Long and short scales
Thus, billion means a million millions, trillion means a million billions, and so on. Short scale Every new term greater than million is one thousand times larger than the previous term, billion means a thousand millions, trillion means a thousand billions, and so on. For whole numbers less than a million the two scales are identical. From a thousand million up the two scales diverge, using the words for different numbers, this can cause misunderstanding. Countries where the scale is currently used include most countries in continental Europe and most French-speaking, Spanish-speaking. The short scale is now used in most English-speaking and Arabic-speaking countries, in Brazil, in former Soviet Union, number names are rendered in the language of the country, but are similar everywhere due to shared etymology. Some languages, particularly in East Asia and South Asia, have large number naming systems that are different from both the long and short scales, for example the Indian numbering system.
After several decades of increasing informal British usage of the scale, in 1974 the government of the UK adopted it. With very few exceptions, the British usage and American usage are now identical, the first recorded use of the terms short scale and long scale was by the French mathematician Geneviève Guitel in 1975. At and above a million the same names are used to refer to numbers differing by a factor of an integer power of 1,000. Each scale has a justification to explain the use of each such differing numerical name. The short-scale logic is based on powers of one thousand, whereas the long-scale logic is based on powers of one million, in both scales, the prefix bi- refers to 2 and tri- refers to 3, etc. However only in the scale do the prefixes beyond one million indicate the actual power or exponent. In the short scale, the prefixes refer to one less than the exponent, the word, derives from the Old French, from the earlier Old Italian, milione, an intensification of the Latin word, mille, a thousand.
That is, a million is a big thousand, much as a great gross is a dozen gross or 12×144 =1728, the word, milliard, or its translation, is found in many European languages and is used in those languages for 109. However, it is unknown in American English, which uses billion, and not used in British English, which preferred to use thousand million before the current usage of billion. The financial term, which derives from milliard, is used on financial markets, as, unlike the term, billion, it is internationally unambiguous and phonetically distinct from million. Likewise, many long scale use the word billiard for one thousand long scale billions
Library of Congress
The Library of Congress is the research library that officially serves the United States Congress and is the de facto national library of the United States. It is the oldest federal cultural institution in the United States, the Library is housed in three buildings on Capitol Hill in Washington, D. C. it maintains the Packard Campus in Culpeper, which houses the National Audio-Visual Conservation Center. The Library of Congress claims to be the largest library in the world and its collections are universal, not limited by subject, format, or national boundary, and include research materials from all parts of the world and in more than 450 languages. Two-thirds of the books it acquires each year are in other than English. The Library of Congress moved to Washington in 1800, after sitting for years in the temporary national capitals of New York. John J. Beckley, who became the first Librarian of Congress, was two dollars per day and was required to serve as the Clerk of the House of Representatives.
The small Congressional Library was housed in the United States Capitol for most of the 19th century until the early 1890s, most of the original collection had been destroyed by the British in 1814, during the War of 1812. To restore its collection in 1815, the bought from former president Thomas Jefferson his entire personal collection of 6,487 books. After a period of growth, another fire struck the Library in its Capitol chambers in 1851, again destroying a large amount of the collection. The Library received the right of transference of all copyrighted works to have two copies deposited of books, maps and diagrams printed in the United States. It began to build its collections of British and other European works and it included several stories built underground of steel and cast iron stacks. Although the Library is open to the public, only high-ranking government officials may check out books, the Library promotes literacy and American literature through projects such as the American Folklife Center, American Memory, Center for the Book, and Poet Laureate.
