Currently, the problem of the benefits of long-term storage of information on various media and using new technologies is becoming increasingly relevant. It cannot be denied that the introduction of new technologies is associated with additional costs - replacing outdated systems is expensive. We will try, using traditional methods, to compare the costs of storing and using information for a long time (75 years) on various media: paper, disks, tape, film.
Currently, the problem of the benefits of long-term storage of information on various media and using new technologies is becoming increasingly relevant. It cannot be denied that the introduction of new technologies is associated with additional costs - replacing outdated systems is expensive. Using traditional methods, we compare the costs of storing and using information for a long time (75 years) on various media: paper, disks, tape and film.
The results of the analysis are framework, preliminary. To more accurately determine the cost of various options, a deeper, multi-year study similar to that conducted by ClipperGroup, Inc. in 2008
When calculating the cost taken into account:
- Remuneration and training / retraining of personnel employed at all stages of storage, accounting and use of information.
- Material costs associated with the acquisition and maintenance of fixed assets (racks, disk (hereinafter referred to as RAID) and tape (hereinafter referred to as streamer) drives, scanners, computers, microfilm equipment, etc.), consumables (paper, disks , tapes, films, etc.
- The costs of maintaining or renting premises, buildings, structures, providing ventilation, security and fire safety. A particularly important role is played by the costs associated with energy consumption.
- Software (subject to update).
Overhead costs are assumed to be the same for storage on paper and film and large for storage on disk and tape drives.
According to our estimates, long-term (for 75 years) storage, accounting and use of 1 conventional storage unit on paper (100 sheets) at present, at the existing level of remuneration, tariffs for electricity, etc., per year it costs on average 30 rub. Of these, about 23 rubles are spent on ensuring storage, about 5 rubles on accounting and use.
Part of the costs are one-time (for materials and payment for binding, paperwork, encryption, numbering of sheets, description, preparation of accounting documents, etc.), part - repeated after a certain number of years. For example, along with one-time cartoning works, periodic re-cartoning is practiced, associated with the purchase of new archive boxes, wages for employees. And this, in turn, entails the work of moving, labeling, etc. A fairly large share in the cost of storing “paper” cases is the issuance and lining of cases and often carried out dust removal. Depending on the state of the NSA, time-consuming, which means “expensive,” is the search for the necessary data.
Since all the main costs that form the cost of “paper business” are constantly growing (salary, rent and maintenance costs, materials, etc.), its storage is becoming more and more expensive every year. If in the first year the cost is 1 srvc. units hr amounts to 11.9 rubles, then at the end of the storage period (even at constant prices and salaries) - 49 rubles, i.e. 4 times more expensive.
Opportunities to reduce the cost of storage on paper are limited. They are real only with the involvement of modern technologies, the introduction of electronic search engines, electronic accounting, etc., which transforms the very traditional system of storage, accounting and use of documents on "paper" media.
The search for ways to reduce the cost of storing “paper” files can lead to the use of lower quality materials, savings on providing storage conditions, and, as a result, to the loss of documents.
The opposite picture is provided by the storage of data on film (microfilms, microfiche). The initial stage - the microfilming process, ensuring storage conditions - require serious material costs. One-time costs for microfilming 1 srvc. units hr amount to more than 800 rubles. They include the purchase of expensive equipment, staff training, the installation of a water treatment system, etc. Equipment is also necessary for quality control, reading information from the film. A significant share in the cost of production is the cost of the purchase of film, reagents, cleaners, waste disposal.
However, over time, the storage of 1 srvc. units hr it becomes cheaper on film, and then stabilizes at the same level, and will change little in the future.
As for the accounting and use of microfilms and microfiche, then (with the exception of the need for special rather expensive reading devices) there are not many differences from the “paper” version. It all depends on the features of the NSA.
As a result, according to our estimates, average cost of storage, accounting and use 1 srvc units hr on film (stored for 75 years) is about 40 rubles. But the film is stored much longer (in comparison with paper, and with disks, and with tape), and the relatively high cost is offset by the high safety and compactness of storage. In addition, modern technology allows marking films with barcodes and tags for subsequent machine processing and automation of data retrieval, as well as simultaneous digitization of data.
The ratio of the costs of storage, accounting and use is close to the “paper” option: from 40 rubles. about 30 rubles are spent on storage, about 6 rubles on accounting and use.
In 2008, ClipperNotes published the results of calculations comparing streamers (tape drives) and disk arrays. According to their findings, the tape drive has significant advantages over a RAID array in terms of cost and power consumption during long-term storage and large amounts of stored data.
The cost of storing on disks is almost 23 times higher than on tape, and the cost of energy when storing on disks is almost 290 times higher than on tape. So, for example, to keep the archive of 6.6 petabytes in size for constant access for 5 years , the cost of a disk system (RAID arrays, controllers, splitters, disks, power, cooling, etc.) will amount to $ 14.7 million (including the cost of electricity - $ 550 thousand), while the cost of a tape library is less than 700 thousand dollars (including the cost of electricity - 304 dollars). Based on these calculations, storage of 1 conditional storage unit within 1 year in a RAID array costs 5, 35 rubles; in the streamer - 2.5 rubles.
Costs are not evenly distributed over time. Most of them in both cases occur at the initial stage of storage, when all the necessary equipment is purchased. Then there is a reduction in costs per 1 unit. hr information.
Our calculations showed that the storage, accounting and use of 1 srvc. units hr (400 MB) on disks for 75 years on average per year will cost at 25 rubles. ClipperNotes conclusions are confirmed that the bulk of the costs are at the initial stage of storage and use. In contrast to storing information on paper and film, a significant share in the cost price is software. The share of equipment costs in accounting and use is increasing, since when storing information on tape or disk drives other, traditional methods of accounting are no longer possible. At the same time, a significant reduction may occur, and as a result, a reduction in staff costs.
The problems that are associated in electronic form are well known: possible incompatibility with new devices or new software; fragility of media (disks), which means the need for rewriting; viruses, etc.
In order to ensure greater safety and the most convenient and quick access to information, nowadays, combined storage methods are increasingly being used. For example, COM-systems allow you to transfer any digital data formats to microfilm. On the other hand, the practice of converting data from film to digital. The appearance of such devices (systems) indicates that the most effective (in terms of safety and cost) will be the combination of data storage in disk or tape drives and on tape.
T.I. Lyubina,
director of the State Archives State Archives
historical and political documents
Moscow region"
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Home\u003e Abstract\u003e Computer Science
Introduction 2
CHAPTER I. MEMORY OF THE COMPUTER. EXTERNAL MEMORY DEVICES 3
1.1 Computer memory and its types 3
1.2. External computer memory 4
1.2.1. Magnetic disk drives 6
1.2.2. . Hard drives (hard drives) 8
1.2.3. Floppy Disk Drive 11
1.2.4. CD-ROM 14
1.2.6. Flash memory 18
1.2.7. Holographic devices 19
1.2.8. MODS wheels 19
CHAPTER II. HISTORY AND PROSPECTS OF DEVELOPMENT OF INFORMATION STORAGE DEVICES 20
2.1. The history of the development of information storage devices 20
2.2. Prospects for the development of information storage devices 26
Conclusion 30
References 32
Appendix 1 33
Introduction
All personal computers use three types of memory: operational, permanent and external (various drives). Memory is needed both for source data and for storing results. It is necessary to interact with the peripherals of the computer and even to maintain the image visible on the screen. All computer memory is divided into internal and external. In computer systems, working with memory is based on very simple concepts. In principle, all that is required of computer memory is to store one bit of information so that it can later be retrieved from there.
