Record information on magnetic and optical media. Magnetic information media, their types. Data Structure on Disk
ATTENTION!Here is a very shortened text of the abstract. Full version Essay on computer science can be downloaded for free on the link indicated above.
Types of media information
Media information - Physical environment directly storing information. The main carrier of information for a person is its own biological memory (human brain). Human memory can be called RAM. Here the word "Operational" is synonymous with the word "fast". Accidental knowledge is reproduced by a person instantly. We can still be called internal memory, because its carrier is the brain - is inside us.
Media information - A strictly defined part of a specific information system that serves for intermediate storage or information transmission.
The basis of modern information technologies is a computer. When we are talking ABOUT AUM, then we can talk about media of information, as about external storage devices (external memory). These information media can be classified according to various features, for example, by type of execution, the material from which the carrier is made, and the like. One of the options for the classification of media is presented in Fig. 1.1.
List of information media in Fig. 1.1 is not exhaustive. Some media we consider in more detail in the following sections.
Ribbon media information
Magnetic tape - Magnetic recording medium, which is a thin flexible tape consisting of the base and magnetic working layer. The working properties of the magnetic tape are characterized by its sensitivity when recording and distorting the signal in the process of recording and playback. The most widely used multilayer magnetic tape with a working layer of needle particles of magnetically solid powders of gamma-oxide oxide (U-FE2O3), chromium dioxide (CRO2) and iron oxide, modified by cobalt, oriented in the direction of magnetization during recording.
Disc media information
Disc media information Refer to motor media with direct access. The concept of direct access means that the PC can "contact" to the track on which a plot with the search for information begins or where new information needs to be recorded.
Drives on disks are most diverse:
- Drives on flexible magnetic disks (NGMD), they are floppy disks, they are floppy disks
- Storage devices on hard magnetic disks (NGMD), they are hard drives (people are simply "screws")
- Drives on optical CDs:
- CD-ROM (Compact Disk Rom)
- DVD-ROM
Drives on flexible magnetic disks
Some time ago, floppy disks were the most popular means of transferring information from a computer to a computer, since the Internet in those times was very rare, computer networks Also, the devices for reading-write CDs were very expensive. Dakes are now used, but quite rarely. Mainly for storing various keys (for example, when working with the client-bank system) and to transfer various reporting information to state supervisory services.
Diskette - Portable magnetic information media used for multiple recording and storage of data relatively small volume. This type of carrier was especially common in the 1970s - early 2000s. Instead of the term "floppy", the abbreviation of GMD is sometimes used - "flexible magnetic disk" (respectively, a device for working with floppy disks is called NGMD - "Drive on flexible magnetic disks", a slang version - flopoveod, flopic, floppic from English floppy-disk or generally " Pokenishka "). The diskette is usually a flexible plastic plate covered with a ferromagnetic layer, hence the English name "FLOPPY DISK" (" flexible disk"). This plate is placed in a plastic housing that protects the magnetic layer from physical damage. The shell is flexible or durable. Recording and reading floppy disk is carried out using a special device - Drive (floppy drive). The diskette usually has a write protection feature by which you can provide data access only in read mode. Appearance 3.5 "floppy disks is shown in Fig. 1.2.
Storage drives on hard magnetic disks
Winchester type drives were widely distributed as storage devices in hard magnetic disks.
Term winchester It originated from the jargon name of the first model of a hard disk with a capacity of 16 kV (IBM, 1973), which had 30 tracks in 30 sectors, which accidentally coincided with a caliber of the 30/30 of the well-known Hunting rifle "Winchester".
Optical drives
CD ("CD", "Shape CD", "CD-ROM", "CD ROM") - an optical medium of information in the form of a disc with a hole in the center, information from which is read with a laser. Initially, the CD was created for digital storage audio (T.N. Audio-CD), however, is currently widely used as a wide-purpose storage device (T.N. CD-ROM). The format audio-compact discs differ from the CDs with data, and the CD players can usually play only them (on the computer, of course, you can read both types of disks). There are discs containing both audio information and data - they can be listed on the CD player, and read on the computer.
Optical disks These are usually polycarbonate or glass heat-treated base. Working layer optical disks Made in the form of the finest film of low-melting metals (televour) or alloys (tellur-selenium, teleurur-carbon, tellur-selenium-lead, etc.), organic dyes. The information surface of the optical disks is covered with a millimeter layer of durable transparent plastic (polycarbonate). In the process of recording and playback on optical disks The signal of the signal converter performs a laser beam focused on the working layer of the disk in a spot with a diameter of about 1 μm. When the disk is rotated, the laser beam follows the disk path, the width of which is also close to 1 μm. The possibility of focusing the beam in a small size stain allows you to form a label on the disk with an area of \u200b\u200b1-3 microns. Lasers (argon, helium-cadmium, etc.) are used as a light source. As a result, the record density is several orders of magnitude higher than the limit provided by the magnetic method of recording. The information capacity of the optical disk reaches 1 GB (with a diameter of a disk 130 mm) and 2-4 GB (with a diameter of 300 mm).
Widespread use as a carrier of information also received magneto-optical CDs Type RW (Re Writeble). On them record information is carried out by a magnetic head with the simultaneous use of the laser beam. The laser beam heats the point on the disk, and the electromagnet changes the magnetic orientation of this point. Reading is performed by a laser beam of less power.
In the second half of the 1990s, new, very promising media of documented information - digital universal video dVD discs (Digital Versatile Disk) type DVD-ROM, DVD-RAM, DVD-R with a high capacity (up to 17 GB).
