Difference Between Memory And Data Storage Computer Science Essay

Difference Between retrospect And Data stock board calculator Science EssayThe terms retentiveness and in bodation retention ar a great deal conf apply. Both retrospect and entropy terminus argon means by which a selective information processor keeps data used to perform tasks. Both of them are measured in bytes. The term repositing refers to the step of Random Access depot (RAM) yet similarly includes Read-Only retentivity ( fixed storage) installed in the data processor, whereas the term estimator entrepot refers to the qualification of the calculating machines hard disk.Figure 12 Difference between storage and Data StorageFor example, in figure 12, the file console table represents the calculators hard disk, which provides transshipment center for all the files and study we take in your office. When we exercise in to incline, we take out the files we need from warehousing and put them on our desk for blowsy access while we work on them. The desk is like reposition in the computer. It holds the training and data we need to collect handy while youre running(a)s.The of import(prenominal) exit between keeping and data storage is their enjoyment. Storage is used to hold all the computers information. Data terminald in the hard disk is permanent and it is not lose when the computer is turned off. When we delete a file, scarcely the access to that file is removed, not the information itself. To permanently delete a file, the hard disk moldiness be formatted or overwritten. It is raze possible that level(p) though a disk has been formatted, an expert fuel still view the information.Memory and data storage can work together. When the computer does not attain enough RAM to support its processes, it converts a portion of the hard disk into virtual holding. Virtual shop acts the same way RAM does. However, since it is a part of the hard disk, using virtual holding slows the computer obliterate.2.2 Internal Memory a nd External MemoryComputer internal storage is used to neckcloth data that is used by the constitution at startup and to run various oddballs of programs such as the run clay. Typically, internal recollection is contained on small micro take to the woodss that are either attached or connected to the computers motherboard. Computer entrepot can range from a equal of megabytes to several gigabytes. SRAM, DRAM, and ROM are the example of internal memory.External computer memory is technically any storage doojigger that we can connect to our computer to record data. Flash drives, HDD with USB cable, any SD card are the example of external memory.2.3 Hierarchy of StorageGenerally, the lower a storage is in the hierarchy, the lesser its bandwidth and the greater its access latency is from the mainframe computer. This traditional division of storage to primary, second-string, tertiary and off-line storage is also guided by cost per bit. Historically, memory has been called loa ding, main memory, unfeigned storage or internal memory while storage contrivances have been referred to as secondary storage, external memory or peripheral storage.2.3.1 Primary StorageIn computer memory the term primary storage or primary memory is used for the information in physical systems which function at high-speed as a difference from secondary storage. Primary storage often referred to simply as memory, is the only adept this instant accessible to the CPU. The CPU continuously submits instructions stored there and executes them as required. Main memory is directly or indirectly connected to the central processing unit via a memory bus. It is actually cardinal buses, an address bus and a data bus. The CPU set-back of allly sends a number through an address bus, a number called memory address that indicates the desired location of data. Then it get a lines or bring throughs the data itself using the data bus. Additionally, a memory management unit (MMU) is a small device between CPU and RAM recalculating the actual memory address, for example to provide an abstraction of virtual memory or other tasks.2.3.2 substitute StorageSecondary storage or secondary memory is physical devices for program and data storage which are slow to access but offer high memory capacity. It differs from primary storage in that it is not directly accessible by the CPU. The computer usually uses its input/output channels to access secondary storage and transfers the desired data using intermediate area in primary storage. Secondary storage does not lose the data when the device is queened down because it is non-volatile. In modern computers, hard disk drives are usually used as secondary storage and it is typically about a million propagation slower than memory. Some other examples of secondary storage technologies are USB flash drives, floppy disks, magnetic tape, paper tape, punched cards, standalone RAM disks, and Iomega Zip drives.2.3.3 third storageTertiary storage or tertiary memory provides a third level of storage. Typically it involves a robotic mechanism which willing mount and dismount removable bay window storage media into a storage device according to the systems demands, these data are often copied to secondary storage before use. It is much slower than secondary storage. This