Computer
A computer is a device that can be instructed to carry out sequences of arithmetic or logical operations automatically via computer programming. Modern computers have the ability to follow generalized sets of called programs; these programs enable computers to perform an wide range of tasks. A "complete" computer including the hardware, the operating system, peripheral equipment required and used for "full" operation can be referred to as a computer system; this term may as well be used for a group of computers that are connected and work together, in particular a computer network or computer cluster. Computers are used as control systems for a wide variety of industrial and consumer devices; this includes simple special purpose devices like microwave ovens and remote controls, factory devices such as industrial robots and computer-aided design, general purpose devices like personal computers and mobile devices such as smartphones. The Internet is run on computers and it connects hundreds of millions of other computers and their users.
Early computers were only conceived as calculating devices. Since ancient times, simple manual devices like the abacus aided people in doing calculations. Early in the Industrial Revolution, some mechanical devices were built to automate long tedious tasks, such as guiding patterns for looms. More sophisticated electrical machines did specialized analog calculations in the early 20th century; the first digital electronic calculating machines were developed during World War II. The speed and versatility of computers have been increasing ever since then. Conventionally, a modern computer consists of at least one processing element a central processing unit, some form of memory; the processing element carries out arithmetic and logical operations, a sequencing and control unit can change the order of operations in response to stored information. Peripheral devices include input devices, output devices, input/output devices that perform both functions. Peripheral devices allow information to be retrieved from an external source and they enable the result of operations to be saved and retrieved.
According to the Oxford English Dictionary, the first known use of the word "computer" was in 1613 in a book called The Yong Mans Gleanings by English writer Richard Braithwait: "I haue read the truest computer of Times, the best Arithmetician that euer breathed, he reduceth thy dayes into a short number." This usage of the term referred to a human computer, a person who carried out calculations or computations. The word continued with the same meaning until the middle of the 20th century. During the latter part of this period women were hired as computers because they could be paid less than their male counterparts. By 1943, most human computers were women. From the end of the 19th century the word began to take on its more familiar meaning, a machine that carries out computations; the Online Etymology Dictionary gives the first attested use of "computer" in the 1640s, meaning "one who calculates". The Online Etymology Dictionary states that the use of the term to mean "'calculating machine' is from 1897."
The Online Etymology Dictionary indicates that the "modern use" of the term, to mean "programmable digital electronic computer" dates from "1945 under this name. Devices have been used to aid computation for thousands of years using one-to-one correspondence with fingers; the earliest counting device was a form of tally stick. Record keeping aids throughout the Fertile Crescent included calculi which represented counts of items livestock or grains, sealed in hollow unbaked clay containers; the use of counting rods is one example. The abacus was used for arithmetic tasks; the Roman abacus was developed from devices used in Babylonia as early as 2400 BC. Since many other forms of reckoning boards or tables have been invented. In a medieval European counting house, a checkered cloth would be placed on a table, markers moved around on it according to certain rules, as an aid to calculating sums of money; the Antikythera mechanism is believed to be the earliest mechanical analog "computer", according to Derek J. de Solla Price.
It was designed to calculate astronomical positions. It was discovered in 1901 in the Antikythera wreck off the Greek island of Antikythera, between Kythera and Crete, has been dated to c. 100 BC. Devices of a level of complexity comparable to that of the Antikythera mechanism would not reappear until a thousand years later. Many mechanical aids to calculation and measurement were constructed for astronomical and navigation use; the planisphere was a star chart invented by Abū Rayhān al-Bīrūnī in the early 11th century. The astrolabe was invented in the Hellenistic world in either the 1st or 2nd centuries BC and is attributed to Hipparchus. A combination of the planisphere and dioptra, the astrolabe was an analog computer capable of working out several different kinds of problems in spherical astronomy. An astrolabe incorporating a mechanical calendar computer and gear-wheels was invented by Abi Bakr of Isfahan, Persia in 1235. Abū Rayhān al-Bīrūnī invented the first mechanical geared lunisolar calendar astrolabe, an early fixed-wired knowledge processing machine with a gear train and gear-wheels, c. 1000 AD.