According to optical technology, magneto-optical and digital CDs are divided into 3 main classes:
- Discs with permanent (unstable) information (CD-ROM). These are plastic CDs with a diameter of 4.72 inches and a thickness of 0.05 inches. They are made using a glass disk-original, which is applied to the photo-register layer. In this layer, the laser recording system forms a system of a pit (labels in the form of microscopic depressions), which is then transferred to replicable copies disks. Reading information is also carried out by a laser beam in optical drive personal computer. CD-ROM usually possess a capacity of 650 MB and are used to record digital audio programs, software for computer, etc.;
- Disks that allow one-time recording and multiple signal playback without the possibility of erasing (CD-R; CD-WORM - WRITE-ONE, read-MANY - recorded once). Used B. electronic archives and bank banks external drives COMPUTER. They represent the basis of a transparent material on which the working layer is applied;
- Reversing optical discs that allow multiple times, play and erase signals (CD-RW; CD-E). These are the most versatile discs capable of replacing magnetic media in almost all applications. They are similar to discs for a single record, but contain a working layer in which the physical recording processes are reversible. The manufacturing technology of such disks is more complicated, so they cost more discs for a single record.
Electronic media information
Generally speaking, all the carriers discussed earlier are also indirectly associated with electronics. However, there is a type of media where information is not stored on magnetic / optical disks, but in memory chips. These chips are made on Flash technology, so such devices are sometimes called Flash disks (the people are simply "flash drive"). The chip, as you can guess, is not a disc. However, operating systems media information with Flash memory are defined as a disk (for user convenience), so the name "disk" has the right to exist.
Flash memory (eng. Flash-Memory) is a type of solid-state semiconductor non-volatile rewritable memory. Flash memory can be read as much as possible, but it is possible to write in such a memory only a limited number of times (usually about 10 thousand times). Despite the fact that there is such a restriction, 10 thousand overwriting cycles are much more than able to withstand a floppy or CD-RW. Erasing occurs in areas, so you cannot change one bit or byte without overwriting the entire site (this restriction refers to the most popular flash memory for today - Nand). The advantage of flash memory over the usual is its non-volatility - when the energy is turned off, the memory content is saved. The advantage of flash memory over hard drives, CD-ROM-AMI, DVD is the lack of moving parts. Therefore, flash memory is more compact, cheap (taking into account the cost of read-write devices) and provides faster access.
Data storage
Data storage - This is a way to disseminate information in space and time. The storage method depends on its carrier (the book is the library, the picture is a museum, a photo - album). This process is the same ancient as the life of human civilization. Already in ancient times, a person faced the need to store information: scourings on trees, so as not to get lost during the hunt; account of objects with the help of pebbles, nodules; An image of animals and episodes of hunting on the walls of the caves.
EUM is designed for compact storage of information with the ability quick access To her.
Information system - This is a storage of information provided by the input procedures, search and placement and issuing information. The presence of such procedures is the main feature of information systems that distinguish them from simple clusters of information materials.
From information to data
A person is somewhat approaches the storage of information. It all depends on how much and how long it needs to be stored. If information can be remembered a bit in mind. It is easy to remember the name of your friend and his last name. And if you need to remember its phone number and the home address we use the notebook. When information is remembered (saved) it is called data.
Data in the computer has a different purpose. Some of them are needed only for a short period, others must be stored for a long time. Generally speaking, in the computer there are quite a lot of "cunning" devices that are designed to store information. For example, processor registers, register cache, and the like. But most of the "mere mortals" did not even hear such "terrible" words. Therefore, we restrict ourselves random access memory (RAM) and permanent memory to which the media has already considered.
Computer RAM
As already mentioned, there are several funds for storing information in the computer. Most fast way Remember the data is to write them into electronic chips. Such memory is called RAM. RAM consists of cells. In each cell, one byte of data can be stored.
Each cell has its own address. We can assume that it is like a cell number, so such cells are also called targeted cells. When the computer sends data storage data into RAM, it remembers the addresses to which these data are placed. Turning to the address cell, the computer finds in it byte data.
RECORDING RAM
The address cell of the RAM stores one byte, and since the byte consists of eight bits, then there are eight bite cells. Each bit cell of the RAM microcircuit stores an electric charge.
Charges cannot be stored in cells for a long time - they "flow". In just a few tenths of a second, the charge in the cell decreases so much that the data is lost.
Disk memory
For constant data storage, media are used (see the section "Views of information carriers"). CD and floppy disks have a relatively small speed, therefore most of the information to which permanent access is needed is stored on the hard disk. All information on the disk is stored as files. To control access to information, there is a file system. There are several types of file systems.
Data Structure on Disk
So that the data could not only write on hDD, and then read, you need to know exactly what and where it was recorded. All data should have an address. Each book in the library has its own room, rack, shelf and an inventory number - this is how its address. At this address, the book can be found. All data that is recorded on the hard disk should also have the address, otherwise they do not find them.
File Systems
It is worth noting that the data structure on the disk depends on the type of file system. All file systems consist of the structures necessary for storing and managing data. These structures usually include the boot record of the operating system, directories and files. The file system also executes three main features:
- Tracking and free space
- Support for catalog names and files
- Tracking the physical location of each file on the disk.
- FAT (File Allocation Table)
- FAT32 (File Allocation Table 32)
- NTFS (New Technology File System)
- HPFS (High Performance File System)
- NetWare File System.
- Linux Ext2 and Linux SWAP
Fat.