James Madison is credited with the idea for creating a congressional library, part of the legislation appropriated $5,000 for the purchase of such books as may be necessary for the use of Congress. And for fitting up an apartment for containing them. Books were ordered from London and the collection, consisting of 740 books and 3 maps, was housed in the new Capitol, as president, Thomas Jefferson played an important role in establishing the structure of the Library of Congress. The new law extended to the president and vice president the ability to borrow books and these volumes had been left in the Senate wing of the Capitol. One of the only congressional volumes to have survived was a government account book of receipts and it was taken as a souvenir by a British Commander whose family returned it to the United States government in 1940. Within a month, former president Jefferson offered to sell his library as a replacement
A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or fraction of the unit. While all metric prefixes in use today are decadic, historically there have been a number of binary metric prefixes as well. Each prefix has a symbol that is prepended to the unit symbol. The prefix kilo-, for example, may be added to gram to indicate multiplication by one thousand, the prefix milli-, may be added to metre to indicate division by one thousand, one millimetre is equal to one thousandth of a metre. Decimal multiplicative prefixes have been a feature of all forms of the system with six dating back to the systems introduction in the 1790s. Metric prefixes have even been prepended to non-metric units, the SI prefixes are standardized for use in the International System of Units by the International Bureau of Weights and Measures in resolutions dating from 1960 to 1991. Since 2009, they have formed part of the International System of Quantities, the BIPM specifies twenty prefixes for the International System of Units.
Each prefix name has a symbol which is used in combination with the symbols for units of measure. For example, the symbol for kilo- is k, and is used to produce km, kg, and kW, which are the SI symbols for kilometre, prefixes corresponding to an integer power of one thousand are generally preferred. Hence 100 m is preferred over 1 hm or 10 dam, the prefixes hecto, deca and centi are commonly used for everyday purposes, and the centimetre is especially common. However, some building codes require that the millimetre be used in preference to the centimetre, because use of centimetres leads to extensive usage of decimal points. Prefixes may not be used in combination and this applies to mass, for which the SI base unit already contains a prefix. For example, milligram is used instead of microkilogram, in the arithmetic of measurements having units, the units are treated as multiplicative factors to values. If they have prefixes, all but one of the prefixes must be expanded to their numeric multiplier,1 km2 means one square kilometre, or the area of a square of 1000 m by 1000 m and not 1000 square metres.
2 Mm3 means two cubic megametres, or the volume of two cubes of 1000000 m by 1000000 m by 1000000 m or 2×1018 m3, and not 2000000 cubic metres, examples 5 cm = 5×10−2 m =5 ×0.01 m =0. The prefixes, including those introduced after 1960, are used with any metric unit, metric prefixes may be used with non-metric units. The choice of prefixes with a unit is usually dictated by convenience of use. Unit prefixes for amounts that are larger or smaller than those actually encountered are seldom used
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, 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
Hard disk drive
The platters are paired with magnetic heads, usually arranged on a moving actuator arm, which read and write data to the platter surfaces. Data is accessed in a manner, meaning that individual blocks of data can be stored or retrieved in any order. HDDs are a type of storage, retaining stored data even when powered off. Introduced by IBM in 1956, HDDs became the dominant secondary storage device for computers by the early 1960s. Continuously improved, HDDs have maintained this position into the era of servers. More than 200 companies have produced HDDs historically, though after extensive industry consolidation most current units are manufactured by Seagate, Toshiba, as of 2016, HDD production is growing, although unit shipments and sales revenues are declining. While SSDs have higher cost per bit, SSDs are replacing HDDs where speed, power consumption, small size, the primary characteristics of an HDD are its capacity and performance. Capacity is specified in unit prefixes corresponding to powers of 1000, the two most common form factors for modern HDDs are 3. 5-inch, for desktop computers, and 2. 5-inch, primarily for laptops.
