Information recorded on an external storage medium is called. Computer RAM


For long-term storage of information in a computer, removable media are widely used, such as optical disks, flash memory, and an external hard drive.

Optical discs

Data can be stored on optical discs in CD format (from the English Compact Disc), with a capacity of up to 700 MB and DVD format discs (from the English Digital Versatile Disc - digital multi-purpose disk), with a capacity of up to 4.7 GB for single-layer discs (SL - Single Layer) and 7.9 GB for double-layer (DL – Double Layer).

In turn, optical discs are divided into disposable discs, which can be written only once - CD-R (or DVD-R) discs, and reusable discs, which can be rewritten multiple times - CD-RW (or DVD-RW) discs.

In computer jargon, blank discs without recording are called “blanks,” and the recording process is called “burning.” Used to read and write discs special device, called CD drive – DVD-ROM, which is installed in, the receiving tray of the device goes to the front panel of the system unit. DVD-ROM is universal device, allowing you to both read and write discs of both formats (CD and DVD). In order to place a disc in the drive, you need to press a button on its panel; a tray will slide out of the drive, onto which you need to place the disc, shiny side down. Then press the button again or lightly push the tray itself so that it closes.

Flash memory

Flash memory ( USB Flash drive). Now even the most distant person from computers has probably heard the word. This is flash memory. Today, flash drives are rapidly replacing optical disks due to ease of handling, memory capacity, writing and reading speed.

At the time of writing, flash drives with capacities from 4 GB to 128 GB are available for sale. The larger the capacity, the more expensive the flash drive. In addition, flash drives have different speed recording and reading, but in any case it is several times higher than that of optical disks.

To connect a flash drive to a computer, you just need to insert it into the USB connector (port) on the front or rear panel system unit.

Memory cards, familiar to us as storage media in smartphones and digital cameras, also belong to flash memory and can serve as removable storage in a computer. In this case, reading and writing data is performed by a card reader, which can be built into the system unit or connected to it via USB port. The capacity of memory cards varies from 4 GB to 128 GB.

An electronic storage medium is a device for storing, accumulating and transmitting information. IN personal computer used for this purpose internal storage information called hard drive or hard drive. The name “Winchester” appeared historically for the first hard drive created, some of the parameters of which turned out to be similar to the caliber of a hunting rifle.
In some cases, the computer user applies additional external devices for storing information.

Common external storage media are CDs. They will be divided into devices intended only for reading information already initially recorded on them, devices intended for one-time recording of information and further reading, and devices intended for repeated writing, erasing information and reading. The information is written to the CD in the form of files. The CD for recording is inserted into optical drive computer. Information on CDs is recorded using a laser.

Read-only CDs often contain educational programs of some kind, recorded by the seller of the programs.

films, including educational ones, audio recordings.

Read-only CDs are designated as follows: CD-ROM (translated as read-only memory)

For example, on this CD I recorded the archive of my site “Pensioner” for two years, just in case. At the same time, I deleted these files from my computer, since the site was developing, a lot was changing, and there was no point in storing all the files in the current working folder computer, taking up space. This CD can only be read and cannot be rewritten or added to other files. At the same time, you can copy files from the disk back to your computer if necessary.
This disc has a special layer that allows you to print on inkjet printer cover, disc label with inscriptions and pictures. This technology has since become obsolete. Technologies have now been developed with the help of which a cover, a label with inscriptions and pictures can be applied to a disc by simply turning it over in the drive to the other side. To do this, you need to buy a blank "LightScribe-enabled" CD if you know your drive supports this technology.

The easiest way, instead of making labels, is to write on the disk with a special felt-tip pen, which can be bought at a computer store.

CDs designed to be written once and read only have the letter “R” in their designation.
CD-R or DVD+R or DVD-R
and to write the letter "RW" multiple times:
DVD+RW
DVD CDs have larger volume than CDs and are more versatile. You can record any files, including audio and video, on such a universal disk. There are audio discs - Audio-CDs, intended only for listening in an audio player. This audio recording can also be played on a computer if it has installed program playback

Buying CDs for recording information, you need to keep in mind that they differ in recording speed and volume. It looks like this:

DVD + R is a disc for write-once only (including video) and read-only.
16x - recording speed - average
Disk capacity - 4.7 GB gigabytes
The box contains 25 empty discs (blanks)

CD-R is a disc for write-once only (including video) and read-only.
The disk capacity is 700 MB less, but the speed is higher - 52x, the number of disks in the box is 10 pcs.