FAT file system is used by DOS, Windows 3.x and Windows 95. The FAT file system is also available in Windows 98 / ME / NT / 2000 and OS / 2.
The FAT file system is implemented using File Allocation Table (FAT - file distribution tables) and clusters. Fat is the heart of the file system. Fat has a duplicate to protect its data from random erase or malfunction. Cluster - the smallest unit systems FAT. For data storage. One cluster consists of a fixed number of the disk sectors. Fat is recorded which clusters are used which are free, and where the files are located within clusters.
FAT-32.
FAT32 - file system that can be used Windows 95 OEM Service Release 2 (version 4.00.950b), Windows 98, Windows Me and Windows 2000. However, DOS, Windows 3.x, Windows NT 3.51 / 4.0, earlier versions of Windows 95 And OS / 2 does not recognize FAT32 and cannot load or use files on the disk or FAT32.
FAT32 - Development of the FAT file system. It is based on a 32-bit file distribution table, faster than 16-bit tables used by the FAT system. As a result, FAT32 supports discs or sections of much larger size (up to 2 TB).
NTFS
NTFS (New File System Technology) is available only Windows NT / 2000. NTFS is not recommended to use less than 400 MB on disks, because it requires a lot of space for system structures.
The central structure of the NTFS file system is MFT (Master File Table). NTFS saves many copies of the critical part of the table to protect against malfunctions and data loss.
Hpfs.
HPFS (High Performance File System) - a preferred file system for OS / 2, which is also supported by senior windows versions NT.
Unlike FAT file systems, HPFS sorts its directories based on file names. HPFS also uses a more efficient structure for organizing a catalog. As a result, access to the file is often faster and the place is used more efficiently than with the FAT file system.
HPFS distributes file data in sectors, not in clusters. To save a track that has sectors or not used, HPFS organizes a disk or partition in the form of groups of 8 MB. Such a grouping improves performance, because the read / write heads should not return to the zero track every time the OS needs access to information about the available location or location of the required file.
NetWare File System.
The Novell NetWare operating system uses the NetWare file system, which was designed specifically for use by NetWare.
Linux Ext2 and Linux SWAP
Linux EXT2 and Linux file systems were designed for Linux OS (UNIX version for free distribution). The Linux EXT2 file system supports a disk or a maximum size of 4 TB.
Catalogs and file path
Consider for the example the structure of the FAT disk space system, as the simplest.
The information structure of the disk space is the external representation of the user-oriented disk space and defined by such elements as the volume (logical disk), the directory (folder, directory) and the file. These elements are used when communicating the user with the operating system. Communication is carried out using commands that perform access operations and directories.
Information sources
- Computer science: textbook. - 3rd recreation. ed. / Ed. N.V. Makarova. - M.: Finance and Statistics, 2002. - 768 p.: Il.
- Wolf V.K. Investigation of the functional structure of the memory of a personal computer. Laboratory workshop. Tutorial. Publishing House of Kurgan State University, 2004 - 72 p.
The need to keep any information in humans appeared in prehistoric times, which is a bright example - rock painting, which has been preserved to this day. Fashionable drawings can be rightfully called the most wear-resistant carrier of information on this momentAlthough there are some difficulties with portability and ease of use. With the advent of computer (and PC in particular), the development of capacious and convenient information in the use of media became particularly relevant.
Paper media
In the first computers, punch cards and perforated paper tape wound on reels, the so-called perflector. Its progenitors were automated weaving machines, in particular the jacquer machine, the final version of which was created by the inventor (in honor of which it was named) in 1808.For automation of the filament process, perforated plates were used:
Perfoocards - cardboard cards that used similar method. There were many varieties, as with holes that were responsible for "1" in binary codeand text type. The most common was the IBM format: the map size was 187x83 mm, the infatomation was located in 12 lines and 80 columns. In modern terms, one perfocard kept 120 bytes of information. To enter information, the cards needed to be supplied in a specific sequence.
Perflate uses the same principle. The information is stored on it in the form of holes. The first computers created in the 40s of the last century worked both with a real-time perflective in real time data, and used a certain semblance of RAM, mainly using electron-ray tubes. Paper media were actively used in 20-50 years, after which they gradually began to be replaced with magnetic carriers.
Magnetic carriers
In the 50s, the active development of magnetic carriers began. The basis was the phenomenon of electromagnetism (the formation of the magnetic field in the conductor when passing the current through it). The magnetic carrier consists of a surface covered with a ferromagnet and read / writing head (core with winding). The winding flows the current, the magnetic field of a certain polarity appears (depending on the direction of the current). The magnetic field affects the ferromagnet and magnetic particles in it are polarized in the direction of field action and create residual magnetization. To write data to different parts, the magnetic field of different polarity is performed, and when reading the data zones are recorded, in which the direction of residual magnetization of the ferromagnet is changed. The first carriers were magnetic drums: large metal cylinders covered with ferromagnet. There were also reading heads around them.
After them, a hard disk appeared in 1956, it was an IBM 305 Ramac, which consisted of 50 cm with a diameter of 60 cm, was commensurate with a large refrigerator of the modern Side-BY-SIDE format and weighed a little less than a ton. Its volume was incredible at the time of 5 MB. The head moved freely on the surface of the disk and the speed of work was higher than that of magnetic drums.Loading process 305 Ramac in plane:
The volume quickly began to increase and at the end of the 60s IBM has released a high-speed drive with two discs with a capacity of 30 MB. Manufacturers actively worked on a decrease in dimensions and by 1980 a hard disk had a size of a 5.25-inch drive. Since those times, the design, technology, volume, density and dimensions have undergone colossal changes and the most popular steel form factor and 3.5, 2.5 inches, at least 1.8 inches, and the volumes already reach a dozen terabyte on one carrier.
