my nickname is farmer Phil" In Indian society, for example people have at least one nickname and these affection names are not related to the person's proper name. Indian nicknames often are a trivial word or a diminutive. In Hispanic culture, a nickname is used for a term of endearment and family love, for example: "Papi", it is a colloquial term for “daddy” in Spanish, but in many Spanish-speaking cultures in the Caribbean, it is used as a general term of affection for any man, whether it's a relative, friend, or love. In Australian society, Australian men will give ironic nicknames. For example, a man with red hair will be given the nickname'Blue' or'Bluey'. A tall man will be called ` an obese person ` Slim' and so on. In England, some nicknames are traditionally associated with a person's surname. A man with the surname'Clark' will be nicknamed'Nobby': the surname'Miller' will have the nickname'Dusty': the surname'Adams' has the nickname'Nabby'.
There are several other nicknames linked traditionally with a person's surname, including Chalky White, Bunny Warren, Tug Wilson, Spud Baker. Other English nicknames allude to a person's origins. A Scotsman may be nicknamed'Jock', an Irishman'Paddy' or'Mick', a Welshman may be nicknamed'Taffy'; some nicknames referred to a person's physical characteristics, such as'Lofty' for a short person, or'Curly' for a bald man. Traditional English nicknaming - for men rather than women - was common through the first half of the 20th century, was used in the armed services during World War I and World War II, but has become less common since then. In Chinese culture, nicknames are used within a community among relatives and neighbors. A typical southern Chinese nickname begins with a "阿" followed by another character the last character of the person's given name. For example, Taiwanese politician Chen Shui-bian is sometimes referred as "阿扁". In many Chinese communities of Southeast Asia, nicknames may connote one's occupation or status.
For example, the landlord might be known as Towkay to his tenants or workers while a bread seller would be called "Mianbao Shu" 面包叔. Among Cantonese-speaking communities, the character "仔" may be used in a similar context of "Junior" in Western naming practices. Many writers, performing artists, actors have nicknames, which may
A function key is a key on a computer or terminal keyboard which can be programmed so as to cause an operating system command interpreter or application program to perform certain actions, a form of soft key. On some keyboards/computers, function keys may have default actions, accessible on power-on. Function keys on a terminal may either generate short fixed sequences of characters beginning with the escape character, or the characters they generate may be configured by sending special character sequences to the terminal. On a standard computer keyboard, the function keys may generate a fixed, single byte code, outside the normal ASCII range, translated into some other configurable sequence by the keyboard device driver or interpreted directly by the application program. Function keys may have default actions printed on/besides them, or they may have the more common "F-number" designations; the Singer/Friden 2201 Flexowriter Programatic, introduced in 1965, had a cluster of 13 function keys, labeled F1 to F13 to the right of the main keyboard.
Although the Flexowriter could be used as a computer terminal, this electromechanical typewriter was intended as a stand-alone word processing system. The interpretation of the function keys was determined by the programming of a plugboard inside the back of the machine. Soft keys date to avionics multi-function displays of military planes of the late 1960s/early 1970s, such as the Mark II avionics of the F-111D. In computing use, they were found on the HP 9810A calculator and models of the HP 9800 series, which featured 10 programmable keys in 5×2 block at the top left of the keyboard, with paper labels; the HP 9830A was an early desktop computer, one of the earliest computing uses. HP continued its use of function keys in the HP 2640, which used screen-labeled function keys, placing the keys close to the screen, where labels could be displayed for their function. NEC's PC-8001, introduced in 1979, featured five function keys at the top of the keyboard, along with a numeric keypad on the right-hand side of the keyboard.