is earlier useful for extraordinarily large data stores, accessed without human operators. When a computer needs to read information from the tertiary storage, it will first consult a catalog database to determine which tape or disc contains the information and then the computer will instruct a robotic arm to fetch the specialty and fundament it in a drive. When the computer has finished reading the information, the robotic arm will return the medium to its place in the library.2.3.4 off-line storageOff-line storage is computer data storage on a medium or a device that is not under the control of a processing unit. The medium is recorded, usually in a secondary or tertiary storage device and then physically removed or disconnected. It must be inserted or connected by a human operator before a computer can access it again. Unlike tertiary storage, it cannot be accessed without human interaction.Off-line storage is used to transfer information. Additionally, in case a disaster like a fire destroys the original data, a medium in a remote location will probably be unaffected, enabling disaster recovery.In modern personal computers, intimately secondary and tertiary storage media are also used for off-line storage. optical discs and flash memory devices are close to popular, and to much lesser extent removable hard disk drives. In enterprise uses, magnetic tape is predominant. Older examples are floppy disks, Zip disks, or punched cards.2.4 Characteristics of Storage2.4.1 VolatilityVolatile memory is computer memory that requires power to maintain the stored information and non-volatile memory is computer memory that can ret ain the stored information even when not powered. That is why the contents of RAM are erased when the power of the computer is turned off but ROM holds its data indefinitely. The fastest memory technologies of today are volatile ones. Non-volatile memory is suitable for long-term storage of information.2.4.2 MutabilityRead/write storage or mutable storage allows information to be overwritten at any prison term. A computer without many step of read/write storage for primary storage purposes would be useless for many tasks. Modern computers typically use read/write storage also for secondary storage.Read only storage retains the information stored at the time of manufacture, and allows the information to be written only once at some pull down after manufacture. These are called immutable storage. Immutable storage is used for tertiary and off-line storage. Examples include CD-ROM and CD-R.Slow write, fast read storage is the read/write storage which allows information to be overwr itten multiple times, but with the write operation existence much slower than the read operation. Examples include CD-RW and flash memory.2.4.3 accessibilityIn random access, any location in storage can be accessed at any moment in approximately the same amount of time. Such characteristic is well suited for primary and secondary storage. Most semiconductor unit memories and disk drives provide random access.In sequential access, the accessing of pieces of information will be in a serial order, one after the other, therefore the time to access a particular piece of information depends upon which piece of information was last accessed. Such characteristic is typical of off-line storage.2.4.4 AddressabilityIn modern computers, location-addressable storage usually limits to primary storage. Each individually accessible unit of information in storage is selected with its numerical memory address.In modern computers, secondary, tertiary and off-line storage use files addressable system s. schooling is divided into files of variable length, and a particular file is selected with human-readable directory and file names.Content-addressable storage can be implemented using software or hardware, hardware being faster but more(prenominal) expensive option. Each individually accessible unit of information is selected based on the basis of the contents stored there.2.4.5 CapacityThe total amount of stored information that a storage device or medium can hold is raw capacity.Memory storage density is a measure of the quantity of information bits that can be stored on a given length of track, area of surface, or in a given volume of a computer storage medium. Generally, higher(prenominal) density is more desirable, for it allows greater volumes of data to be stored in the same physical length. Density therefore has a direct relationship to storage capacity of a given medium.2.4.6 PerformanceLatency is a measure of time delay experienced in a system, the precise definition of which depends on the system and the time being measured. The time it takes to access a particular location in storage. The relevant unit of measurement is typically nanosecond for primary storage, millisecond for secondary storage, and second for tertiary storage. It may make sense to separate read latency and write latency, and in case of sequential access storage, minimum, maximum and mediocre latency.In communication networks, such as Ethernet or packet radio, throughput or network throughput is the average rate of successful message delivery over a communication channel. In computer data storage, throughput is usually expressed in terms of megabytes per