Storage devices can be classified by the following criteria:
by type of storage elements
for functional purpose
by type of organization of circulation
by nature of reading
by storage method
by organization
The Object of the course work is a modern information storage device.
The purpose of the study is to study the history and development prospects of information storage devices in the modern world.
consider the concept of memory, its types;
consider the concept of information storage devices, their types, principles of recording, storage, reading, basic user characteristics;
to study the history and future prospects of the development of information storage devices.
CHAPTER I. MEMORY OF THE COMPUTER. EXTERNAL MEMORY DEVICES
1.1 Computer memory and its types
Computer memory is a set of devices for storing programs, input information, intermediate results and output data. The classification of memory is presented in Appendix 1. Memory is divided into the following types 1:
Internal memory is designed to store relatively small amounts of information when it is processed by a microprocessor. External memory is designed for long-term storage of large amounts of information regardless of whether the computer is turned on or off.
Non-volatile memory is called that is erased when you turn off the computer. Non-volatile memory is called memory, which is not erased when you turn off the computer.
Non-volatile internal memory includes read-only memory (ROM). The contents of the ROM are installed at the factory and do not change. Programs that provide a basic set of computer device control functions are written to the ROM.
Volatile internal memory includes random access memory (RAM), video memory, and cache memory. RAM provides the modes of recording, reading and storage of information, and at any time you can access any randomly selected memory location. Part of the RAM is reserved for storing images (video memory). High-speed cache is used to increase the speed of computer operations and is used when exchanging data between the microprocessor and RAM.
External memory can be random access and sequential access. Random access memory devices allow access to an arbitrary data block in about the same access time.
1.2. External computer memory
According to the type of access to information, external memory devices are divided into: direct (random) access devices and sequential access devices. With direct access, the access time to the information does not depend on its location on the medium. With sequential access - depends on the location of the information.
VZU are used for storing large amounts of information - data sets, user programs and operating systems. In the process of operation of the computing system, as necessary, an operational exchange of information arrays between the VZU and the main memory.
To work with external memory, you must have a drive (a device that provides recording and (or) reading information) and a storage device - media.
The main types of drives 2:
floppy disk drives (HMD);
drives on hard magnetic disks (HDD);
magnetic tape drives (NML);
cD-ROM, CD-RW, DVD drives.
They correspond to the main types of media:
flexible magnetic disks (Floppy Disk) (with a diameter of 3.5 ’’ and a capacity of 1.44 MB), removable media drives;
hard magnetic disks (Hard Disk);
cartridges for streamers and other NML;
cD-ROM, CD-R, CD-RW, DVD.
Storage devices are usually divided into types and categories in connection with their principles of operation, operational and technical, physical, software and other characteristics. So, for example, according to the operating principles, the following types of devices are distinguished: electronic, magnetic, optical and mixed - magneto-optical. Each type of device is organized on the basis of appropriate technology for storing / reproducing / recording digital information. Therefore, in connection with the type and technical design of the storage medium, there are: electronic, disk and tape devices.
The main characteristics of drives and media 3:
information capacity;
information exchange speed;
reliability of information storage.
Let us dwell in more detail on the consideration of the above drives and carriers.
1.2.1. Magnetic disk drives
The principle of operation of magnetic storage devices is based on methods for storing information using the magnetic properties of materials. As a rule, magnetic storage devices consist of actual devices for reading / writing information and a magnetic medium onto which, directly, recording is made and from which information is read. Magnetic storage devices are usually divided into types in connection with the performance, physical and technical characteristics of the storage medium, etc. Most often distinguished: disk and tape devices. The general technology of magnetic storage devices consists in magnetizing, by an alternating magnetic field, portions of a medium and reading out information encoded as regions of variable magnetization. Disk media, as a rule, are magnetized along concentric fields - tracks located along the entire plane of a discoid rotating medium. Recording is made in digital code. Magnetization is achieved by creating an alternating magnetic field using read / write heads. The heads are two or more magnetic controlled circuits with cores, the windings of which are supplied with alternating voltage. A change in the polarity of the voltage causes a change in the direction of the lines of magnetic induction of the magnetic field and, upon magnetization of the carrier, means a change in the value of the information bit from 1 to 0 or from 0 to 1.
Disk devices are divided into flexible (Floppy Disk) and hard (Hard Disk) drives and media. The main property of disk magnetic devices is the recording of information on a medium onto concentric closed tracks using physical and logical digital coding of information. Flat disk media rotates during reading / writing, which ensures the maintenance of the entire concentric track, reading and writing is carried out using magnetic read / write heads, which are positioned along the radius of the medium from one track to another. Disk devices typically use a recording method called the Non Return Zero (NRZ) method. Recording by the NRZ method is carried out by changing the direction of the magnetization current in the windings of the read / write heads, causing a reverse change in the polarity of the magnetization of the cores of the magnetic heads and, accordingly, alternating magnetization of the carrier sections along concentric tracks over time and moving around the circumference of the carrier. In this case, it does not matter whether the magnetic flux changes from a positive direction to a negative or vice versa, only the fact of a polarity reversal is important.
To record information, as a rule, various methods of encoding information are used, but all of them suggest using not the direction of the magnetic induction lines of the elementary magnetized point of the carrier as an information source, but a change in the direction of induction in the process of moving along the carrier along a concentric track over time. This principle requires tight synchronization of the bit stream, which is achieved by encoding methods. Data encoding methods do not affect changes in the direction of the stream, but only specify the sequence of their distribution over time (the method of synchronizing the data stream), so that, when reading, this sequence can be converted to the original data 4.
1.2.2. . Hard drives (hard drives)
Hard disk drives combine media (media) and a reader / writer in one housing, as well as, often, the interface part, called the controller itself hard drive. A typical design of a hard disk is the execution in the form of a single device - a camera, inside of which there is one or more disk carriers mounted on one spindle and a block of read / write heads with their common drive mechanism. Usually, near the camera of carriers and heads are located control circuits for heads, disks and, often, the interface part and / or controller. On the device’s interface card, the actual interface of the disk device is located, and the controller with its interface is located on the device itself. Drive circuits are connected to the interface adapter using a set of loops.
Information is recorded on concentric tracks evenly distributed throughout the media. In the case of more than one disk, the number of media all tracks located one below the other are called a cylinder. Read / write operations are performed in a row over all cylinder tracks, after which the heads are moved to a new position.