Their modern use may have been popularized by IBM keyboards: first the IBM 3270 terminals the IBM PC. IBM use of function keys dates to the IBM 3270 line of terminals the IBM 3277 with 78-key typewriter keyboard or operator console keyboard version, which both featured 12 programmed function keys in a 3×4 matrix at the right of the keyboard. Models replaced this with a numeric keypad, moved the function keys to 24 keys at the top of the keyboard; the original IBM PC keyboard had 10 function keys in a 2×5 matrix at the left of the keyboard. Since the introduction of the Apple Extended Keyboard with the Macintosh II, keyboards with function keys have been available, though they did not become standard until the mid-1990s, they have not traditionally been a major part of the Mac user interface and are only used on cross-platform programs. According to the Macintosh Human Interface Guidelines, they are reserved for customization by the user. Current Mac keyboards include specialized function keys for controlling sound volume.
The most recent Mac keyboards include 19 function keys, but keys F1–F4 and F7–F12 by default control features such as volume, media control, Exposé. Former keyboards and Apple Keyboard with numeric keypad has the F1–F19 keys. Apple Macintosh notebooks: Function keys were not standard on Apple notebook hardware until the introduction of the PowerBook 5300 and the PowerBook 190. For the most part, Mac laptops have keys F1 through F12, with pre-defined actions for some, including controlling sound volume and screen brightness. Apricot PC/Xi: six unlabelled keys, each with an LED beside it which illuminates when the key can be used. Atari 8-bit family: four dedicated keys at the right hand side or on the top of the keyboard. Atari 1200XL had four additional keys labeled F1 through F4 with pre-defined actions related to cursor movement. Atari ST: ten parallelogram-shaped keys in a horizontal row across the top of the keyboard, inset into the keyboard frame instead of popping up like normal keys. BBC Micro: red/orange keys F0 to F9 in a horizontal row above the number keys on top of the computer/keyboard.
The break and copy keys could function as F10–F15. The case included a transparent plastic strip above them to hold a function key reference card. Coleco Adam: six dark brown keys in a horizontal row above the number keys, labeled with Roman numerals I–VI. Commodore VIC-20 and C64: F1/F2 to F7/F8 in a vertical row of four keys ascending downwards on the computer/keyboard's right hand side, odd-numbered functions accessed unshifted, even-numbered shifted. Commodore 128: same as VIC-20/C64, but with function keys placed in a horizontal row above the numeric keypad right of the main QWERTY-keyboard. Commodore Amiga: ten keys ar
Microsoft Corporation is an American multinational technology company with headquarters in Redmond, Washington. It develops, licenses and sells computer software, consumer electronics, personal computers, related services, its best known software products are the Microsoft Windows line of operating systems, the Microsoft Office suite, the Internet Explorer and Edge web browsers. Its flagship hardware products are the Xbox video game consoles and the Microsoft Surface lineup of touchscreen personal computers; as of 2016, it is the world's largest software maker by revenue, one of the world's most valuable companies. The word "Microsoft" is a portmanteau of "microcomputer" and "software". Microsoft is ranked No. 30 in the 2018 Fortune 500 rankings of the largest United States corporations by total revenue. Microsoft was founded by Bill Gates and Paul Allen on April 4, 1975, to develop and sell BASIC interpreters for the Altair 8800, it rose to dominate the personal computer operating system market with MS-DOS in the mid-1980s, followed by Microsoft Windows.
The company's 1986 initial public offering, subsequent rise in its share price, created three billionaires and an estimated 12,000 millionaires among Microsoft employees. Since the 1990s, it has diversified from the operating system market and has made a number of corporate acquisitions, their largest being the acquisition of LinkedIn for $26.2 billion in December 2016, followed by their acquisition of Skype Technologies for $8.5 billion in May 2011. As of 2015, Microsoft is market-dominant in the IBM PC-compatible operating system market and the office software suite market, although it has lost the majority of the overall operating system market to Android; the company produces a wide range of other consumer and enterprise software for desktops and servers, including Internet search, the digital services market, mixed reality, cloud computing and software development. Steve Ballmer replaced Gates as CEO in 2000, envisioned a "devices and services" strategy; this began with the acquisition of Danger Inc. in 2008, entering the personal computer production market for the first time in June 2012 with the launch of the Microsoft Surface line of tablet computers.