For some time, the IBM MicroDrive format was used, which was a miniature hard disk in the form factor of the CompactFlash memory card type II. Released in 2003, later sold by Hitachi.
In parallel, the magnetic tape developed. She appeared together with the release of the first American commercial computer Univac I in 1951. Again, IBM has been tried again. The magnetic tape was a thin plastic strip with magnetically sensitive coating. Since those times used in various form factors.
Starting with reels, tape cartridges and ending with CDs and VHS video cassettes. In computers were used since the 70s and ending between the 90s (already in significantly smaller quantities). Often in quality external carrier A connected tape recorder was used to the PC.
Magnetic tape drives called streamers apply and now, mainly in industry and large business. At the moment, standard boobies are used. LINEAR TAPE-OPEN (LTO), and record this year set IBM and Fujifilm, managed to record on the standard Bobin of 154 terabyte information. Previous record - 2.5 Terabyte, LTO 2012.
Another type of magnetic media is a floppy disk or floppy disk. Here the layer of ferromagnet is applied to the flexible, light basis and placed in the plastic case. Such carriers were simple from the point of view of manufacture and differed in a low cost. The first diskette had a form factor of 8 inches and appeared at the end of the 60s. Creator - again IBM. By 1975, the container reached 1 MB. Although the popularity of the floppy disk has earned due to IBM, which founded their own company. Shugart Associates and in 1976 released a 5.25 inches format diskette, the container was 110 kb. By 1984, the capacity was already 1.2 MB, and Sony had a charter with a more compact 3.5-inch formator. Such floppy disks can still be found at many at home.
IOMEGA has released in the 1980s cartridges with Bernoulli Box magnetic discs, 10 and 20 MB capacity, and in 1994 - the so-calledThe ZIP size of 3.5 inches of 100 MB, until the end of the 90s, they were actively used enough, but they were not to compete with CDs not on the teeth.
Optical carriers
Optical media have the form of disks, reading from them is carried out using optical radiation, usually laser. The laser beam is sent to a special layer and reflected from it. When reflected, the beam is modulated by the smallest recesses on a special layer, when registering and decoding these changes, the information recorded on the disk is restored. For the first time, the technology of optical recording using the light-resistant carrier was developed by David Paul Gregg in 1958 and patented in 1961 and 1990, and in 1969, Philips created the so-called LaserDisc in which the light reflected. For the first time, LaserDisc was shown in 1972, and he entered the sale in 1978. In size, he was close to vinyl records and was intended for films.
In the seventies, the development of optical carriers of a new sample began, as a result, Philips and Sony were presented in 1980 a CD format (Compact Disk), which was first demonstrated in 1980. On the sale of CDs and equipment received in 1982. Initially used for audio, it was placed up to 74 minutes. In 1984, Philips and Sony created a CD-ROM standard (Compact Disc Read Only Memory) for any data types. The volume of the disk was 650 MB, later - 700 MB. The first discs that could be recorded at home, and not at the factory were released in 1988 and received the nameCD-R (Compact Disc Recordable), andCD-RW, allowing multiple overwriting data on the disk, appeared already in 1997.
The form factor has not changed, the recording density increased. In 1996, DVD format (Digital Versatile Disc) appeared, which had the same shape and diameter of 12 cm, and the volume is 4.7 GB or 8.5 GB in two-layer. To work with DVD discs, appropriate drives back compatible with CD were released. In subsequent years, several more DVD standards were released.
In 2002, the world was presented two different and incompatible formats of new generation optical disks: HD DVD and Blu-Ray Disc (BD). In both cases, a blue laser with a long wave of 405 nm is used to record and read data, which made it possible to increase the density. HD DVD is capable of storing 15 GB, 30 GB or 45 GB (one, two or three layers), Blu-ray - 25, 50, 100 and 128 GB. The latter became more popular and 2008 TOSHIBA (one of the creators) refused HD DVD.
Semiconductor carriers
In 1984, Toshiba proposed semiconductor carriers, the so-called NAND flash memory, which became popular after the decade after the invention. The second NOR version was proposed by Intel in 1988 and is used to store software codes, such as BIOS. Nand memory is now used in memory cards, flash drives, SSD drives and hybrid hard drives.
Nand technology allows you to create high-density chips, it is compact, less energy-efficient to use and has a higher speed (in comparison with hard drives). The main minus at the moment is quite high cost.
Cloud storage
With the development of a worldwide network, increasing speeds and mobile Internet There are numerous cloud storage, in which the data is stored on numerous servers distributed on the network. Data is stored and processed in the so-called virtualthe cloud and the user has access to them in the presence of Internet access. Physically servers can be remotely from each other. There are both specialized services of the Dropbox type and options for manufacturers of software or devices. Microsoft - ONEDRIVE (formerly Skydrive), Apple ICloud Google Disc etc.
Physics report
on this topic:
"Magnetic recording.
Magnetic media information "
The technology of recording information on magnetic media appeared compared to it recently - approximately in the middle of the 20th century (40th - 50s). But already at least decades later - the 60s - 70s - this technology has become very raz-space throughout the world.
Very long ago, the first gram plate appeared. Which was used as a carrier of various audio data - was recorded on it various music melodies, human speech, songs.