second, though bit rate may also be used. As with latency, read rate and write rate may need to be differentiated. Also accessing media sequentially, as opposed to randomly, typically yields maximum throughput.2.5 Fundamental Storage TechnologiesThe most commonly used data storage technologies are semiconductor, magnetic, an d optical, while paper still sees some limited usage. Some other fundamental storage technologies have also been used in the past or are proposed for knowledge.2.5.1 SemiconductorSemiconductor memory is an electronic data storage device, often used as computer memory, implemented on a semiconductor-based integrated circuit. A semiconductor memory chip may contain millions of tiny transistors or capacitors. It is made in many different types and technologies.Semiconductor memory has the property of random access, which means that it takes the same amount of time to access any memory location. Semiconductor memory also has much faster access times than other types of data storage. A byte of data can be written to or read from semiconductor memory at heart a few nanoseconds, while access time for rotating storage such as hard disks is in the range of milliseconds. For these reasons it is used for main computer memory or primary storage, to hold data the computer is currently working on, among other uses.2.5.2 MagneticMagnetic storage uses different patterns of magnetisation on a magnetically coated surface to store information. Magnetic storage is non-volatile. The information is accessed using one or more read/write heads which may contain one or more recording transducers. A read/write head only covers a part of the surface so that the head or medium or both must be moved relative to another in order to access data.2.5.3 OpticalOptical storage is a term from engineering referring to the Storage of data on an optically readable medium. Data is recorded by making marks in a pattern that can be read back with the aid of light, usually a beam of laser light precisely focused on a spinning disc. An older example, that does not require the use of computers, is microform.2.5.4 PaperPaper data storage refers to the use of paper as a data storage device. This includes writing, illustrating, and the use of data that can be interpreted by a machine or is the result of t he functioning of a machine. Paper data storage, typically in the form of paper tape or punched cards, has long been used to store information for automatic processing, particularly before general-purpose computers existed. Information was recorded by punching holes into the paper or cardboard medium and was read mechanically to determine whether a particular location on the medium was secure or contained a holeApr 142Computer Organization and ArchitectureFacebookTwitterGoogleTumblrComputer MemoryChapter 1 Introduction to Computer MemoryFigure 1 An Imaginary Computer MemoryTo know about the detail of computer memory, first of all we should know what is memory? and then what is computer memory?.As we know the memory is a power to remember things. In psychology, memory is the process by which information is encoded, stored, and retrieved. But in computing, memory refers to the physical devices used to store programs or data on a temporary or permanent basis for use in a computer or o ther digital electronic device.Computer data storage, often called storage or memory. It is a core function and fundamental component of computers. A computers memory can be said as a list of cells into which numbers can be placed or read. Each cell has a numbered address and can store a single number. In almost all modern computers, each memory cell is set up to store binary star numbers in groups of eight bits. A bit is the basic unit of information in computing and telecommunications. A bit can have only two values, either 1 or 0. Eight bits form a byte. Each byte is able to represent 256 different numbers either from 0 to 255 or 128 to +127. To store larger numbers several consecutive bytes typically two, four or eight may be used. When negative numbers are required they are usually stored in tows complement notation which is a mathematical operation on binary numbers.A computer can store any kind of information in memory if it can be represented numerically. The information st ored in memory may represent possiblely anything. Letters, numbers, even computer instructions can be placed into memory with equal ease. A computer consists of at least one processing element, typically a central processing unit (CPU) and some form of memory. Since the CPU does not differentiate between different types of data, it is the softwares responsibility to give significance to what the memory sees as nothing but a series of numbers.Modern computers have billions or even trillions of bytes of memory. In computer architecture, the CPU contains a special set of memory cells which is called registers. A processor register can be read and written too much faster than the main memory area. Registers are used for the most frequently needed data items to avoid having to access main memory every time data is needed.1.1 First Computer MemoryThe first computers were often very large, usually as big as a desk or even a room and had minimal processing capability. These early computers