HDDs are connected to systems by standard interface cables such as PATA, SATA, Hard disk drives were introduced in 1956, as data storage for an IBM real-time transaction processing computer and were developed for use with general-purpose mainframe and minicomputers. The first IBM drive, the 350 RAMAC in 1956, was approximately the size of two medium-sized refrigerators and stored five million six-bit characters on a stack of 50 disks. In 1962 the IBM350 RAMAC disk storage unit was superseded by the IBM1301 disk storage unit, cylinder-mode read/write operations were supported, and the heads flew about 250 micro-inches above the platter surface. Motion of the head array depended upon a binary system of hydraulic actuators which assured repeatable positioning. The 1301 cabinet was about the size of three home refrigerators placed side by side, storing the equivalent of about 21 million eight-bit bytes, access time was about a quarter of a second. Also in 1962, IBM introduced the model 1311 disk drive, users could buy additional packs and interchange them as needed, much like reels of magnetic tape.
Later models of removable pack drives, from IBM and others, became the norm in most computer installations, non-removable HDDs were called fixed disk drives. Some high-performance HDDs were manufactured with one head per track so that no time was lost physically moving the heads to a track, known as fixed-head or head-per-track disk drives they were very expensive and are no longer in production. In 1973, IBM introduced a new type of HDD code-named Winchester and its primary distinguishing feature was that the disk heads were not withdrawn completely from the stack of disk platters when the drive was powered down. Instead, the heads were allowed to land on an area of the disk surface upon spin-down
A motherboard is the main printed circuit board found in general purpose microcomputers and other expandable systems. It holds and allows communication between many of the electronic components of a system, such as the central processing unit and memory. In very old designs, copper wires were the discrete connections between card connector pins, but printed circuit boards soon became the standard practice, the Central Processing Unit and peripherals were housed on individual printed circuit boards, which were plugged into the backplate. The ubiquitous S-100 bus of the 1970s is an example of type of backplane system. During the late 1980s and 1990s, it became economical to move a number of peripheral functions onto the motherboard. Business PCs, and servers were more likely to need expansion cards, either for more robust functions, or for higher speeds and notebook computers that were developed in the 1990s integrated the most common peripherals. This even included motherboards with no upgradeable components, a trend that would continue as smaller systems were introduced after the turn of the century, processors, network controllers, power source, and storage would be integrated into some systems. A motherboard provides the connections by which the other components of the system communicate.
Unlike a backplane, it contains the central processing unit and hosts other subsystems. A typical desktop computer has its microprocessor, main memory, an important component of a motherboard is the microprocessors supporting chipset, which provides the supporting interfaces between the CPU and the various buses and external components. This chipset determines, to an extent, the features and capabilities of the motherboard, modern motherboards include, Sockets in which one or more microprocessors may be installed. In the case of CPUs in ball grid array packages, such as the VIA C3, as of 2007, some graphics cards require more power than the motherboard can provide, and thus dedicated connectors have been introduced to attach them directly to the power supply. Connectors for hard drives, typically SATA only, disk drives connect to the power supply. Additionally, nearly all motherboards include logic and connectors to support commonly used devices, such as USB for mouse devices. Early personal computers such as the Apple II or IBM PC included only this minimal peripheral support on the motherboard, occasionally video interface hardware was integrated into the motherboard, for example, on the Apple II and rarely on IBM-compatible computers such as the IBM PC Jr.
Additional peripherals such as disk controllers and serial ports were provided as expansion cards, given the high thermal design power of high-speed computer CPUs and components, modern motherboards nearly always include heat sinks and mounting points for fans to dissipate excess heat. Motherboards are produced in a variety of sizes and shapes called computer form factor, the motherboards used in IBM-compatible systems are designed to fit various case sizes. As of 2007, most desktop computer motherboards use the ATX standard form factor — even those found in Macintosh and Sun computers, a cases motherboard and PSU form factor must all match, though some smaller form factor motherboards of the same family will fit larger cases
The megabyte is a multiple of the unit byte for digital information. Its recommended unit symbol is MB, but sometimes MByte is used, the unit prefix mega is a multiplier of 1000000 in the International System of Units. Therefore, one megabyte is one million bytes of information and this definition has been incorporated into the International System of Quantities. However, in the computer and information fields, several other definitions are used that arose for historical reasons of convenience. A common usage has been to one megabyte as 1048576bytes. However, most standards bodies have deprecated this usage in favor of a set of binary prefixes, less common is a convention that used the megabyte to mean 1000×1024 bytes. The megabyte is commonly used to measure either 10002 bytes or 10242 bytes, the interpretation of using base 1024 originated as a compromise technical jargon for the byte multiples that needed to be expressed by the powers of 2 but lacked a convenient name. As 1024 approximates 1000, roughly corresponding to the SI prefix kilo-, in 1998 the International Electrotechnical Commission proposed standards for binary prefixes requiring the use of megabyte to strictly denote 10002 bytes and mebibyte to denote 10242 bytes.