The technique of recording on the record was rather simple. With the help of a special apparatus in a special soft-com material, vinyl, seeds, pits, stripes were made. And from this, there was a plastic tank, which could be heard using a special apparatus - patted or player. The patone consisted of: Mehanism, rotating the plate around his axis, needles and tubes.
The mechanism, a rotating plate, was operated, and the needle was put on the record. The needle smoothly sailed through the grooves drove into the record, while making various sounds - depending on the depths of the groove, its width, tilt, etc., using the phenomenon of resonance. And after the pipe, which was near the needle itself, increased the sound, "carved" with a needle. (Fig. 1)
Almost the same system and used in modern (and used earlier too) devices for reading a magnetic recording. The functions of the composite hour remained the same, only the components themselves were changed - instead of the vinyl plates, tapes are used with a layer of magnetic particles on top; And instead of a needle - a special reader. A tube that enhances the sound disappeared at all, and the speakers use the new technology to reproduce and enhance the sound oscillations to its place. And in some industries in which magnetic media are used (for example, in the compendges) disappeared the need to use such tubes.
The magnetic tape consists of a strip of a dense substance, to which a layer of ferromagnets is sprayed. It is on this layer "remembered" information.
The recording process is also similar to the pro-Cesss records for vinyl records - with the help of a magnetic induction appearance on something special machine.
A current is served on the head, which at-lead a magnet. The recording of the sound on the film is due to the action of the electromagnet on the film. The magnetic field of the magnet changes to the tact with sound oscillations, and thanks to this, small magnetic particles (domains) begin to change their location on the surface of the film in a certain order, in the inspence of the effects of the magnetic field created by the electromagnet.
And when playing a recording, the recording recording is observed: the NAMA-niche tape excites the electrical signals in the magnetic head, which after the amplification go further into the speaker. (Fig. 2)
The data used in computer technician, recorded on magnetic media in the same way, with the difference that you need less space on the film than for the sound. Just all the information recorded on the magnetic wear-tel in computers is written in binary system - If, when reading from carrying a head, "feels" to find a domain under him, then this means that the value of this data particle is "1", if not "feels", then the value is "0". And then the computer system already converts the data recorded in the binary system to a more understandable system.
Now there are many different types of magnetic media in the world: floppy disks, audio and video tapes, Babine ribbons, hard drives inside computers I.T.D.
But the new laws of physics are gradually opening, and together with them - new features of information recording. Already a few decades ago, many of the carriers of information based on the new technology appeared - reading information with the help of lenses and a laser beam. But still, the magnetic record technology exists even for quite a long time due to its ease of use.
Information medium (information carrier) is any material object used by a person for storing information. This may be, for example, stone, wood, paper, metal, plastics, silicon (and other types of semiconductors), tape with magnetized layer (in bobins and cassettes), photo material, plastic with special properties (eg, in optical disks) and etc., etc.
The information carrier may be any object from which it is possible to read (read) available on it.
Media information apply to:
- records;
- storage;
- reading;
- transmission (distribution) of information.
Often, the information carrier itself is placed in a protective sheath that increases its safety and, accordingly, reliability of information conservation (for example, paper sheets are placed in a cover, a memory chip - in plastic (smart card), magnetic tape - in the housing, etc.) .
Electronic media include carriers for single or multiple recording (usually digital) by electrically:
- optical discs (CD-ROM, DVD-ROM, Blu-Ray Disc);
- semiconductor (flash memory, floppy disks, etc.);
- CDs (CD - Compact Disk, CD), which can be written to 700 MB of information;
- DVDs (DVD - Digital Versatile Disk, digital universal disk), which have a significantly greater information capacity (4.7 GB), as optical tracks on them have a smaller thickness and are placed more tightly;
- hR DVD and Blu-Ray discs, the information capacity of which is 3-5 times higher than the information container of the DVD discs due to the use of a blue laser with a wavelength of 405 nanometers.
Electronic media have significant advantages over paper (paper sheets, newspapers, logs):
- in terms of volume (size) stored information;
- at the specific storage value;
- on the efficiency and efficiency of the provision of the relevant (intended for not long-term storage) information;
- if possible, the provision of information in the form, convenient to the consumer (formatting, sorting).
There are disadvantages:
- fragility of reader devices;
- weight (mass) (in some cases);
- dependence on power supply sources;
- the need for a read / write device for each type and media format.
Hard Magnetic Drive or HDD (Eng. Hard (Magnetic) Disk Drive, HDD, HMDD), Hard Drive - Storage Device (Information Storage Device) based on the principle of magnetic record. It is the main data storage in most computers.
Unlike the "flexible" disk (flop), information in the NLCD is recorded on rigid plates coated with a layer of ferromagnetic material - magnetic discs. The NZHMD uses one or more plates on one axis. The reading heads in the working mode do not touch the surface of the plates due to the layer of the incident air flow, which is formed at the surface with a rapid rotation. The distance between the head and the disk is several nanometers (in modern disks about 10 nm), and the lack of mechanical contact provides a long service life of the device. In the absence of rotation of the disc drives, there are a spindle or outside the disk in a safe ("parking") zone where their abnormal contact with the surface of the discs is excluded.
Also, unlike a flexible disc, the media is usually combined with a drive, drive and electronics block. Such hard drives are often used as a carrier of information.
Optical (laser) discs are currently the most popular media. They use the optical principle of recording and reading information using a laser beam.
DVDs can be two-layer (Capacity 8.5 GB), while both layers have a reflective surface carrying information. In addition, the information container of DVDs can be even doubled (up to 17 GB), since information can be recorded on two sides.