The sector, a calculating instrument used for solving problems in proportion, trigonometry and division, for various functions, such as squares and cube roots, was developed in
Electronics
Electronics comprises the physics, engineering and applications that deal with the emission and control of electrons in vacuum and matter. The identification of the electron in 1897, along with the invention of the vacuum tube, which could amplify and rectify small electrical signals, inaugurated the field of electronics and the electron age. Electronics deals with electrical circuits that involve active electrical components such as vacuum tubes, diodes, integrated circuits and sensors, associated passive electrical components, interconnection technologies. Electronic devices contain circuitry consisting or of active semiconductors supplemented with passive elements; the nonlinear behaviour of active components and their ability to control electron flows makes amplification of weak signals possible. Electronics is used in information processing, telecommunication, signal processing; the ability of electronic devices to act as switches makes digital information-processing possible. Interconnection technologies such as circuit boards, electronics packaging technology, other varied forms of communication infrastructure complete circuit functionality and transform the mixed electronic components into a regular working system, called an electronic system.
An electronic system may be a component of a standalone device. Electrical and electromechanical science and technology deals with the generation, switching and conversion of electrical energy to and from other energy forms; this distinction started around 1906 with the invention by Lee De Forest of the triode, which made electrical amplification of weak radio signals and audio signals possible with a non-mechanical device. Until 1950 this field was called "radio technology" because its principal application was the design and theory of radio transmitters and vacuum tubes; as of 2018 most electronic devices use semiconductor components to perform electron control. The study of semiconductor devices and related technology is considered a branch of solid-state physics, whereas the design and construction of electronic circuits to solve practical problems come under electronics engineering; this article focuses on engineering aspects of electronics. Digital electronics Analogue electronics Microelectronics Circuit design Integrated circuits Power electronics Optoelectronics Semiconductor devices Embedded systems An electronic component is any physical entity in an electronic system used to affect the electrons or their associated fields in a manner consistent with the intended function of the electronic system.
Components are intended to be connected together by being soldered to a printed circuit board, to create an electronic circuit with a particular function. Components may be packaged singly, or in more complex groups as integrated circuits; some common electronic components are capacitors, resistors, transistors, etc. Components are categorized as active or passive. Vacuum tubes were among the earliest electronic components, they were solely responsible for the electronics revolution of the first half of the twentieth century. They allowed for vastly more complicated systems and gave us radio, phonographs, long-distance telephony and much more, 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 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.
In April 1955, the IBM 608 was the first IBM product to use transistor circuits without any vacuum tubes and is believed to be the first all-transistorized calculator to be manufactured for the commercial market. 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 exclusively used for computer logic and peripherals. Circuits and components can be divided into two groups: digital. A particular device may consist of circuitry that has 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 continuous 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 because a'circuit' can be defined as anything from a single component, to systems containing thousands of components.
Analog circuits are sometimes called linear circuits although many non-linear effects are used in analog circuits such as mixers, etc. Good examples of analog circuits include vacuum tube and transistor amplifiers, operational amplifiers and oscillators. One finds modern circuits that are analog; these days analog circuitry may use digital or microprocessor techniques to improve performance. This type of circuit is 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
Aberdeen Proving Ground
Aberdeen Proving Ground is a United States Army facility located adjacent to Aberdeen, Maryland. Part of the facility is a census-designated place, which had a population of 3,116 at the 2000 census, 2,093 at the 2010 census. APG is the U. S. Army's oldest active proving ground, established on October 20, 1917, six months after the U. S. entered World War I. Its location allowed design and testing of ordnance materiel to take place near contemporary industrial and shipping centers; the proving ground was created as a successor to the Sandy Hook Proving Ground, too small for some of the larger weapons being tested. At the peak of World War II, APG had billeting space for 2,348 officers and 24,189 enlisted personnel. Although civilian contractors produced the major portion of conventional munitions for World War I, the United States government built federally owned plants on Aberdeen Proving Ground for the manufacture of toxic gas; these poison gas manufacturing facilities came to be known as Edgewood Arsenal.
Edgewood Arsenal included plants to manufacture mustard gas and phosgene, separate facilities to fill artillery shells with these chemicals. Production began in 1918, reached 2,756 tons per month, totaled 10,817 tons of toxic gas manufactured at Edgewood Arsenal before the November 1918 armistice; some of this gas was shipped overseas for use in British artillery shells. The Edgewood area of Aberdeen Proving Ground is 13,000 acres; the Edgewood area was used for the testing of chemical agent munitions. From 1917 to the present, the Edgewood area conducted chemical research programs, manufactured chemical agents, tested and disposed of toxic materials. From 1955 to 1975, the U. S. Army Chemical Corps conducted classified medical studies at Maryland; the purpose was to evaluate the impact of low-dose chemical warfare agents on military personnel and to test protective clothing and pharmaceuticals. About 7,000 soldiers took part in these experiments that involved exposures to more than 250 different chemicals, according to the Department of Defense.