By the end of 2009, the IEC Standard had been adopted by the IEEE, EU, ISO, the Mac OS X10.6 file manager is a notable example of this usage in software. Since Snow Leopard, file sizes are reported in decimal units, base 21 MB =1048576 bytes is the definition used by Microsoft Windows in reference to computer memory, such as RAM. This definition is synonymous with the binary prefix mebibyte. Mixed 1 MB =1024000 bytes is the used to describe the formatted capacity of the 1.44 MB3. 5inch HD floppy disk. Semiconductor memory doubles in size for each address lane added to an integrated circuit package, the capacity of a disk drive is the product of the sector size, number of sectors per track, number of tracks per side, and the number of disk platters in the drive. Changes in any of these factors would not usually double the size, sector sizes were set as powers of two for convenience in processing. It was an extension to give the capacity of a disk drive in multiples of the sector size, giving a mix of decimal.
Depending on compression methods and file format, a megabyte of data can roughly be, a 4 megapixel JPEG image with normal compression. Approximately 1 minute of 128 kbit/s MP3 compressed music,6 seconds of uncompressed CD audio. A typical English book volume in plain text format, the human genome consists of DNA representing 800 MB of data
The encoding material sits atop a thicker substrate which makes up the bulk of the disc and forms a dust defocusing layer. The encoding pattern follows a continuous, spiral path covering the disc surface. Most optical discs exhibit a characteristic iridescence as a result of the diffraction grating formed by its grooves and this side of the disc contains the actual data and is typically coated with a transparent material, usually lacquer. The reverse side of a disc usually has a printed label, sometimes made of paper. Optical discs are usually between 7.6 and 30 cm in diameter, with 12 cm being the most common size, a typical disc is about 1.2 mm thick, while the track pitch ranges from 1.6 µm to 320 nm. An optical disc is designed to support one of three recording types, read-only, recordable, or re-recordable, write-once optical discs commonly have an organic dye recording layer between the substrate and the reflective layer. Rewritable discs typically contain an alloy recording layer composed of a phase change material, most often AgInSbTe, an alloy of silver, antimony, Optical discs are most commonly used for storing music, video, or data and programs for personal computers.
The Optical Storage Technology Association promotes standardized optical storage formats, although optical discs are more durable than earlier audio-visual and data storage formats, they are susceptible to environmental and daily-use damage. Libraries and archives enact optical media preservation procedures to ensure continued usability in the optical disc drive or corresponding disc player. For computer data backup and physical data transfer, optical discs such as CDs and DVDs are gradually being replaced with faster, smaller solid-state devices and this trend is expected to continue as USB flash drives continue to increase in capacity and drop in price. Additionally, music purchased or shared over the Internet has significantly reduced the number of audio CDs sold annually. The first recorded use of an optical disc was in the 1884 when Alexander Graham Bell, Chichester Bell. An early optical disc system existed in 1935, named Lichttonorgel, an early analog optical disc used for video recording was invented by David Paul Gregg in 1958 and patented in the US in 1961 and 1969.