were built to work on specific problems or solve certain types of equations and not much more.The first computers used punch cards for input and had very limited memory for processing. The average memory in the first computers was between three and twoscore five kilo-bits Memory was used to store data in the processing of analog equations, and the results were then printed in binary.When compared to the computers available today, the first computers do not seem very technologically advanced, but at the time they were created these first computers were engineering masterpieces. legion(predicate) of the concepts created when building early computers are still in use in modern computing technology.The Atanasoff Berry Computer (ABC) credited with being the very first computer. The ABC had a whopping 3000 bits of memory which allowed it to process sixty items at one time. Other early computers had more memory. Some has high as forty five kilobits, which allowed them to process severa l more words of data in a shorter amount of time increasing the overall processing speed of the system.Without the first computers and their ability to make mere(a) calculations, the technology we use today might not be as advanced as it has become.1.2 History of Computer MemoryIn 1940s memory technology for the most part permitted few bytes capacity. The first electronic programmable digital computer the ENIAC (ElectronicNumericalIntegratorandComputer) using thousands of octal base radio hoover tubes. In electronics, a vacuumtube is a device controlling electric current through a vacuum in a sealed container. The ENIAC could perform simple calculations involving 20 numbers of ten decimal digits which were held in the vacuum tube accumulators.The next significant advance in computer memory delaylinememory. It was a form of computer memory used on some of the earliest digital computers. comparable many modern forms of electronic computer memory, delay line memory was a refreshabl e memory but it was opposed to modern random access memory. Delay line memory was sequential access. Delay lines could store bits of information within a quartz and transfer it through sound waves propagating through mercury. Delay line memory would be limited to a capacity of up to a few hundred thousand bits to remain efficient.In 1946 two alternatives to the delay line, the Williams tube and Selectron tube, both using electron beams in glass tubes for storage. The Williams tube would boot out more capacious than the Selectron tube because the Selectron was limited to 256 bits, while the Williams tube could store thousands. It was also less expensive than Selectron tube.To find non-volatile memory Jay Forrester, Jan A. Rajchman and An Wang developed magnetic core memory in the late 1940s. It was allowed for recall of memory after power loss. Magnetic core memory would become the dominant form of memory until the development of transistor-based memory in the late 1960s.1.2. 1 Hist orical Development of Computer MemoryComputer memory is much more than DRAM or Flash. It has come a long way up until the origins of todays omnipresent memory technologies. If we take it more than 160 years back in time and revisit the milestones of computer memory technology then products we may have never heard of.1.2.1.1 hit CardsFigure 2 Punch CardsApunched card is a piece ofstiff paper that contains digital information represented by the presence or absence of holes in predefined positions. Earlydigital computers used punched cards as the primary medium for input of bothcomputer programs anddata. In 1837 Charles Babbage first purposed the Analytical Engine, which was the first computer to use punch cards as memory and a way to program the computer. Punch cards also known as Hollerith cardsand IBM cardsare paper cards containing several punched holes that where originally punched by hand and later by computers that represent data. Hollerithspunchcardsused in the 1890 number ha d round holes, 12 speechs and 24 columns. The IBMpunchedcard designed in 1928, had rectangular holes, 80 columns with 12 punch locations and each one character to each column. So 80 x 12 = 960, this gives us a maximum capacity of 960 bits or 125 bytes of data. The use of punch cards predates computers. They were used as early as 1725 in the textile industry for controlling mechanized textile looms. From the 1900s, into the 1950s, punched cards were the primary medium for data entry,data storage, and processing in institutional computing. As of 2012, some voting machinesstill utilize punched cards to input data. During the 1960s, the punched card was gradually replaced by magnetic tape.1.2.1.2 Drum MemoryFigure 3 DrumMemoryDrummemory is an obsolete magnetic data storage device. A stick is a large metal cylinder that is coated on the outside surface with a ferromagnetic recording material. It could be considered the precursor to the hard disk platter, but in the form of a drum rath er than a flat disk. In most cases a row of fixed read-write heads runs along the long axis of the drum, one for each track. The drums of the Atanasoff-Berry Computer stored information using regenerative capacitor memory. Regenerativecapacitormemory is a type of computer memory that uses the electric property of capacitance to