Some of the volunteers exhibited symptoms at the time of exposure to these agents but long-term follow-up was not planned as part of the DoD studies. The agents tested included chemical warfare agents and other related agents: Anticholinesterase nerve agents Mustard agent Nerve agent antidotes atropine and scopolamine Nerve agent reactivators Psychoactive agents Irritants and riot control agents Alcohol and caffeineDuring the week of July 14, 1969, personnel from Naval Applied Science Laboratory in conjunction with personnel from Limited War Laboratory conducted a defoliation test along the shoreline of Poole's Island, Aberdeen Proving Ground using Agent Orange and Agent Orange Plus foam; the Gunpowder Meetinghouse and Presbury Meetinghouse located within the grounds of Edgewood Arsenal are listed on the National Register of Historic Places. Other parts of APG not attached to the main installation include the Churchville Test Area in Harford County, the Carroll Island and Graces Quarters in Baltimore County, Maryland.
The Churchville Test Area is a test track with hills that provide steep natural grades and tight turns to stress engines and suspensions for army vehicles, including M1 Abrams tanks, Bradley Fighting Vehicles, Humvees. The eastern half Carroll Island was used as a testing location for open air static testing of chemical weapons since the 1950s. During tests of chemical agents and other compounds at Carroll Island, from July 1, 1964, to December 31, 1971, nearly 6.5 short tons of chemicals were disseminated on the test area including 4,600 pounds of irritants, 655 pounds of anticholinesterase compounds such as the nerve gasses Sarin and VX, 263 pounds of incapacitants such as LSD. Simulant agents, decontaminating compounds and screening smokes and herbicides were released as well as riot control gasses; the test sites consisted of spray grids, a wind tunnel, test grids, small buildings. Edgewood Chemical Activity is a chemical-weapons depot located at APG. Elimination of the chemicals held here was put on an accelerated schedule after the September 11, 2001, all chemical weapons were destroyed by February 2006.
Fort Hoyle was established on October 7, 1922, was created from a portion of the Edgewood Arsenal. Named for Brigadier General Eli D. Hoyle, who had commanded the 6th Field Artillery Regiment, the post was home to Headquarters, 1st Field Artillery Brigade, the 6th Field Artillery Regiment, the 1st Ammunition Train, the 99th Field Artillery Regiment. Fort Hoyle was disestablished as a separate military post when it was reabsorbed by Edgewood Arsenal on September 10, 1940; the U. S. Army Ordnance Corps Museum located at APG, was moved to Fort Lee, Virginia, as a result of the 2005 Base Realignment and Closure Act. APG occupies a land area of 293 square kilometres, its northernmost point is near the mouth of the Susquehanna River, where the river enters the Chesapeake Bay, while on the south, it is bordered by the Gunpowder River. The installation lies on two peninsulas separated by the Bush River; the northeastern is known as the Aberdeen Area and the southwestern is called the Edgewood Area. According to the U.
S. Census Bureau, the
J. Presper Eckert
John Adam Presper "Pres" Eckert Jr. was an American electrical engineer and computer pioneer. With John Mauchly, he designed the first general-purpose electronic digital computer, presented the first course in computing topics, founded the Eckert–Mauchly Computer Corporation, designed the first commercial computer in the U. S. the UNIVAC, which incorporated Eckert's invention of the mercury delay line memory. Eckert was born in Philadelphia to wealthy real estate developer John Eckert, was raised in a large house in Philadelphia's Germantown section. During elementary school, he was driven by chauffeur to William Penn Charter School, in high school joined the Engineer's Club of Philadelphia and spent afternoons at the electronics laboratory of television inventor Philo Farnsworth in Chestnut Hill, he placed second in the country on the math portion of the College Board examination. Eckert enrolled in the University of Pennsylvania's Wharton School to study business at the encouragement of his parents, but in 1937 transferred to Penn's Moore School of Electrical Engineering.