A sealed chamber protects carriers not only from the penetration of mechanical dust particles, but also from exposure to electromagnetic fields. It should be noted that the camera is not completely tight because It is connected to the surrounding atmosphere using a special filter that equalizes the pressure inside and outside the chamber. However, the air inside the chamber is as dust-free as possible. the smallest particles can lead to damage to the magnetic coating of disks and loss of data and device performance.
Disks rotate constantly, and the rotation speed of the media is quite high (from 4,500 to 10,000 rpm), which provides high read / write speeds. According to the size of the carrier diameter, 5.25, 3.14, 2.3 inch disks are most often produced. The diameter of the media of non-removable hard disks does not impose any restrictions on the compatibility and portability of the media, with the exception of the form factors of the PC case, therefore, manufacturers choose it according to their own reasons.
Currently, for positioning read / write heads, most often, step and linear motors of positioning mechanisms and head movement mechanisms in general are used.
In systems with a stepper mechanism and an engine, the heads move by a certain amount corresponding to the distance between the tracks. The discreteness of steps depends either on the characteristics of the stepper motor, or is set by servo marks on the disk, which may be of a magnetic or optical nature. An additional servo head is used to read magnetic marks, and special optical sensors are used to read optical tags.
In systems with a linear drive, the heads are moved by an electromagnet, and special service signals recorded on the carrier during its production and read out when positioning the heads are used to determine the required position. Many servo devices use an entire surface and a special head or optical sensor. This method of organizing servo data is called a dedicated record of servo signals. If servo signals are recorded on the same tracks as data and a special servo sector is allocated for them, and reading is performed by the same heads as data reading, then this mechanism is called built-in recording of servo signals. Dedicated recording provides faster performance, and built-in - increases the capacity of the device.
Linear drives move the heads much faster than step drives, in addition, they allow small radial movements “inside” the track, making it possible to track the center of the circumference of the servo track. This ensures that the head position is best for reading from each track, which significantly increases the reliability of the data being read and eliminates the need for time-consuming correction procedures. As a rule, all devices with a linear drive have an automatic mechanism for parking the read / write heads when the device is turned off.
Head parking is the process of moving them to a safe position. This is the so-called “parking” position of the heads in the area of \u200b\u200bthe discs where the heads rest. There, as a rule, no information is recorded except for servo data; this is a special “Landing Zone”. To fix the drive of the heads in this position, most railways use a small permanent magnet when the heads take a parking position - this magnet contacts the base of the housing and keeps the position of the heads from unnecessary vibrations. When the drive starts, the linear motor control circuit “tears” the latch, supplying an amplified current pulse to the motor, positioning heads. A number of drives also use other methods of fixation - based, for example, on the air flow created by the rotation of the disks. In a parked state, the drive can be transported under rather poor physical conditions (vibration, shock, shock), as there is no danger of damage to the surface of the carrier by the heads. Currently, on all modern devices, drive heads are parked automatically by the internal circuits of the controller when the power is turned off and does not require any additional software operations, as was the case with the first models.
During operation, all mechanical parts of the drive are subject to thermal expansion, and the distance between the tracks, the spindle axes and the positioner of the read / write heads changes. In the general case, this does not affect the drive operation in any way, since feedback is used for stabilization, however, some models occasionally recalibrate the head drive, accompanied by a characteristic sound that resembles the sound at the initial start, adjusting the system to changed distances.
The electronics board of a modern hard disk drive is an independent microcomputer with its own processor, memory, input / output devices and other traditional attributes inherent in a computer. The board may have many switches and jumpers, but not all of them are intended for use by the user. As a rule, user guides describe the purpose of only jumpers associated with the choice of the logical address of the device and its operating mode, and for drives with SCSI interface - jumpers responsible for controlling the resistor assembly (stabilizing load in the circuit) 5.
1.2.3. Floppy disk drive
The main internal elements of the drive are a diskette frame, a spindle motor, a drive head unit and an electronics board.
The spindle motor is a flat multi-pole motor with a constant rotation speed of 300 rpm. The head block drive motor is a stepper, with a worm, gear or belt drive.
To identify the properties of a floppy disk, three mechanical pressure sensors are installed on the electronics board near the front end of the drive: two under the protection and recording density holes, and a third behind the density sensor to determine when the floppy is lowering. A floppy disk inserted into the slot gets inside the floppy disk, where the protective shutter slides from it, and the frame itself is removed from the stopper and lowered down - the metal ring of the diskette rests on the spindle motor shaft, and the lower surface of the diskette on the lower head (side 0 ) At the same time, the upper head is released, which, under the action of a spring, is pressed against the upper side of the diskette. On most drives, the speed of lowering the frame is not limited in any way, which is why the heads inflict a noticeable blow on the surfaces of the floppy disk, and this greatly reduces the period of their reliable operation. Some drive models (Teac, Panasonic, ALPS) have a micro-lift moderator for smooth lowering of the frame. To extend the life of diskettes and heads in drives without a micro-lift, it is recommended that you hold the drive button with your finger when inserting a diskette, preventing the frame from dropping too sharply. On the shaft of the spindle motor there is a ring with a magnetic lock, which at the beginning of rotation of the engine tightly captures the diskette ring, while centering it on the shaft. In most drive models, the signal from the floppy down sensor causes a short-term engine start to capture and center it.
The drive is connected to the controller using a 34-wire cable, in which even wires are signal, and odd wires are common. The general interface option provides for connecting up to four drives to the controller, and up to two for the IBM PC. In general, the drives are connected completely parallel to each other, and the drive number (0..3) is set by jumpers on the electronics board; in the version for IBM PC, both drives are number 1, but are connected using a cable in which the selection signals (wires 10-16) are inverted between the connectors of the two drives. Sometimes, pin 6 is removed from the drive connector, playing in this case the role of a mechanical key. The drive interface is quite simple and includes signals for selecting a device (four devices in the general case, two for the IBM PC version), starting the engine, moving the heads one step of writing, read / write data, as well as information signals from the drive - the beginning of the track , a sign of installing the heads on the zero (external) track, signals from sensors, etc. All work on coding information, searching for tracks and sectors, synchronization, error correction is performed by the controller.
A floppy disk or floppy disk is a compact low-speed low-capacity medium for storing and transferring information. There are two sizes of floppy disks: 3.5 ”, 5.25”, 8 ”(the last two types are obsolete).
Structurally, the floppy disk is a magnetic disk floppy disk enclosed in a case. The floppy disk has a hole for the drive spire, a hole in the case for accessing the read / write heads (closed with an iron shutter in 3.5 ”), a cut-out or a write protection hole. In addition to floppy disk 3.5 ”- high-density floppy disk - a hole of the specified density (high / low). The 3.5 diskette is write-protected if the protection hole is open.
The following notation is used for floppy disks:
SS single side - single-sided disk (one working surface).
DS double side - double-sided disk.
SD single density - single density.
DD double density - double density.
HD high density
A floppy drive is fundamentally similar to a hard drives. The rotation speed of the floppy disk is about 10 times slower, and the heads touch the surface of the disk. Basically, the information structure on a floppy disk, both physical and logical, is the same as on a hard disk. From point of view logical structure there is no partition table 6 on the diskette.