Since Satya Nadella took over as CEO in 2014, the company has scaled back on hardware and has instead focused on cloud computing, a move that helped the company's shares reach its highest value since December 1999. In 2018, Microsoft surpassed Apple as the most valuable publicly traded company in the world after being dethroned by the tech giant in 2010. Childhood friends Bill Gates and Paul Allen sought to make a business utilizing their shared skills in computer programming. In 1972 they founded their first company, named Traf-O-Data, which sold a rudimentary computer to track and analyze automobile traffic data. While Gates enrolled at Harvard, Allen pursued a degree in computer science at Washington State University, though he dropped out of school to work at Honeywell; the January 1975 issue of Popular Electronics featured Micro Instrumentation and Telemetry Systems's Altair 8800 microcomputer, which inspired Allen to suggest that they could program a BASIC interpreter for the device. After a call from Gates claiming to have a working interpreter, MITS requested a demonstration.
Since they didn't yet have one, Allen worked on a simulator for the Altair while Gates developed the interpreter. Although they developed the interpreter on a simulator and not the actual device, it worked flawlessly when they demonstrated the interpreter to MITS in Albuquerque, New Mexico. MITS agreed to distribute it, marketing it as Altair BASIC. Gates and Allen established Microsoft on April 4, 1975, with Gates as the CEO; the original name of "Micro-Soft" was suggested by Allen. In August 1977 the company formed an agreement with ASCII Magazine in Japan, resulting in its first international office, "ASCII Microsoft". Microsoft moved to a new home in Bellevue, Washington in January 1979. Microsoft entered the operating system business in 1980 with its own version of Unix, called Xenix. However, it was MS-DOS. After negotiations with Digital Research failed, IBM awarded a contract to Microsoft in November 1980 to provide a version of the CP/M OS, set to be used in the upcoming IBM Personal Computer.
For this deal, Microsoft purchased a CP/M clone called 86-DOS from Seattle Computer Products, which it branded as MS-DOS, though IBM rebranded it to PC DOS. Following the release of the IBM PC in August 1981, Microsoft retained ownership of MS-DOS. Since IBM had copyrighted the IBM PC BIOS, other companies had to reverse engineer it in order for non-IBM hardware to run as IBM PC compatibles, but no such restriction applied to the operating systems. Due to various factors, such as MS-DOS's available software selection, Microsoft became the leading PC operating systems vendor; the company expanded into new markets with the release of the Microsoft Mouse in 1983, as well as with a publishing division named Microsoft Press. Paul Allen resigned from Microsoft in 1983 after developing Hodgkin's disease. Allen claimed that Gates wanted to dilute his share in the company when he was diagnosed with Hodgkin's disease because he didn't think he was working hard enough. After leaving Microsoft, Allen lost billions of dollars on ill-conceived or mistimed technology investments.
He invested in low-tech sectors, sports teams, commercial real estate. Despite having begun jointly developing a new operating system, OS/2, with IBM in
Greg Whitten is an American computer engineer and car collector. Whitten graduated from the University of Virginia with a B. A. in mathematics in 1973, from Harvard University with a Ph. D. in applied mathematics in 1978. He worked for Compucolor, a company in Georgia established in 1977 that made the home computer Compucolor II but ran out of business in 1983. While here, he reputedly optimized an unlicensed copy of Microsoft Basic so that Microsoft forgave Compucolor for their infringement in exchange for the rights to the enhancements, he worked for Microsoft from 1979 to 1998. He developed the standards for the company's BASIC compiler line."GW" in the name of the GW-BASIC dialect of BASIC developed by Microsoft may have come from Greg Whitten's initials: "The GW-BASIC name stands for Gee-Whiz BASIC. The GW- name was picked by Bill Gates, he is the one. I did set the directions for the BASIC language features after joining the company in 1979." - Greg Whitten, 13 Apr 2005As a chief software architect, he oversaw the development of the enterprise support systems required in Windows for the Microsoft Office.