In 1940, at age 21, Eckert applied for his first patent, "Light Modulating Method and Apparatus". At the Moore School, Eckert participated in research on radar timing, made improvements to the speed and precision of the Moore School's differential analyzer, in 1941 assisted in teaching a summer course in electronics under the Engineering and Management War Training offered through the Moore School by the United States Department of War. Dr. John Mauchly chairman of the physics department of nearby Ursinus College, was a student in the summer electronics course, the following fall secured a teaching position at the Moore School. Mauchly's proposal for building an electronic digital computer using vacuum tubes, many times faster and more accurate than the Differential analyzer for computing ballistics tables for artillery, caught the interest of the Moore School's Army liaison, Lieutenant Herman Goldstine, on April 9, 1943, was formally presented in a meeting at Aberdeen Proving Ground to director Colonel Leslie Simon, Oswald Veblen, others.
A contract was awarded for Moore School's construction of the proposed computing machine, which would be named ENIAC, Eckert was made the project's chief engineer. ENIAC was completed in late 1945 and was unveiled to the public in February 1946. Both Eckert and Mauchly left the Moore School in March 1946 over a dispute involving assignment of claims on intellectual property developed at the University. In that year, the University of Pennsylvania adopted a new patent policy to protect the intellectual purity of the research it sponsored, which would have required Eckert and Mauchly to assign all their patents to the University had they stayed beyond March. Eckert and Mauchly's agreement with the University of Pennsylvania was that Eckert and Mauchly retained the patent rights to the ENIAC but the University could license it to the government and non-profit organizations; the University wanted to change the agreement so that they would have commercial rights to the patent. In the following months and Mauchly started up the Electronic Control Company which built the Binary Automatic Computer.
One of the major advances of this machine, used from August 1950, was that data was stored on magnetic tape. The Electronic Control Company soon became the Eckert–Mauchly Computer Corporation, it received an order from the National Bureau of Standards to build the Universal Automatic Computer, he was awarded the Howard N. Potts Medal in 1949. In 1950, Eckert–Mauchly Computer Corporation ran into financial troubles and was acquired by Remington Rand Corporation; the UNIVAC I was finished on December 21, 1950. In 1968, "For pioneering and continuing contributions in creating and improving the high-speed electronic digital computer", he was awarded the National Medal of Science. Eckert became an executive within the company, he continued with Remington Rand as it merged with the Burroughs Corporation to become Unisys in 1986. In 1989, Eckert continued to act as a consultant for the company, he died of leukemia in Pennsylvania. In 2002, he was inducted, into the National Inventors Hall of Fame. Eckert believed that the adopted term "von Neumann architecture" should properly be known as the "Eckert architecture", since the stored-program concept central to the von Neumann architecture had been developed at the Moore School by the time von Neumann arrived on the scene in 1944–1945.
Eckert's contention that von Neumann improperly took credit for devising the stored program computer architecture was supported by Jean Bartik, one of the original ENIAC programmers. Many others in the field, believe that the concept of a stored program predates both of these men, going as far back as Charles Babbage and others. List of pioneers in computer science Lukoff, Herman. From Dits to Bits: A personal history of the electronic computer. Portland, Oregon, USA: Robotics Press. ISBN 0-89661-002-0. LCCN 79-90567. Oral history interview with J. Presper Eckert, Charles Babbage Institute, University of Minnesota. Eckert, a co-inventor of the ENIAC, discusses its development at the University of Pennsylvania's Moore School of Electrical Engineering. Interview by Nancy Stern, October 28, 1977. Oral history interview with Carl Chambers, Charles Babbage Institute, University of Minnesota. Describes the intera
John von Neumann
John von Neumann was a Hungarian-American mathematician, computer scientist, polymath. Von Neumann was regarded as the foremost mathematician of his time and said to be "the last representative of the great mathematicians", he made major contributions to a number of fields, including mathematics, economics and statistics. He was a pioneer of the application of operator theory to quantum mechanics in the development of functional analysis, a key figure in the development of game theory and the concepts of cellular automata, the universal constructor and the digital computer, he published over 150 papers in his life: about 60 in pure mathematics, 60 in applied mathematics, 20 in physics, the remainder on special mathematical subjects or non-mathematical ones. His last work, an unfinished manuscript written while in hospital, was published in book form as The Computer and the Brain, his analysis of the structure of self-replication preceded the discovery of the structure of DNA. In a short list of facts about his life he submitted to the National Academy of Sciences, he stated, "The part of my work I consider most essential is that on quantum mechanics, which developed in Göttingen in 1926, subsequently in Berlin in 1927–1929.