1.2.4. CD-ROM
The most common representative of optical technology is a CD-ROM, which is characterized by:
Greater reliability than a hard drive
Large capacity, about 700 MB
CD-ROM practically does not wear out
The minimum data transfer speed of the CD-ROM is 150 Kb / s and increases depending on the model of the drive, i.e. 52-speed CD-ROM, will have 52 * 150 \u003d 7.8 Mb / s.
A typical drive consists of an electronics board, a spindle motor, an optical read head system, and a disk loading system. The electronics board contains all drive control circuits, an interface with a computer controller, interface connectors and an audio output.
The spindle motor is used to bring the disk into rotation with constant or variable linear speed. Maintaining a constant linear velocity requires a change in the angular velocity of the disk depending on the position of the optical head. When searching for fragments, a disk can rotate at a higher speed than when reading, therefore a good dynamic characteristic is required from a spindle motor; the engine is used both for acceleration and for braking the disk.
A stand is fixed on the axis of the spindle motor, to which the disk is pressed after loading. The surface of the stand is usually coated with rubber or soft plastic to prevent slipping of the disc. The disk is clamped to the stand using a washer located on the other side of the disk; the stand and the washer contain permanent magnets, a force whose attraction presses the washer through the disk to the stand.
The optical head system consists of the head itself and its movement system. The head contains a laser emitter based on an infrared laser LED, a focusing system, a photodetector and a preamplifier. The focusing system is a movable lens, driven by a voice coil electromagnetic system (voice coil), made by analogy with a moving loudspeaker system. A change in the magnetic field strength causes the lens to move and the laser beam to refocus.
The disk loading system is carried out in two versions: using a special case for the disk (caddy) inserted into the receiving hole of the drive, and using a sliding tray (tray), on which the disk is placed.
A standard disk consists of three layers: a polycarbonate substrate on which the disk relief is stamped, a reflective coating of aluminum, gold, silver or another alloy soaked on it, and a thinner protective layer of polycarbonate or varnish, on which inscriptions and drawings are applied. The informational relief of the disk consists of a spiral path going from the center to the periphery, along which recesses (pits) are located. Information is encoded by alternating pits and the gaps between them.
Reading of information from the disk occurs due to registration of changes in the intensity of the radiation of a low-power laser reflected from the aluminum layer. The receiver or photosensor determines whether the beam reflected from a smooth surface, whether it was scattered or absorbed. The scattering or absorption of the beam occurs in places where recesses (strokes) were applied during the recording process. Strong reflection of the beam occurs where these depressions are absent. A photosensor located in a CD-ROM drive senses a scattered beam reflected from the surface of the disc. Then this information in the form of electrical signals is fed to the microprocessor, which converts these signals into binary data or sound.
The depth of each stroke on the disk is 0.12 μm, the width is 0.6 μm. They are located along a spiral path, the distance between adjacent turns of which is 1.6 μm, which corresponds to a density of 16,000 turns per inch or 625 turns per millimeter. The length of the strokes along the recording track can range from 0.9 to 3.3 microns. The track starts at a distance from the center hole and ends about 5 mm from the outer edge.
If it is necessary to find a place for recording certain data on a CD, then its coordinates are preliminarily read from the table of contents of the disk, after which the reader moves to the desired turn of the spiral and waits for a certain sequence of bits to appear.
Each disk block recorded in CD - DA (audio compact disc) format contains 2352 bytes. On the CD-ROM, 304 of them are used for synchronization, identification and correction of error codes, and the remaining 2048 bytes are used to store useful information. Since 75 blocks are read per second, the speed of reading data from CD-ROM discs is 153,600 bytes / s (single-speed CD-ROM), which equals 150 Kb / s. Since the maximum volume of data that can be read for 74 minutes and 75 blocks for 2048 bytes is read per second, it is easy to calculate that the maximum capacity of a CD - ROM will be 681,984,000 bytes (about 650 MB).
The algorithm of the CD-ROM drive.
A semiconductor laser generates a low-power infrared beam that hits a reflective mirror.
The servomotor, on the instructions of the built-in microprocessor, shifts the movable carriage with a reflecting mirror to the desired track on the CD.
The beam reflected from the disk is focused by a lens located under the disk, is reflected from the mirror and enters the separation prism.
The separation prism directs the reflected beam to another focusing lens.
This lens directs the reflected beam to the photosensor, which converts light energy into electrical pulses.
The signals from the photosensor are decoded by the built-in microprocessor and transmitted to the computer in the form of data.
Since every bit is important for program and data files, CD-ROM drives use highly sophisticated error detection and correction algorithms. Thanks to such algorithms, the probability of incorrect data reading is less than 0.125.
To implement these error correction methods, 288 control bytes are added to every 2048 useful bytes. This allows you to recover even severely damaged data sequences (up to 1000 error bits in length). The use of such sophisticated methods for detecting and correcting errors is associated, firstly, with the fact that compact discs are very susceptible to external influences, and, secondly, because such media were originally developed only for recording audio signals, the accuracy requirements of which are not so high 7.
1.2.5. DVD
Further development in the field of optical recording led to the advent of the DVD standard. A CD of this format has the same dimensions (4.75 ”) as a CD, but has a large capacity. In order to achieve a six-fold increase in data storage density compared to CD-R (RW), two key characteristics of recording devices had to be changed: the wavelength of the recording laser and the relative aperture of the lens that focuses it. CD-R technology uses an infrared laser with a wavelength of 780 nanometers (nm), while DVD-R (RW) uses a red laser with a wavelength of either 635 or 650 nm. At the same time, the relative lens aperture of a typical CD-R (RW) device is 0.5, and the DVD-R (RW) device is 0.6. Such characteristics of the equipment can be applied to dVD-R discs(RW) tags are only 0.40 microns in size, which is much smaller than the minimum CD-R (RW) tags - 0.834 microns.
A DVD is a medium that can contain any type of information that is usually found on mass-produced DVDs: video, audio, images, data files, multimedia applications, and so on. Depending on the type of information recorded, DVD-R and DVD-RW can be used on standard DVD playback devices, including most DVD-ROM drives and DVD-Video players.
Features of some DVD formats.
1.2.6. Flash memory
With the advent of flash memory, electronics manufacturers were able to equip their devices with a new type of storage without any problems and costs. There were benefits - low power consumption, high reliability and resistance to external influences and loads.
USB Flash drive - a portable device for storing and transferring data from one computer to another. Compact, lightweight, convenient and surprisingly easy to operate. For its operation, neither connecting cables, nor power sources, nor additional software are needed. Features USB flash Drive: high speed USB data transfer, write protection with a switch on the case, password protection, no drivers and external power required, can be formatted as a boot disk, data storage up to 10 years.
In 1994, SanDisk introduced the first revision of the CompactFlash specification. The theoretical limit for the capacity of CompactFlash-based drives is 137 GB. Currently, models with capacities from 16 MB to 12 GB 8 are available on the market.