store the bits of data. A difference between most drums and a modern hard disk drive is that on a drum there was a track per head so that the heads do not have to move to the track to access data. Head per track disks were used mostly for paging. Particularly while drums were used as main working memory, programmers often took to positioning code onto the drum in such a way as to reduce the amount of time needed to find the next instruction. In 1932 Austrian IT engineer Gustav Tauschek invented the first widely used computer memory, called drum memory. In 1942 John Atanasoff successfully tests the Atanasoff-Berry Computer (ABC) which was the first computer to use regenerative capacitor drum memory. It was widely used in the 1950s and 60s as the main working memory of computers. Tauscheks original drum memory had a capacity of about 500,000 bits or 62.5 kilobytes. One of the early ken-produced computers, IBM 650, had about 8.5 kilobytes of drum memory, which in a later model was doubled to about 17 kilobytes. Some drum memories were also used as secondary storage. Drums were later replaced as the main working memory by memory such as core memory.1.2.1.3 Williams TubeFigure 4 Williams TubeFreddie Williams applies for a patent on his cathode-ray tube (CRT) storing device in 1946. The device that later became known as the Williams tube or Williams- Kilburn tube. It was used as a computer memory to electronically store binary data. It was the first random-access digital storage device. The Williams tube depends on an effect called secondary emission. When a spatter is drawn on a cathode ray tube, the area of the dot becomes slightly positi vely vote downd and the area immediately around it becomes slightly negatively charged, creating a charge well which is unable to convert to another type of energy. The charge well remains on the surface of the tube for a fraction of a second, allowing the device to act as a computer memory. The charge well lifetime depends on the electrical resistance of the inside of the tube.By drawing a second dot immediately next to the first one the dot can be erased. Information is read from the tube by means of a metal pickup plate that covers the face of the tube. Each time a dot is created or erased, the change in electrical charge induces a voltage pulse in the pickup plate. There is no practical restriction in the order of positions so it is called random-access nature of the lookup.Reading a memory location creates a new charge well, destroying the original contents of that location, and so any read has to be followed by a write to reinstate the original data. Since the charge graduall y leaked away, it was necessary to scan the tube periodically and revisal every dot.Some Williams tubes were made from radar-type cathode ray tubes with a phosphor coating that made the data visible. Each Williams tube could store about 512-1024 bits of data.1.2.1.4 Selectron TubeFigure 5 Selectron TubeBetween 1946 and 1953 Jan Rajchman begins his work on developing the Selectron tube. The original 4096-bit Selectron was a large, 5 inch by 3 inch vacuum tube with a cathode running up the middle, surrounded by two separate sets of wires forming a cylindrical grid, a dielectric material outside of the grid, and finally a cylinder of metal conductor outside the dielectric, called the signal plate. The smaller capacity 256-bit system was constructed similarly, but built in a planar fashion rather than cylindrical,resulting in an even larger vacuum tube. The device used an indirectly heated cathode running up the middle, surrounded by two separate sets of wires and offered a storage cap acity of 4096 bits to 256 in the proposed production device. The Williams tube was an example of a general class of cathode ray tube (CRT) devices known as storage tubes. The primary function of a conventional CRT is to display an image by lighting phosphor using a beam of electrons fired at it from an electron gun at the back of the tube. Like the Williams Kilburn tube, the Selectron was also a random access storage device. Because of the popularity of magnetic core memory at the time, the Selectron tube was never put into mass production.1.2.1.5 Magnetic-core MemoryFigure 6 Magnetic-core MemorySecond major milestone in modern computer memory technology was magnetic core memory which was widely adopted. Core memory or magnetic core memory became a widespread form of random-access memory, relying on an array of magnetized rings and was invented in 1947 and developed up until the mid-1970s. It is said to be non-volatile and will not lose its contents when the power is removed. The te rm core comes from conventional transformers whose windings surround a magnetic core. The basic principle of core memory was using a core as a ring of ferrite that could be magnetized in one of two directions. As a result, the memory was able to store digital information either a 1 or 0. In core memory the wires twirl once through any given core, they are single turn devices. The core can take two states, encoding one bit, which can be read when selected by a sense wire. When the core is read, it is reset to a zero which is known as destructive readout. Circuits in the computer memory system then restore the information in an immediate re-write