My work on various forms of operator theory, Berlin 1930 and Princeton 1935–1939. During World War II, von Neumann worked on the Manhattan Project with theoretical physicist Edward Teller, mathematician Stanisław Ulam and others, problem solving key steps in the nuclear physics involved in thermonuclear reactions and the hydrogen bomb, he developed the mathematical models behind the explosive lenses used in the implosion-type nuclear weapon, coined the term "kiloton", as a measure of the explosive force generated. After the war, he served on the General Advisory Committee of the United States Atomic Energy Commission, consulted for a number of organizations, including the United States Air Force, the Army's Ballistic Research Laboratory, the Armed Forces Special Weapons Project, the Lawrence Livermore National Laboratory; as a Hungarian émigré, concerned that the Soviets would achieve nuclear superiority, he designed and promoted the policy of mutually assured destruction to limit the arms race.
Von Neumann was born Neumann János Lajos to a wealthy and non-observant Jewish family. After his arrival in the U. S. he had been baptized a Roman Catholic prior to the marriage to his Catholic first wife. Von Neumann was born in Budapest, Kingdom of Hungary, part of the Austro-Hungarian Empire, he was the eldest of three brothers. His father, Neumann Miksa was a banker, he had moved to Budapest from Pécs at the end of the 1880s. Miksa's father and grandfather were both born in Zemplén County, northern Hungary. John's mother was Kann Margit. Three generations of the Kann family lived in spacious apartments above the Kann-Heller offices in Budapest. On February 20, 1913, Emperor Franz Joseph elevated his father to the Hungarian nobility for his service to the Austro-Hungarian Empire; the Neumann family thus acquired the hereditary appellation Margittai. The family had no connection with the town. Neumann János became margittai Neumann János, which he changed to the German Johann von Neumann. Von Neumann was a child prodigy.
When he was 6 years old, he could divide two 8-digit numbers in his head and could converse in Ancient Greek. When the 6-year-old von Neumann caught his mother staring aimlessly, he asked her, "What are you calculating?"Children did not begin formal schooling in Hungary until they were ten years of age. Max believed that knowledge of languages in addition to Hungarian was essential, so the children were tutored in English, French and Italian. By the age of 8, von Neumann was familiar with differential and integral calculus, but he was interested in history, he read his way through Wilhelm Oncken's 46-volume Allgemeine Geschichte in Einzeldarstellungen. A copy was contained in a private library. One of the rooms in the apartment was converted into a library and reading room, with bookshelves from ceiling to floor. Von Neumann entered the Lutheran Fasori Evangélikus Gimnázium in 1911. Eugene Wigner soon became his friend; this was one of the best schools in Budapest and was part of a brilliant education system designed for the elite.
Under the Hungarian system, children received all their education at the one gymnasium. The Hungarian school system produced a generation noted for intellectual achie
Moore School of Electrical Engineering
The Moore School of Electrical Engineering at the University of Pennsylvania came into existence as a result of an endowment from Alfred Fitler Moore on June 4, 1923. It was granted to Penn's School of Electrical Engineering, located in the Towne Building; the first dean of the Moore School was Harold Pender. The Moore School is famed as the birthplace of the computer industry: It was here that the first general-purpose Turing complete digital electronic computer, the ENIAC, was built between 1943 and 1946. Preliminary design work on the ENIAC's successor machine the EDVAC resulted in the stored program concept used in all computers today, the logical design having been promulgated in John von Neumann's First Draft of a Report on the EDVAC, a set of notes synthesized from meetings he attended at the Moore School; the first computer course was given at the Moore School in Summer 1946, leading to an explosion in computer development all over the world. Moore School faculty John Mauchly and J. Presper Eckert founded the first computer company, which produced the UNIVAC computer.