1.2.7. Holographic devices
Holographic recording allows recording up to 1.6 TB of data onto a standard-sized disc. The essence of know-how is quite simple. For recording, the laser beam is divided into reference and signal streams, the latter is processed using a spatial light modulator (Spatial Light Modulator - SLM). This device converts the data intended for storage, consisting of sequences 0 and 1, into a “chess field” of light and dark dots - each such field contains about a million bits of information.
After the intersection of the reference beam and the projection of the “checkerboard”, a hologram is formed, and the interference pattern is recorded on the carrier. By changing the angle of inclination of the reference beam, as well as its wavelength or carrier position, several different holograms can be recorded on the same area at the same time - this process is called multiplexing. To read the data, it is enough to illuminate the disk with the corresponding reference beam and “read” the resulting hologram section, in fact - the very “chessboard” - using the sensor. So the original bits of information are restored. In addition to storage volumes, other characteristics are also impressive in the technology. So, for example, the declared data transfer rate is 960 Mbit / s.
1.2.8. MODs
Physicists at Imperial College London have developed an optical disc the size of a CD or DVD, which houses 1 terabyte of data (472 hours of high-quality video). The new format is called MODS (Multiplexed Optical Data Storage). Its secret lies not only in the size of one pita or in their tight packaging. The main innovation is that one pit in MODS encodes not one bit (1 or 0, like all recording systems), but dozens of bits. The fact is that each pit in the new format is not symmetrical. It contains a small additional cavity, tilted in depth at one of 332 angles. They created equipment and special software that accurately identifies subtle differences in light reflection from such pits. According to the forecasts of physicists, serial MODS disks and drives for them can come to the market between 2010 and 2015, provided that the further work of the group is funded. Interestingly, these drives will be backward compatible with DVDs and CDs, although, of course, current MODS drives will not be able to read 9.
The main user characteristics of the considered types of VZU are given in Appendix 2.
CHAPTER II. HISTORY AND PROSPECTS OF DEVELOPMENT OF INFORMATION STORAGE DEVICES
2.1. The history of the development of information storage devices
A distant 1898 should be taken as a reference point in the development of magnetic memory. It was in that year that the Danish engineer W. Poulsen demonstrated a device that could record speech on a steel string. Poulsen moved from one end of the wire to the other, speaking into a microphone connected to an electromagnetic coil. When Poulsen returned the cart to its original position and replaced the microphone with a speaker, his voice was heard as the cart moved. The basis of modern devices for magnetic recording of information is the same principle with the only difference being that the string is replaced by a thin magnetic film. Currently used methods of recording and reading information can be divided into two groups: magnetic and optical.
Magnetic recording technology has become widely used in various memory elements since the early 1950s. It is this technology that is still used in most computers.
In modern media, one bit of magnetic information is one magnetic domain, the direction of the magnetization vector in which can be changed by an external field. In magnetic recording, the so-called longitudinal domains are used, the magnetization of which is oriented in the plane of the disk. The recording of one bit of information is carried out by supplying current to an electric coil. Reading information with this scheme of work can be carried out in various ways. This scheme is used in the process of working hard drives of computers, floppy disks and streamers. To record bits with a high recording density, it is necessary that not only the distance between the magnetic medium and the read / write head is small, but also that the medium itself should be as thin and smooth as possible.
One of the best-known magnetic materials used for recording is powder in a bonding matrix (e.g., varnish). The powder is a microparticle with a large remanent magnetization ranging in size from 0.05 to 1.0 μm, a Curie temperature from 125 to 770 K, and a coercive force I c from 22 to 240 kA / m (0.4-3 kOe) depending on the material . The compound Y-Fe, O 3 in the recent past was the most popular material for magnetic tape drives. Later it was shown that the solid solution of y-Fe-, O 3 and y-Fe 3 O 4 compounds, as well as cobalt-containing y-Fe, O 3 have a significantly greater coercive force than the y-Fe, O .. compound. N from significantly depends on the size and shape of the particles and, for example, in the case of barium ferrite N from can vary from 56 to 240 kA / m (700-3000 Oe).
Unlike powder materials, thin films are almost completely magnetic material, and therefore, in the process of recording information, all film material is in the zone of action of a large magnetic field. At the same time, during reading, the field created by individual domains is concentrated near the film surface (near the head) and, therefore, the information can be read more efficiently. Thus, the use of films makes it possible to achieve a higher recording density than powder materials. As materials for recording information, for example, films of cobalt alloys deposited on aluminum or glass plates are used. Moreover, their rotation speed can reach 7200 rpm. The thickness of the magnetic layer in film longitudinal media is about 10-50 nm. In recent years, disks with a recording density of several Gbps per cm 2 have been commercially available, that is, one bit of information has a size of 0.8 x 0.06 microns or less.
To prevent damage to the film, especially when the disk begins to move, texturing of the disks is carried out: crater-like cones with a height of about 20 nm are applied to the rotating disk by pulsed laser radiation. The cones are arranged in a spiral starting from the inner radius of the disc, the rest of the surface of the disc has minimal roughness, is working and is used for magnetic recording. It is expected that in the near future almost direct contact between the medium and the head will be achieved. For this purpose, it is necessary to use practically smooth materials with a thickness of 5-10 nm, coated with a layer of lubricant, which provides almost frictionless movement of the head relative to the disk plane.
The following requirements are also imposed on media for magnetic recording: stability of properties when temperature changes, mechanical stresses, radiation and dampness; unlimited number of recording cycles and the safety of recorded information for more than 30 years; the possibility of applying anti-friction / protective coatings and the use of substrates with good aerodynamics and, most importantly, low production costs.
The advantages of magnetic recording include the simplicity and high reliability of recording (low probability of error), higher write / read speed compared to optical systems; low cost of one bit and relatively low cost of further increase in recording density. The disadvantages of magnetic systems are the limitation of the recording speed by the inductance of the ring used, as well as a certain limitation of the disk capacity. When using mechanical systems, restrictions are also imposed on the time of access to information and the accuracy of head positioning.
At present, induction heads are used for magnetic recording of information. During the operation of the head, the field created by the electric microcoil is concentrated with the help of a magnesium-wire in the immediate vicinity of the surface of the disk. Unlike a disk, the head can only move in the radial direction. Longitudinal domains of various orientations are recorded by changing the direction of the current in the microcoil. There are universal heads that combine both the recording and playback functions. Modern hard drives with a capacity of 120 GB have six heads for recording and reading information.
The most dense magnetic recording was achieved using thin-film heads for reading information, the action of which is based on the effect of giant magnetoresistance. This effect is a change in the resistance of materials under the influence of a magnetic field. It was discovered by Lord Kelvin in 1856 in ordinary iron and amounted to 1/3000 of the value of iron resistance under normal conditions. Scientists were able to find substances in which the relative change in resistance exceeds 1% / Oe. This gigantic effect is used in the reading heads of computers to register the field created by one domain (the magnetic field on the surface of the disk does not exceed 20-25 Oe). Note that in modern computers, information is recorded using an induction head, and reading is performed using a shielded magnetoresistive head.