Optical drive drives are divided into three types:
- without recording options - CD-ROM and DVD-ROM (ROM - Read Only Memory, read-only memory). On CD-ROM and DVD-ROM drives, information is stored that was recorded on them during the manufacturing process. The recording on them is not possible;
- with a single recording and multiple reading - CD-R and DVD ± R (R - Recordable, recorded). On CD-R and DVD ± R disks, information can be recorded, but only once;
- with the ability to overwrite - CD-RW and DVD ± RW (RW - Rewritable, overwritten). On CD-RW and DVD ± RW disks, information can be recorded and erased repeatedly.
The main characteristics of optical drives:
- disk capacity (CD - up to 700 MB, DVD - up to 17 GB)
- the speed of data transmission from the carrier into RAM - is measured in shares, multiple speed 150 KB / s for CD drives;
- access time - the time required to search for information on the disk is measured in milliseconds (for CD 80-400 ms).
Currently, 52x-high-speed CDs received widespread - up to 7.8 MB / s. The CD-RW recording of the disks is performed at a lower speed (for example, 32x-multiple). Therefore, the CDs are marked with three numbers "reading speed x CD-R recording speed CD-RW" (for example, "52x52x32").
DVD drives are also marked with three numbers (for example, "16x8x6").
Personal storage rules (storage in vertical) and operation (without scratching and contamination) optical media can save information for decades.
Flash Memory - refers to electrically reprogrammed memory semiconductors (EEPROM). Thanks technical solutions, low cost, large volume, low power consumption, high speed, compactness and mechanical strength, flash memory are embedded in digital portable devices and media. The main advantage of this device is that it is non-volatile and it does not need electricity for data storage. All the stored information in flash memory can be considered an infinite number of times, but the number of full recording cycles, unfortunately, is limited.
Flash memory has as its advantages in front of other drives ( hard drives and optical drives)And its drawbacks you can get acquainted from the table below.
| Type of drive | Benefits | disadvantages |
| HDD | Large volume of stored information. High speed. Lowest data storage (per 1 MB) | Large dimensions. Sensitivity to vibration. Noise. Heat out |
| Optical disk | Ease of transportation. Cheap information storage. Ability to replicate | Small volume. You need a reader. Restrictions on operations (reading, writing). Low speed. Sensitivity to vibration. Noise |
| Flash memory | High data access speed. Economic power consumption. Resistance to vibrations. Convenience connection to a computer. Compact sizes | Limited number of recording cycles |
Drives on magnetic and optical media.
Let's call the reasons for the need for external memory from the computer.
1. Saving information for subsequent use or to transmit to other people was of great importance for the development of civilization. Before the appearance of a computer, a man used for this purpose books, photographs, tape recorders, film, etc. By the end of the 20th century, information flows increased significantly and the appearance of a computer contributed to the development and use of information carriers ensuring the possibility of its long-term storage in compact form.
2. ECM RAM has a number of shortcomings related to its manufacturing technology. Even today, in the XXI century it does not have a large enough volume and does not accommodate huge amounts of information. In addition, the contents of RAM are still lost when the computer is turned off. Therefore, the presence of B. computer system Another type of memory - external, made it possible to eliminate these disadvantages. The main function of the external memory is the ability to continually store information. In addition, the external memory has a large volume and cheaper operational. And also, external memory media ensure the transfer of information from one computer to another, which is important in a situation where there are no computer networks.
In this way external (long-term) memory - This is the location of long-term storage of data (programs, results of calculations, texts, etc.) not currently used in the computer's RAM. External memory, in contrast to the operational, is non-volatile, but does not have a direct connection with the processor.
External memory carriers, in addition, provide data transport in cases where computers are not combined on the network (local or global).
To work with the external memory requires drive(Devices providing entry and / or reading information) and storage devices - media.
Main types of drives:
Storage devices on flexible magnetic disks (NGMD);
Storage devices on rigid magnetic disks (NGMD);
CD-ROM drives, CD-RW, DVD. They correspond to the main types of media:
Flexible magnetic discs (Floppy.Disk);
Hard magnetic discs (HardDISK):
CD-ROM discs, CD-R, CD-RW, DVD. The main characteristics of drives and carriers:
Information container;
Information exchange rate;
Reliability of information storage;
Cost.
Principle work magnetic memorable devices
The magnetic record is based on the transformation of digital information (as 0 and 1) into an alternating electric current, which is accompanied by a variable magnetic field. As a result, the surface of the magnetic carriers is divided into non-magnetized sections (0) and magnetized (1).
In earlier generations, the functions of the external memory were performed perfumed and chapels, as well as magnetic ribbons that are now used very rarely. Magnetic tapes are a device with sequential access. Data can be read or recorded only sequentially, when the order is violated, it is necessary to wait a long time until the tape is rewound in the desired location. Magnetic tapes are sufficiently slow devices, albeit with a large capacity. Modern devices for working with magnetic ribbons - streamers have increased recording speed, and the container of one strider cassette is measured by hundreds and thousands of megabytes, and the data transfer rate is from 2 to 9 MB per minute.
Flexible disk
Drive on flexible magnetic disks (eng. Floppy Disk) or diskette - a carrier of a small amount of information, which is a flexible disk in a protective sheath. Used to transfer data from one computer to another and to distribute software.
Device diskette.