The Moore School has been integrated into Penn's School of Applied Science. It no longer exists as a separate entity. Constructed in 1921 as a two-story building by Erskin & Morris, it was renovated in 1926 by Paul Philippe Cret and a third story was added in 1940 by Alfred Bendiner. A complete history for all of Penn Engineering, including the Moore School
Magnetic tape
Magnetic tape is a medium for magnetic recording, made of a thin, magnetizable coating on a long, narrow strip of plastic film. It was developed in Germany based on magnetic wire recording. Devices that record and play back audio and video using magnetic tape are tape recorders and video tape recorders respectively. A device that stores computer data on magnetic tape is known as a tape drive. Magnetic tape revolutionized reproduction and broadcasting, it allowed radio, which had always been broadcast live, to be recorded for or repeated airing. It allowed gramophone records to be recorded in multiple parts, which were mixed and edited with tolerable loss in quality, it was a key technology in early computer development, allowing unparalleled amounts of data to be mechanically created, stored for long periods, accessed. In recent decades, other technologies have been developed that can perform the functions of magnetic tape. In many cases, these technologies have replaced tape. Despite this, innovation in the technology continues, Sony and IBM continue to produce new magnetic tape drives.
Over time, magnetic tape made in the 1970s and 1980s can suffer from a type of deterioration called sticky-shed syndrome. It can render the tape unusable; the oxide side of a tape is the surface. This is the side that stores the information, the opposite side is a substrate to give the tape strength and flexibility; the name originates from the fact that the magnetic side of most tapes is made of iron oxide, though chromium is used for some tapes. An adhesive binder between the oxide and the substrate holds the two sides together. In all tape formats, a tape drive uses motors to wind the tape from one reel to another, passing over tape heads to read, write or erase as it moves. Magnetic tape was invented for recording sound by Fritz Pfleumer in 1928 in Germany, based on the invention of magnetic wire recording by Oberlin Smith in 1888 and Valdemar Poulsen in 1898. Pfleumer's invention used a ferric oxide powder coating on a long strip of paper; this invention was further developed by the German electronics company AEG, which manufactured the recording machines and BASF, which manufactured the tape.
In 1933, working for AEG, Eduard Schuller developed the ring-shaped tape head. Previous head designs were tended to shred the tape. Another important discovery made in this period was the technique of AC biasing, which improved the fidelity of the recorded audio signal by increasing the effective linearity of the recording medium. Due to the escalating political tensions, the outbreak of World War II, these developments in Germany were kept secret. Although the Allies knew from their monitoring of Nazi radio broadcasts that the Germans had some new form of recording technology, its nature was not discovered until the Allies acquired captured German recording equipment as they invaded Europe at the end of the war, it was only after the war that Americans Jack Mullin, John Herbert Orr, Richard H. Ranger, were able to bring this technology out of Germany and develop it into commercially viable formats. A wide variety of recorders and formats have been developed since, most reel-to-reel and Compact Cassette.
The practice of recording and editing audio using magnetic tape established itself as an obvious improvement over previous methods. Many saw the potential of making the same improvements in recording the video signals used by television. Video signals use more bandwidth than audio signals. Existing audio tape recorders could not capture a video signal. Many set to work on resolving this problem. Jack Mullin and the BBC both created crude working systems that involved moving the tape across a fixed tape head at high speeds. Neither system saw much use, it was the team at Ampex, led by Charles Ginsburg, that made the breakthrough of using a spinning recording head and normal tape speeds to achieve a high head-to-tape speed that could record and reproduce the high bandwidth signals of video. The Ampex system was called Quadruplex and used 2-inch-wide tape, mounted on reels like audio tape, which wrote the signal in what is now called transverse scan. Improvements by other companies Sony, led to the development of helical scan and the enclosure of the tape reels in an easy-to-handle videocassette cartridge.
Nearly all modern videotape systems use helical cartridges. Videocassette recorders used to be common in homes and television production facilities, but many functions of the VCR have been replaced with more modern technology. Since the advent of digital video and computerized video processing, optical disc media and digital video recorders can now perform the same role as videotape; these devices offer improvements like random access to any scene in the recording and the ability to pause a live program and have replaced videotape in many situations. Magnetic tape was first used to record computer data in 1951 on the Eckert-Mauchly UNIVAC I; the system's UNISERVO I tape drive used a thin strip of one half inch wide metal, consisting of nickel-plated bronze. Recording density was 100 characters per inch on eight tracks. Early IBM 7 track tape drives were floor-standing and used vacuum columns to mechanically buffer long U-shaped loops of tape; the two tape reels visibly fed tape through the columns, intermittently spinning the reels in rapid, unsynchronized bursts, resulting in visually striking action.
Stock shots of such vacuum-column tape drives in motion were used to represent "the computer" in movies and televis