In the mid-1970s - early 1980s basic research in the field of optical recording has reached a level that allowed such industrial giants as RCA, Sony and Philips to launch optical storage devices. The first optical disc for storing information was released in 1985. The most famous devices of this kind in Russia are compact discs (CDs). A laser diode operating in the near infrared region of the spectrum is integrated into each of the systems for reading information from a CD. This diode is able to easily detect holes pitted on the surface of the disk with a characteristic size of about 1 μm and thereby read the recorded information. The increase in the recording density of information on optical disks is to some extent constrained by the absence of solid-state lasers with a shorter wavelength. Released CDs allow you to overwrite information up to a hundred times. Optical systems (the so-called Jukebox) of the highest capacity can record up to 1.45 Tbps on 278 discs.
The logical continuation of these works was the development of the magneto-optical method of recording information. In addition to the longitudinal recording discussed above, which is used to create magnetic memory, there is also a perpendicular recording in which the domain magnetization vector is oriented perpendicular to the disk plane. This type of recording is used in magneto-optical memory systems. The first commercial version of the magneto-optical system was not released until 1994.
Magnetooptical systems use the polar Kerr effect in their work. Information on the orientation of the magnetization of the domain is obtained by analyzing the degree of rotation of the plane of polarization of the laser beam when reflected from the film (about 0.3 °). The first such systems used ferrimagnetic amorphous alloys of rare-earth and transition metals with perpendicular magnetic anisotropy. The composition of the films is selected so that the temperature at which the domain reversal occurs occurs close to the point of magnetic compensation or the Curie point, where H c significantly reduced. Effective compositions for magnetooptical recording are considered GdFe, TbCo, TbFe, TbFeCo, Co / Pt, Co / Pd, etc.
Currently, there are, for example, 5.25-inch rewritable removable (portable) magneto-optical disks with a capacity of up to 2.3 GB, 14-inch double-sided disks have a capacity of 12 GB. It is expected that in the near future the figure will increase to 20 GB even for a 5.25-inch disk (for two-way recording).
For recording, it is necessary to fulfill a number of magnetic, thermomagnetic and magneto-optical requirements: the direction of the magnetic moment of the domain should be perpendicular to the plane of the film; the distribution of magnetization over the film must be resistant to the effects of demagnetizing fields and small temperature fluctuations; a regular and reproducible domain structure with a domain size of about 1 μm should exist in the material: the possibility of decreasing the coercive force in magnitude by about an order of magnitude when heated; the absence of changes in neighboring domains upon heating (relatively poor thermal conductivity); sufficient (for reading) magnitude of the polar Kerr effect: the maximum possible signal-to-noise ratio (more than 25 dB) in the entire operating temperature range, etc. 10
2.2. Prospects for the development of information storage devices
An important area of \u200b\u200bscientific research in this area is the study of effects that affect superdense recording of information, such as thermal limitations, the so-called magnetic temporal effects and fluctuations of a different nature. However, the problem is not only what medium to use for recording information, but also how to write and read this information from this medium. For example, if a laser beam is directly used to write and read information, then the size of one bit of information cannot be significantly less than half the wavelength. Digital video discs already use a red laser with λ ≈ 630-635 nm, the near future in this area is the widespread use of a blue semiconductor GaN laser with a wavelength of 410-415 nm.
Scientists are developing several optical methods for recording and storing information. The most famous of them is the so-called DVD-technology, which has partially replaced the usual CD. The use of DVD-media allows you to produce, for example, two-hour videos recorded on one disc.
The researchers’s attention is attracted by the near-field optical memory. Near-field optics uses the fact that light can pass through holes much smaller than the wavelength λ . However, the light can spread over a very short distance - the so-called near field region. Scientists propose implementing this scheme by, for example, perforating a hole with a diameter of about 250 nm at the metal-coated end of the laser diode. The recording technology itself consists in using an optical head flying at a low altitude from the substrate, containing a recording ring for magnetic recording and two optical elements. One of these elements is a solid immersion lens. The lens is used to focus the laser beam into an ultra-small spot that is then projected onto the surface of the disc. According to some estimates, reducing the hole size on the laser to 30 nm can make it possible to achieve a recording density of more than 80 Gbit / cm 2.
Devices are actively being developed that make it possible to record and read information in the volume of material, that is, to carry out three-dimensional storage of information. Using three-dimensional (3.0-memory) optical memory allows you to record up to 10 12 bits per 1 cm 3. The place of a bit in the volume of material can be determined using simple spatial, spectral, or temporal coordinates. So, for example, in a holographic recording, the concept of which arose in the 1960s, information is stored in the interior as “pages” of electronic images.
If the DVDs we mentioned above have only two layers of information recording on each side, then the two-photon recording technology being developed now allows you to use several hundred layers on each side of the disk (the prototypes created have 100 layers with a thickness of 8 mm). With this recording method, an atom or molecule can transfer from one energy state to another only when two photons are simultaneously absorbed. The use of two laser beams makes it easy to vary the location of the information bit in the thickness of the material. The induced changes in this case can be recorded as changes in the absorption, fluorescence, reflectivity or electrical properties of the material at the location of the bit. This technology will allow you to save up to 100 GB of information on one disk of the same size as CD and DVD. One promising medium that can, for example, absorb or fluoresce when recording bits is spirobenzopyran. However, at room temperature, the information recorded in it can be stored for no more than 20 hours. For an unlimited time, this material can only store information at a temperature of -32 ° C, that is, at dry ice temperature. The possibility of using bacteriorhodopsin and nitronaphthialdehyde (rhodamine B) for two-photon recording of a photochromic protein is also being investigated.
Research is also being conducted on new possibilities for three-dimensional recording of information, which makes it, in a sense, four-dimensional. In addition to the usual method of recording, it is also proposed to use such information about each recording point as a wavelength, time or molecular structure (for example, to record information at the same point in space at different wavelengths). Thus, it will be possible to record up to 100 bits of information at one point in micron-sized space.
However, purely optical recording methods, in which the recording medium is located at a noticeable distance from the laser, have one important limitation - the minimum bit size of the recorded information is limited to λ /2. This is due to diffraction restrictions. Even when using a blue solid-state laser, the linear size of one bit of information can only be about 215 nm. Although there are no fundamental restrictions on the creation of solid-state lasers with a wavelength of less than 400 nm, the difficulties in creating well-controlled compact lasers increase markedly with a further decrease in the wavelength. Thus, it should be expected that even with the full development of three-dimensional memory and using a blue laser, purely optical methods will allow recording no more than 10 "4-10 15 bits of information in one cubic centimeter. To achieve a recording density of 10" 4 / cm in computers 3 will need at least 15-20 years.
At present, other types of optical memory are being developed that use, for example, individual molecules as information carriers or offer to switch to multi-level logic instead of the generally accepted binary one.