This form of optical disc was an early form of the DVD. It is of special interest that U. S, patent 4,893,297, filed 1989, issued 1990, generated royalty income for Pioneer Corporations DVA until 2007 —then encompassing the CD, DVD, and Blu-ray systems. In the early 1960s, the Music Corporation of America bought Greggs patents and his company, american inventor James T. Russell has been credited with inventing the first system to record a digital signal on an optical transparent foil which is lit from behind by a high-power halogen lamp. Russells patent application was first filed in 1966 and he was granted a patent in 1970, following litigation and Philips licensed Russells patents in the 1980s. Both Greggs and Russells disc are floppy media read in transparent mode, in the Netherlands in 1969, Philips Research physicist, Pieter Kramer invented an optical videodisc in reflective mode with a protective layer read by a focused laser beam U. S
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, tens, 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 the anatomical term for fingers and toes. In English, decimal means tenth, decimate means reduce by a tenth, 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
A supercomputer is a computer with a high level of computing performance compared to a general-purpose computer. Performance of a supercomputer is measured in floating-point operations per second instead of instructions per second. As of 2015, there are supercomputers which can perform up to quadrillions of FLOPS and it tops the rankings in the TOP500 supercomputer list. Sunway TaihuLights emergence is notable for its use of indigenous chips, as of June 2016, for the first time, had more computers on the TOP500 list than the United States. However, U. S. built computers held ten of the top 20 positions, in November 2016 the U. S. has five of the top 10, throughout their history, they have been essential in the field of cryptanalysis. The use of multi-core processors combined with centralization is an emerging trend, the history of supercomputing goes back to the 1960s, with the Atlas at the University of Manchester and a series of computers at Control Data Corporation, designed by Seymour Cray.
These used innovative designs and parallelism to achieve superior computational peak performance, Cray left CDC in 1972 to form his own company, Cray Research. Four years after leaving CDC, Cray delivered the 80 MHz Cray 1 in 1976, the Cray-2 released in 1985 was an 8 processor liquid cooled computer and Fluorinert was pumped through it as it operated. It performed at 1.9 gigaflops and was the second fastest after M-13 supercomputer in Moscow. Fujitsus Numerical Wind Tunnel supercomputer used 166 vector processors to gain the top spot in 1994 with a speed of 1.7 gigaFLOPS per processor. The Hitachi SR2201 obtained a performance of 600 GFLOPS in 1996 by using 2048 processors connected via a fast three-dimensional crossbar network. The Intel Paragon could have 1000 to 4000 Intel i860 processors in various configurations, the Paragon was a MIMD machine which connected processors via a high speed two dimensional mesh, allowing processes to execute on separate nodes, communicating via the Message Passing Interface.
Approaches to supercomputer architecture have taken dramatic turns since the earliest systems were introduced in the 1960s, early supercomputer architectures pioneered by Seymour Cray relied on compact innovative designs and local parallelism to achieve superior computational peak performance. However, in time the demand for increased computational power ushered in the age of massively parallel systems, supercomputers of the 21st century can use over 100,000 processors connected by fast connections. The Connection Machine CM-5 supercomputer is a parallel processing computer capable of many billions of arithmetic operations per second. Throughout the decades, the management of heat density has remained a key issue for most centralized supercomputers, the large amount of heat generated by a system may have other effects, e. g. reducing the lifetime of other system components. There have been diverse approaches to management, from pumping Fluorinert through the system. Systems with a number of processors generally take one of two paths
Approaches to supercomputer architecture have taken dramatic turns since the earliest systems were introduced in the 1960s. Early supercomputer architectures pioneered by Seymour Cray relied on compact innovative designs, however, in time the demand for increased computational power ushered in the age of massively parallel systems. Supercomputers of the 21st century can use over 100,000 processors connected by fast connections, throughout the decades, the management of heat density has remained a key issue for most centralized supercomputers. The large amount of heat generated by a system may have other effects, there have been diverse approaches to heat management, from pumping Fluorinert through the system, to a hybrid liquid-air cooling system or air cooling with normal air conditioning temperatures. In another approach, a number of processors are used in close proximity to each other. Since the late 1960s the growth in the power and proliferation of supercomputers has been dramatic, throughout the decades, the management of heat density has remained a key issue for most centralized supercomputers.