In 1998 he became member of the board of Numerix, a financial software company established 1996, where he had made a major investment and in 2001 was elected Boardman after another major investment. After being its CEO 2003–13, he was succeeded by Steve O'Hanlon, he is a vintage car enthusiast and has a famous car collection that contains various Ferraris including his first, a Ferrari F40, a Ferrari Enzo, a Ferrari 250 GTO, a Ferrari 250 LM, a Ferrari 250 GT TdF, a Ferrari F50, two LaFerrari, of which one is the unique in blue electrics. His Ferrari 250 GTO sold for $48.8 million at a public auction in August 2018
In computing, floating-point arithmetic is arithmetic using formulaic representation of real numbers as an approximation so as to support a trade-off between range and precision. For this reason, floating-point computation is found in systems which include small and large real numbers, which require fast processing times. A number is, in general, represented to a fixed number of significant digits and scaled using an exponent in some fixed base. A number that can be represented is of the following form: significand × base exponent, where significand is an integer, base is an integer greater than or equal to two, exponent is an integer. For example: 1.2345 = 12345 ⏟ significand × 10 ⏟ base − 4 ⏞ exponent. The term floating point refers to the fact that a number's radix point can "float"; this position is indicated as the exponent component, thus the floating-point representation can be thought of as a kind of scientific notation. A floating-point system can be used to represent, with a fixed number of digits, numbers of different orders of magnitude: e.g. the distance between galaxies or the diameter of an atomic nucleus can be expressed with the same unit of length.
The result of this dynamic range is that the numbers that can be represented are not uniformly spaced. Over the years, a variety of floating-point representations have been used in computers. In 1985, the IEEE 754 Standard for Floating-Point Arithmetic was established, since the 1990s, the most encountered representations are those defined by the IEEE; the speed of floating-point operations measured in terms of FLOPS, is an important characteristic of a computer system for applications that involve intensive mathematical calculations. A floating-point unit is a part of a computer system specially designed to carry out operations on floating-point numbers. A number representation specifies some way of encoding a number as a string of digits. There are several mechanisms. In common mathematical notation, the digit string can be of any length, the location of the radix point is indicated by placing an explicit "point" character there. If the radix point is not specified the string implicitly represents an integer and the unstated radix point would be off the right-hand end of the string, next to the least significant digit.
In fixed-point systems, a position in the string is specified for the radix point. So a fixed-point scheme might be to use a string of 8 decimal digits with the decimal point in the middle, whereby "00012345" would represent 0001.2345. In scientific notation, the given number is scaled by a power of 10, so that it lies within a certain range—typically between 1 and 10, with the radix point appearing after the first digit; the scaling factor, as a power of ten, is indicated separately at the end of the number. For example, the orbital period of Jupiter's moon Io is 152,853.5047 seconds, a value that would be represented in standard-form scientific notation as 1.528535047×105 seconds. Floating-point representation is similar in concept to scientific notation. Logically, a floating-point number consists of: A signed digit string of a given length in a given base; this digit string is referred to mantissa, or coefficient. The length of the significand determines the precision; the radix point position is assumed always to be somewhere within the significand—often just after or just before the most significant digit, or to the right of the rightmost digit.
This article follows the convention that the radix point is set just after the most significant digit. A signed integer exponent. To derive the value of the floating-point number, the significand is multiplied by the base raised to the power of the exponent, equivalent to shifting the radix point from its implied position by a number of places equal to the value of the exponent—to the right if the exponent is positive or to the left if the exponent is negative. Using base-10 as an example, the number 152,853.5047, which has ten decimal digits of precision, is represented as the significand 1,528,535,047 together with 5 as the exponent. To determine the actual value, a decimal point is placed after the first digit of the significand and the result is multiplied by 105 to give 1.528535047×105, or 152,853.5047. In storing such a number, the base need not be stored, since it will be the same for the entire range of supported numbers, can thus be inferred. Symbolically, this final value is: s b p − 1 × b e, where s is the