The use of thermomechanical processes for reading and writing information on thin polymer organic films also seems promising. IBM scientists are proposing to use the so-called millipede for this - thousands of cantilevers (sensitive elements) mounted on a single silicon wafer, and each of the cantilevers can write and read information to / from the polymer medium.
However, unlike the development of magnetic memory technology, bringing these works to an industrial prototype requires huge financial costs. At the same time, studies of the magnetic recording method carried out to date now already allow recording densities to be doubled in one year. Further development of magnetic memory does not require excessively high costs. The price of one megabyte of magnetic information has now decreased by about 500 times from its initial price and does not exceed several tenths of a cent. Thus, it can be assumed that in the next 7-10 years, magnetic materials will remain the most used medium for recording information (at least for computer hard drives) and in the near future will successfully compete with purely optical and other methods 11.
Conclusion
To summarize the results of the course work.
External memory is designed for long-term storage of programs and data. Devices external memory (drives) are non-volatile, turning off the power does not result in data loss. They can be built into the system unit or made in the form of independent units connected with the system through its ports. An important characteristic of external memory is its size. The amount of external memory can be increased by adding new drives. No less important characteristics of external memory are the time of access to information and the speed of information exchange. These parameters depend on the device for reading information and the organization type of access to it.
The speed of information exchange depends on the speed of its reading or writing to the medium, which is determined, in turn, by the speed of rotation or movement of this medium in the device.
External memory devices are, first of all, magnetic devices for storing information. By the method of writing and reading, drives are divided, depending on the type of media, into magnetic, optical and magneto-optical.
Previously, in computing, external devices (VZU) were classified as discrete information storage devices, mainly on magnetic tapes, drums, and disks.
Very soon, a novelty will appear on the market for information storage devices - it will be a device for accumulating information on special disks like CDs. They will support the DVD standard and have a capacity of 4.72 GB, and on them it will be possible to record information and naturally read more than once. This development will revolutionize the theory of storage and storage of information. This time is very close.
Scientifically based forecasts state that the improvement of electronic equipment and the use of new highly efficient storage media in combination with the widespread use of bionics methods in solving problems associated with the synthesis of storage devices will allow the creation of storage devices that are close in terms of human memory.
List of references
Allanakh I.N. External storage devices. M, 1991.
Batygov M., Denisov O. Hard disk drives. M., 2001.
Gilyarovsky R.S. Fundamentals of computer science. - M.: Exam, 2003.
Hook. M. Hardware IBM PC. Encyclopedia. - St. Petersburg: Peter, 2001.
Izvozchikov V.A. Computer science in concepts and terms. - M .: Education, 1997.
Informatics / Ed. N.V. Makarova. M., 2002.
Kozyrev A.A. Computer science. - M.: Mikhailov Publishing House, 2003.
Lebedev O. N. Memory microcircuits and their application. M., 1990.
Leontiev V.P. The latest PC encyclopedia. - M.: Prospect, 2003.
Fundamentals of modern technology / Ed. Khomanenko A.D. Hoffmann V.E. Maltseva P.B. M., 1998.
Ostreykovsky V.A. Computer science. - M.: Higher School, 2005.
Modern information technologies and networks. Unit 2. - M .: Modern Humanitarian University, 2001.
Ugrinovich N. Computer Science and information Technology. - M .: BINOM, 2001.
Figurnov V.E. IBM PC for the user. M., 2003.
Biryukov V. Increase the speed // Computer. - 2004. - No. 5.
Simonov S. Seven thousand two hundred // Computer. - 1999. - No. 32.
Tishin A.M. The memory of modern computers. - M.: Moscow State University. Lomonosov, 2001.
Annex 1
Types of memory
Appendix 2
The main user characteristics of the RAM
|
Specifications |
Diskette |
Streamer tape |
|||||
|
Storage problem |
sunlight |
Demagnetization, various effects |
Stuck and tear |
Field influence |
|||
|
Shelf life: |
|||||||
|
Driver issues |
|||||||
|
Write errors |
|||||||
|
Rewrite cycles |
|||||||
|
Maximum capacity |
9,1 (5,25) |
||||||
|
Price of the device (on average, $) |
|||||||
|
Prevalence in the Russian Federation |
Super high |
Very low |
1 Modern information technologies and networks. Unit 2. - M .: Modern University for the Humanities, 2001. p. fifteen.
2 Hook. M. Hardware IBM PC. Encyclopedia. - St. Petersburg: Peter, 2001. 521.
3 Ugrinovich N. Computer science and information technology. - M .: BINOM, 2001. 91-98.
Devices Devices storage of information a computer. Internal and external memory ... References: 10 Theoretical task. Devices storage of information a computer. Internal and external computer memory ...
Device input of information
Coursework \u003e\u003e Computer Science... of information; mouse - deviceeasier entry of information to a computer, and other manipulative devices. TO devices input of information include the following devices ... implement the concept of personal storage of information. Modern hard drives ...
Device output of information (2)
Abstract \u003e\u003e Computer ScienceTopic " Devices output of information" The computer is universal device for processing of information. ... print, it is intended for storage data in the process of creating ... teams, as well as for temporary storage font outlines and other data. ...
Information encoded using natural and formal languages, as well as information in the form of visual and sound images, is stored in the human memory. However for long-term storage information, its accumulation and transmission from generation to generation are used carriers information.
Storage medium (information carrier) - any material object or medium used to store or transmit information.
The material nature of information carriers can be different: DNA molecules that store genetic information; paper on which texts and images are stored; magnetic tape on which sound information is stored; photo and film films on which graphic information is stored; memory chips, magnetic and laser disks on which programs and data are stored in a computer, and so on.
All storage media are used for: recording, storage, reading, transmission of information. Until recently, paper was the most common medium of information. But time goes on, and the quality of paper has ceased to suit the modern society, preoccupied with an increasing and increasing amount of information.
According to experts, the amount of information recorded on various media exceeds one exabyte per year (1018 bytes / year). About 80% of all this information is stored in digital formon magnetic and optical media, and only 20% on analog media (paper, magnetic tapes, photo and film films).
Any computer information on any medium is stored in binary (digital) form. Regardless of the type of information (text, graphics, sound) - its volume can be measured in bits and bytes.
Digital storage media - devices for recording, storing and reading information presented in digital view.
On the first computers, paper media were used to digitally represent the input data - punched cards (cardboard cards with holes) and punched tapes.
Magnetic digital media of information
In the 19th century, magnetic recording was invented. Initially, it was used only for storing sound.
On computers of the first and second generations, magnetic tape was used as the only type of removable media for external memory devices. Approximately 500 KB of information was placed on a single coil with magnetic tape.
Since the early 1960s, magnetic disks have appeared: aluminum or plastic disks coated with a thin magnetic powder layer several microns thick. Information on the disk is located on circular concentric tracks.
A device that provides for writing / reading information is called an information storage device or drive. Magnetic disks are hard and flexible, removable and built-in to the drive of a computer (traditionally called hard drives).