Shutter read / write window
Plastic envelope
Disc drive sleeve
Recording Lock: Disabled / Included
Disk is inside a plastic envelope that protects it from mechanical damage. In order to read or write data, you must insert a floppy disk to the drive for flexible magnetic disks, which is located on the front panel. system Block. Inside the disk drive, the read / write curtain automatically opens and it is above this place that the drive / recording head is installed. The disc inside the drive rotates with a constant angular velocity, which is low enough (somewhat kilobyte per second, the average access time is 250 ms). Recording information occurs on both sides of the disk. Currently, the most common floppy disks with a size of 3.5 inches (1 inch \u003d 2.54 cm) and a capacity of 1.44 MB (this is approximately 600 pages of text or several dozen graphic images). The disc can be protected from recording. This uses a safety latch.
Diskettes require accurate circulation. They may be damaged if:
Touch the recording surface;
Write on a diskette label with a pencil or ballpoint handle;
Flex a diskette
Overheat a floppy disk (leave in the sun or near the heating battery);
Magnetic field floppy disk.
Hard magnetic disk
Since a flexible disk has a small volume, it is mainly used to transfer information from one computer to another. The hard disk is an information warehouse of the computer and is able to store huge amounts of information.
Hard magnetic drive drive (eng. HDD - Hard Disk Driver) or Winchester is the most massive storage device of a high container in which aluminum plate carriers are aluminum plates, both surfaces of which are coated with a layer of magnetic material. Used for constant storage of programs and data.
Winchester discs are placed on one axis and together with the read / write heads and their heads are placed in a hermetically closed metal case. This design made it possible to significantly increase the speed of rotation of the disks and the record density. Recording information occurs on both surfaces of the disks.
Unlike a floppy disk, the hard disk rotates continuously. Therefore, its rotation speed can be from 3600 to 10,000 rpm, the average data search time is 9 ms, the average data transfer rate is up to 60 MB / s.
The capacity of the hard drives in computers 2000 was measured with dozens of gigabytes. The most common drives with a diameter of 2.2, 2.3, 3.14, 5.25 inches.
In order to preserve information and performance, the Winchester needs to be removed from shocks and sharp changes in spatial orientation during operation.
Laser disk
CD-ROM (eng.Compact.DISK.RealONLY.Memory - constant storage device based on a compact disc)
The CD with a diameter of 120 mm (about 4.75 inches) is made of polymer and covered with metal film. Information is read from this metal film, which is covered by a polymer protecting data from damage. CD-ROM is a one-sided medium of information.
The principle of digital record information on the laser disk differs from the principle of magnetic record. Encoded information is applied to the disk with a laser beam, which creates microscopic depressions on the surface, separated by flat areas. Digital Information It seems to be alternating the depression (zero encoding) and reflecting the light of islets (single coding). Information applied to the disk cannot be changed.
Reading information from the disk occurs due to the registration of changes in the intensity reflected from the aluminum layer of radiation of a low-power laser. The receiver or the photo sensor determines whether the beam reflected from the smooth surface (one is thus fixed), it was scattered or absorbed (fixing zero). The scattering or absorption of the beam occurs in places where the recovery was applied during the record. The photo sensor perceives the scattered ray, and this information in the form of electrical signals enters the microprocessor, which converts these signals into binary data or sound.
CD-ROM rotates with variable angular speed to provide a constant linear speed when reading. Thus, reading information from the internal sections of the disk is carried out with a greater number of revolutions than from the outer. Therefore, access to the data on the CD-ROM is carried out faster than the data on diskettes, but slower than on hard drives (from 150 to 400 ms at a rotational speed up to 4500 rpm). The data transfer rate is at least 150 KB and reaches 1.2 MB / s.
CD-ROM capacity reaches 780 MB, which is usually produced by multimedia programs.
CD-ROM is simple and convenient to work, have a low value storage value, practically not wear out, cannot be amazed by viruses, it is impossible to accidentally erase information.
CD-R (Compact Disk Recorder)
CD-R is a recordable disk capacity of 650 MB. On the disks CD-R, the reflective layer is made of a gold film. Between this layer and the basis there is a registering layer of organic material, dark with heating. In the process of recording, the laser beam heats the selected points of the layer, which darken and cease to skip the light to the reflective layer, forming areas similar to the valves. CD-R drives, thanks to a strong reduction, are becoming increasingly distributed.
CD-RW (Compact Disk Rewritable)
More popular are CD-RW drives that allow you to record and overwrite information. CD-RW drive allows you to record and read CD-R and CD-RW discs, read CD-ROM discs, i.e. is in a certain sense universal.
DVD abbreviation is decrypted as Digital.Versatile.Diski.e. uni.version digital disk.Having the same dimensions that the usual CD, and a very similar principle of operation, it accommodates extremely much information - from 4.7 to 17 GB. Perhaps it is because of a large capacity, it is called universal. True, today a DVD is actually applied only in two areas: for the storage of video films (DVD-Video or simply DVD) and super-abandoned databases (DVD-ROM, DVD-R).
The range of containers arises like this: unlike CD-ROM, DVDs are written on both sides. Moreover, on each side one or two layers of information can be applied. Thus, one-sided single-layer discs have a volume of 4.7 GB (they are often called DVD-5, i.e., the discs with a capacity of about 5 GB), double-sided single-layer - 9.4 GB (DVD-10), one-sided two-layer - 8.5 GBIT (DVD-9), and bilateral two-layer - 17 GB (DVD-18). Depending on the amount of data requiring storage and the DVD type is selected. If we are talking about movies, then two versions of one picture are often stored on bilateral disks - one widescreen, the second in the classic television format.