cycle. Magnetic core memory was initially very expensive to fabricate but prices dropped as the market developed. It was the standard form of memory system until displaced by solid-state memory in integrated circuits, starting in the early 1970s.1.2.1.6 Random access MemoryFigure 7 Random access MemoryRandom-access memory (RAM) is a form of computer data storage. A random-access device allows stored data to be accessed directly in any random order. Today, random-access memory takes the form of integrated circuits which is a set of electronic circuits on one small plate or chip of semiconductor material, normally silicon. One distinguishing characteristic of RAM is that it is possible both to read data from the memory and to write new data into the memory easily and rapidly. Both the reading and writing are accomplished the use of electrical signals. The other distinguishing characteristic of RAM is that it is volatile. A RAM must be provided with a constant power supply. If the power is interrupted, then the data are lost. Thus, RAM can be used only as temporary storage.The three main forms of modern RAM are static RAM (SRAM), dynamic RAM (DRAM) and phase-change memory (PRAM). In SRAM, a bit of data is stored using the state of a flip-flop. This form of RAM is more expensive to produce but is generally faster and req uires less power than DRAM. In modern computers, it is often used as cache memory for the CPU.DRAM stores a bit of data using a transistor and capacitor pair which together comprise a memory cell. The capacitor holds a high or low (0 or 1) charge and the transistor acts as a switch that lets the control circuitry on the chip read the capacitors state of charge or change it.Phase-change memory is also known as PRAM, is a type of non-volatile random-access memory. PRAM can offer much higher performance in applications where writing quickly is important, both because the memory element can be switched more quickly and also because single bits may be changed to either 1 or 0 without needing to first erase an entire block of cells. PRAMs high performance, thousands of times faster than conventional hard drives, makes it particularly arouse in nonvolatile memory roles that are currently performance-limited by memory access timing.ECC memory, which can be either SRAM or DRAM, includes spe cial circuitry to watch or correct random faults or memory errors in the stored data, using parity bits or error correction code. A parity bit or check bit is a bit added to the end of a string of binary code that indicates whether the number of bits in the string with the value one is even or odd. Parity bits are used as the simplest form of error detecting code. In information theory and coding theory with applications in computer science and telecommunication, error detection and correction or error control are techniques that enable reliable delivery of digital data over undependable communication channels.Many computer systems have a memory hierarchy consisting of CPU registers, on-die SRAM caches, external caches, DRAM, paging systems and virtual memory or swap space on a hard drive. This entire pool of memory may be referred to as RAM by many developers.1.2.1.7 Read Only MemoryFigure 8 Read Only MemoryRead-only memory (ROM) is a class of storage medium used in computers. Da ta stored in ROM cannot be modified, or can be modified only slowly or with difficulty. It is really only suitable for storing data which is not expected to need modification for the life of the device.When only a small number of ROMs with particular memory content is needed, a less expensive alternative is the programmable ROM (PROM). Like the ROM, the PROM is nonvolatile and may be written into only once. For the PROM, the writing process is performed electrically and may be performed by a supplier or customer at a time later than the original chip fabrication. Special equipment is required for the writing or programming process.Another variation on read only memory is the read mostly memory, which is useful for applications in which read operations far more frequent than write operation but for which nonvolatile storage is required. There are three common forms of read mostly memory, they are EPROM, EEPROM and flash memory.The optically erasable programmable read only memory (EPR OM) is read and written electrically, as with PROM. However, before a write operation, all the storage cells must be erased to the same initial state by exposure of the packaged chip to ultraviolet radiation. Erasure is performed by shining an intense ultraviolet light through a window that is designed into the memory chip. This expunction process can be performed repeatedly. It has the advantage of the multiple update capability.A more attractive form of read mostly memory is electrically erasable programmable read only memory (EEPROM). This is a read mostly memory that can be written into at any time without erasing prior contents, only the byte or bytes addressed are update. The write operation takes considerably longer than the read operation, on the other of several hundred microseconds per byte. The EEPROM combines the advantage of nonvolatility with the flexibility of being updatable in place, using ordinary bus control, address, and data lines. It is suppor