Seymour Crays get the heat out motto was central to his philosophy and has continued to be a key issue in supercomputer architectures. The large amount of heat generated by a system may have other effects, the heat from the Aquasar supercomputer is used to warm a university campus. g. in a computer cluster, or could be geographically dispersed in grid computing. As the number of processors in a supercomputer grows, component failure rate begins to become a serious issue, if a supercomputer uses thousands of nodes, each of which may fail once per year on the average, the system will experience several node failures each day. As the price/performance of general purpose graphic processors has improved, a number of supercomputers such as Tianhe-I. However, GPUs are gaining ground and in 2012 the Jaguar supercomputer was transformed into Titan by replacing CPUs with GPUs. As the number of independent processors in a supercomputer increases, the way they access data in the system and how they share.
Over the years a number of systems for distributed file management were developed, e. g. the IBM General Parallel File System, BeeGFS, a number of supercomputers on the TOP100 list such as the Tianhe-I use Linuxs Lustre file system. With the Minnesota FORTRAN compiler the 6600 could sustain 500 kiloflops on standard mathematical operations, in time, as the number of processors increased, different architectural issues emerged. Two issues that need to be addressed as the number of increases are the distribution of memory. In the distributed memory approach, each processor is physically packaged close with some local memory, the memory associated with other processors is further away based on bandwidth and latency parameters in non-uniform memory access. In the 1960s pipelining was viewed as an innovation, and by the 1970s the use of vector processors had been well established, by the 1980s, many supercomputers used parallel vector processors. The relatively small number of processors in early systems, allowed them to use a shared memory architecture
A tape drive is a data storage device that reads and writes data on a magnetic tape. Magnetic tape data storage is used for offline, archival data storage. Tape media generally has a unit cost and a long archival stability. A tape drive provides sequential access storage, unlike a hard disk drive, a disk drive can move to any position on the disk in a few milliseconds, but a tape drive must physically wind tape between reels to read any one particular piece of data. As a result, tape drives have very slow average seek times to data, tape drives can stream data very quickly off a tape when the required position has been reached. For example, as of 2010 Linear Tape-Open supported continuous data transfer rates of up to 140 MB/s, magnetic tape drives were first used for data storage on mainframe computers in the 1950s, with capacities less than one megabyte. As technology advanced, capacities increased to 10 terabytes or higher of uncompressed data per cartridge as of 2014, in early computer systems, magnetic tape might be the main storage medium, although the drives were expensive, the tapes were inexpensive.
The true storage capacity is known as the native capacity or the raw capacity. IBM and Sony have used higher compression ratios in their marketing materials, the compression ratio actually achievable depends on the data being compressed. Some data has little redundancy, large files, for example, already use compression technology. A sparse database, on the hand, may allow compression ratios better than 10,1. Tape drives can be connected to a computer with SCSI, Fibre Channel, SATA, USB, FireWire, FICON, or other interfaces. Tape drives are used with autoloaders and tape libraries which automatically load, unload, in the early days of home computing and hard disk drives were very expensive. Many computers had an interface to store data via a tape recorder. Simple dedicated tape drives, such as the professional DECtape and the home ZX Microdrive, the drop in disk drive prices made such alternatives obsolete. In this situation, the modern fast-running tape drive is unable to stop the tape instantly, the drive must decelerate and stop the tape, rewind it a short distance, restart it, position back to the point at which streaming stopped and resume the operation.
If the condition repeats, the resulting back-and-forth tape motion resembles that of shining shoes with a cloth, shoe-shining decreases the attainable data transfer rate and tape life, and tape capacity. In early tape drives, non-continuous data transfer was normal and unavoidable, computer processing power and amounts of available memory were usually insufficient to provide a constant stream, so tape drives were typically designed for so called start-stop operation