The main parameter of the CD-ROM drive is the speed of data reading. It is measured in multiple shares. The unit of measurement adopted the read speed in the first serial samples, which is 150 KB / s, so a double reading speed drive provides 300 KB / s capacity, with a quail - 600 kb / s, etc.
In order to preserve information, laser discs need to be protected from mechanical damage (scratches), as well as contamination.
Structure surface disc
Formulation of the problem.
Imagine a book made in the form of a long ribbon.
Is it convenient to look for the necessary information in such a "book"? Why?
What is the convenience of search necessary information In the usual book, in which there are pages? Why?
Output:in the book you can find the necessary information without problems, since it has a convenient structure, namely, divided into pages. In the book made in the form of a long ribbon, it is inconvenient to look for information, since it is not clear which part of the ribbon it is. Pages have their numbers, so it is enough to know the number of the page on which it is located, i.e. the book has a structure. Without this structure, the search for information is hampered.
Since the book is an analogue of external memory, the surface of any disk must have a certain structure. Also, as in the manufacture of books, a large sheet of paper is cut on the pages and then collect them together and the surface of the disk "cut" into parts - "Pages".
Magnetic discs.
Any magnetic disk is not ready for work. To bring it to the operating state, it must be formatted, i.e. the structure of the disk must be created. For a flexible magnetic disk is magneticconcentric paths - divided into sectors.And the hard magnetic disk is still present cylinderst. K. Hard disk consists of several plates.
The sector is a too small "piece" of the disk surface (as a string on the page). Therefore, the sectors are combined into larger "pieces" - clusters.
The volume of the disk can be calculated as follows.
Volume \u003d number of sides * Number of tracks * Sector * Sector volume.
The farther from the center of the disk, the tracks are longer. Therefore, with the same number of sectors on each of them, the recording density on the inner tracks should be higher than on external. The number of sectors, the sector capacity, and therefore, the information of the disk depend on the type of drive and formatting mode, as well as the quality of the disks themselves.
Laser disks
Unlike magnetic discs, the CD-ROM has only one physical path in the form of a helix, which comes from the outer diameter of the disk to the internal.
Example 1.Tree file structure of the disk. Capital scores are indicated by directory names, linear names.
List the names of catalogs of the 1st, 2nd, 3rd levels. Specify the path to the Letter file. TXT from root catalog. Specify the path to the letter1.doc file from the root directory, and to the letter2.doc file from the work directory. Specify full file names
|
letter. TXT and Letterl. DOC if the file structure is stored on the S. disk
Decision.Catalogs of the 1st level Computer, Work, Urok. 2 level catalogs - IBM, Apple, Document, Print. 3rd level catalogs - D0C1, D0C2.
Path to the Letter file. TXT from root catalog: \\ Work \\ Print. Path to the letterl file. Doc from root catalog: \\ W0RK \\ D0CUMENT \\ D0C2. The path to the letter2.doc file from the W0RK: \\ D0CUMENT \\ D0C2 directory.
Full names of LETTER files. TXT and Letterl. Doc:
C: \\ Work \\ Print \\ Letter. TXT. and
C: \\ W0RK \\ D0CUMENT \\ D0C2 \\ Letterl. DOC.
|
The tree of the hierarchical file structure on the magnetic disk is given. Capital letters indicated directory names, line - file names:
Find errors in the file structure.
The tree of the hierarchical file structure on the magnetic disk is given. Capital letters indicated directory names, line - file names:
List the catalogs of the 1st, 2nd, 3rd levels, if there are. Specify the paths from the root directory to each of the files.
\\ Country \\ USA \\ info \\ Culture. TXT.; \\ Country \\ USA \\ Washington. TXT.; \\ Country \\ russia \\ Moscow. TXT.; \\ Country \\ russia \\ info \\ industry. TXT.; \\ Country \\ russia \\ info \\ culture. TXT.
Paths from the root directory to some files stored on magnetic disk. Capital letters indicated directory names, line - file names: \\ Box \\ Letter \\ Peter. TXT.; \\ Box \\ letter \\ kate. TXT.; \\ Letter \\ work \\ April. TXT.; \\ Letter \\ work \\ may. TXT.; \\ Letter \\ Frend \\ School \\ Mary. TXT.; \\ Letter \\ Frend \\ Sport. TXT.. Display a file structure in the form of a tree.
Decide tasks: ■ № 1
A double-sided diskette has a volume of 800 KB. How many tracks on one side of the diskette, if each track contains 20 sectors of 0.5 kb. Decision".
1) 800: 2 \u003d 400 KB - volume of floppy disks;
2) 20 * 0.5 \u003d 10 KB - the volume of all sectors;
3) 400: 10 \u003d 40 - tracks. Answer:40 tracks.
What volume has each two-sided diskette sector with a capacity of 360 kB, if each side of the floppy disk is divided into 40 tracks on the 18 sectors on the track?
Decision:
1) 40 * 18 \u003d 720 sectors on the disk;
2) 360: 720 \u003d 0.5 KB - the sector volume. Answer:0.5 KB.
Paths from the root directory to some files stored on a magnetic disk are indicated. Capital letters indicated directory names, line - file names: \\ SPORT \\ SKI \\ RUSSIA. TXT.; \\ SPORT \\ SKI \\ GERMANY. TXT.; \\ SPORT \\ SKATE \\ FINLAND. TXT.; \\ COMPUTER \\ IBM \\ info \\ pentium. TXT.; \\ COMPUTER \\ info \\ IBM. TXT.. Display a file structure in the form of a tree.