Magnetic principle of writing and reading information
In floppy disk drives (HDD) and hard disk drives (HDD), or hard drives, the basis for recording information is magnetization of ferromagnets in a magnetic field, information storage is based on the conservation of magnetization, and information reading is based on the phenomenon electromagnetic induction.
In the process of recording information on flexible and hard magnetic disks, the head of the drive with a core of magnetically soft material (low residual magnetization) moves along the magnetic layer of the magnetically rigid carrier (large residual magnetization). A sequence of electrical pulses (a sequence of logical units and zeros) that create a magnetic field in the head are supplied to the magnetic head. As a result, elements of the surface of the carrier are sequentially magnetized (logical unit) or not magnetized (logical zero). When reading information when the magnetic head moves above the surface of the carrier, the magnetized sections of the carrier cause current pulses in it (the phenomenon of electromagnetic induction). The sequences of such pulses are transmitted along the trunk to random access memory a computer.
In the absence of strong magnetic fields and high temperatures, the elements of the carrier can retain their magnetization for a long time (years and decades).
Floppy disks
Until recently, personal computers were equipped with a floppy disk drive (HDD), which in the price lists is called FDD - Floppy Disk Drive (floppy disk drive). Floppy disks themselves are called floppy disks. The most common type of floppy disk with a diameter of 3.5 inches (89 mm) holds 1.44 MB of information.
The 3.5-inch floppy disk itself with a magnetic layer deposited on it is enclosed in a hard plastic envelope that protects the floppy disk from mechanical damage and dust.
For access of magnetic read-write heads to a diskette, there is a slot in its plastic case, which is closed by a metal valve. The valve automatically slides when a floppy disk is inserted into the drive.
In the center of the diskette there is a device for capturing and ensuring rotation of the disk inside the plastic case. The diskette is inserted into the drive, which rotates it at a constant angular speed. In this case, the magnetic head of the drive is installed on a specific concentric track of the disk (track), onto which recording is made or from which information is read.
Both sides of the floppy disk are covered with a magnetic layer and each side has 80 concentric tracks (tracks) for recording data. Each track is divided into 18 sectors, and in each sector you can write a data block of size 512 bytes.
When performing read or write operations, the diskette rotates in the drive, and the read-write heads are installed on the desired track and gain access to the specified sector.
The speed of writing and reading information is about 50 Kb / s. The diskette rotates in the drive at a speed of 360 rpm.
In order to save information, flexible magnetic disks must be protected from exposure to strong magnetic fields and heat, since such physical effects can lead to demagnetization of the medium and loss of information.
Floppy disks are currently discontinued.
Hard disk drives
A hard disk drive (HDD) or, as it is often called, a hard drive or hDD (Hard disk), is the main place to store data in personal computer. In the price lists, hard drives are indicated as HDD - Hard disk drive(Hard disk drive).
The origin of the name "Winchester" has two versions. According to the first, IBM developed a hard disk drive, on each side of which 30 MB of information fit, and which had the code name 3030. Legend has it that the Winchester 3030 rifle conquered the West. The developers of the device had the same intentions.
According to another version, the name of the device comes from the name of the city of Winchester in England, where IBM developed a technology for manufacturing a floating head for hard drives. Thanks to its aerodynamic properties, the read / write head made by this technology floats in the air stream that is formed during the fast rotation of the disk.
Winchester represents one or several hard (aluminum, ceramic or glass) disks placed on one axis, coated with magnetic material, which together with read-write heads, electronics and all the mechanics necessary for disk rotation and head positioning are enclosed in a sealed sealed enclosure.
Mounted on a motor spindle, disks rotate at high speed (7,200 rpm), and the information is read / written by magnetic heads, the number of which corresponds to the number of surfaces used to store information.
The speed of writing and reading information from hard drives is quite high - it can reach 300 MB / s.
Capacity of modern hard drives (as of November 2010) reaches 3,000 GB (3 Terabytes).
Portable hard drives exist - they are not installed inside the system unit, but are connected to the computer through a parallel port or through uSB port.
Hard disks use rather fragile and tiny elements (carrier plates, magnetic heads, etc.), therefore, in order to preserve information and performance hard disks it is necessary to protect from impacts and sharp changes in spatial orientation during operation.
Plastic cards
In the banking system, plastic cards are widely used. They also use the magnetic principle of recording information with which ATMs, cash registers, connected with the information banking system work.
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This topic belongs to the section:
Computer science
Answers to offset. Computer science as a scientific discipline. The concept of information. Information services and products. Information law offenses. Discrete (digital) presentation of information. The principle of the computer.
This material includes sections:
Computer science as a scientific discipline
Concept of information
Informatization. Computerization. The role of information activity in modern society
Information Revolution. Industrial society
Information society. Information culture
Society Information Resources
Information services and products. Stages of development of technical means and information resources
Types of professional human information activities using technical means and information resources
Legal norms related to information, offenses in the information sphere, measures to prevent them
Information
(from lat informatio - “clarification, presentation, awareness”) - information about something, regardless of the form of their presentation.
Types of Information:
- Sound
- Text
- Numeric
- Video information
- Graphic
Graphic
The first view, for which a method of storing information about the surrounding world in the form of cave paintings, and later in the form of paintings, photographs, diagrams, drawings on paper, canvas, marble and other materials depicting pictures of the real world, was implemented.
Sound
- the world around us is full of sounds and the task of their storage and replication was solved with the invention of sound recorders in 1877. Its kind is music information - for this type of encoding method using special characters was invented, which makes it possible to store it similarly to graphic information.
Text
- a method of encoding human speech with special characters - letters, and different peoples have different languages \u200b\u200band use different sets of letters to display speech.
Numeric
- A quantitative measure of objects and their properties in the environment. Similarly to textual information, the coding method is used to display it with special characters - numbers, and the coding (numbering) systems can be different.
Storage medium
- any material object or medium that is capable of storing information recorded in / on it in its structure for a sufficiently long time. A storage medium can be any object from which reading (reading) of the information available on it is possible.
Types of digital storage media:
- Tape media
- Floppy Drives
- Hard Disk Drives
- Optical disc drives
- Flash memory
Magnetic tape
- a magnetic recording medium, which is a thin flexible tape consisting of a base and a magnetic working layer. The working properties of a magnetic tape are characterized by its sensitivity during recording and signal distortion during recording and playback.
Diskette
- portable magnetic storage medium used for multiple recording and storage of relatively small data. Typically, a floppy disk is a flexible plastic plate coated with a ferromagnetic layer. This plate is placed in a plastic case that protects the magnetic layer from physical damage.
HDD
- a random access memory device based on the principle of magnetic recording. It is the main data storage device in most computers. The capacity of modern hard drives reaches 4000 GB (4 terabytes) and is close to 5 TB.
Optical discs usually have a polycarbonate or glass heat-treated base. The information surface of the optical discs is covered with a millimeter layer of durable transparent plastic (polycarbonate). In the process of recording and playback on optical discs, the role of the signal converter is played by the laser beam. The information capacity of an optical disk reaches 1 GB (with a disk diameter of 130 mm) and 2-4 GB (with a diameter of 300 mm).