DVD + RW - a disc for repeated recording, erasing, rewriting and reading.
Write speed from 1 to 4x
Disk capacity - 4.7 GB gigabytes

For writing or reading files to a CD it is inserted into the drive desktop computer or laptop. By pressing a button, the drive panel slides out, where the disk is neatly placed with the mirror side down.

By pressing the button again, the panel with the disk slides back.

If you need to transfer to external media large volume information, creating, for example, a music collection, a video library or a collection of paintings, they use external hard disks . They usually have small sizes and weight, large volume for storing information, high speed of writing and reading, and also durable. Saving a collection of files on a hard drive does not require physical space in the apartment.

While storing a collection on CDs requires special racks and space for them.

In addition, CDs are easily scratched, making the recorded files unreadable. The reliability of storing files on a hard drive is much higher. Information on an external hard drive can be repeatedly erased and rewritten and, of course, read.

There are different types of hard drives appearance and with various parameters.

They connect to the computer using a USB cable.

There are also external miniature devices for recording and storing information, which are called "flash memory" or "flash drive" or simply "flash drive". At the heart of this device is a microcircuit that can save information even when the power is turned off. Flash allows for repeated rewriting of information. Modern flash drives latest models The memory capacity even exceeds that of CDs.

Flash drives convenient due to their small size and ease of connection not only to a computer, but, for example, even to a TV. Modern digital TVs allow you to play movies recorded on a flash drive in some specific formats. The flash drive is inserted into the USB socket on the TV.

Plan

Introduction………………………………………………………………………………………...3

Storage media……………………………………………………………4

Encoding and reading information..……………………………………9

Development prospects…………………….…………………………………….15

Conclusion………………………………………………………………………………….18

Literature…………………………………………………………………………………19

Introduction

In 1945, John von Neumann (1903-1957), an American scientist, came up with the idea of ​​using external storage devices to store programs and data. Neumann developed a block diagram of a computer. All modern computers follow Neumann's scheme.

External memory is designed for long-term storage of programs and data. External memory devices (drives) are non-volatile; turning off the power does not lead to data loss. They can be built into the system unit or made in the form of independent units connected to the system unit through its ports. Based on the method of recording and reading, drives are divided, depending on the type of media, into magnetic, optical and magneto-optical.

Information coding is the process of forming a specific representation of information. A computer can only process information presented in numerical form. All other information (for example, sounds, images, instrument readings, etc.) must be converted into numerical form for processing on a computer. As a rule, all numbers in a computer are represented using zeros and ones (not ten digits, as is usual for people). In other words, computers usually operate in the binary number system, since this makes the devices for processing them much simpler.

Reading information– retrieving information stored in a storage device (memory) and transferring it to other devices of the computer. Reading information is performed when performing most machine operations, and sometimes is an independent operation.

During the abstract, we will consider the main types of information carriers, encoding and reading information, as well as development prospects.

Information carriers

Historically, the first storage media were punched tape and punched card input/output devices. Following them came external recording devices in the form of magnetic tapes, removable and permanent magnetic disks and magnetic drums.

Magnetic tapes are stored and used wound on reels. There were two types of coils: feeding and receiving. Tapes are supplied to users on feed reels and do not require additional rewinding when installing them in drives. The tape is wound onto a reel with the working layer inward. Magnetic tapes are classified as indirect access storage devices. This means that the search time for any record depends on its location on the media, since a physical record does not have its own address and in order to view it you need to view previous ones. Direct access storage devices include magnetic disks and magnetic drums. Their main feature is that the search time for any record does not depend on its location on the media. Each physical record on the medium has an address that allows direct access to it, bypassing other records. The next type of recording devices were packages of removable magnetic disks, consisting of six aluminum disks. The capacity of the entire package was 7.25 MB.

Let's take a closer look at modern storage media.

1. Flexible storage magnetic disks(NGMD – disk drive).

This device uses flexible magnetic disks as a storage medium - floppy disks, which can be 5 or 3 inches. A floppy disk is a magnetic disk, like a record, placed in an “envelope.” Depending on the size of the floppy disk, its capacity in bytes varies. If a standard 5'25" floppy disk can hold up to 720 KB of information, then a 3'5" floppy disk can hold 1.44 MB. Floppy disks are universal, suitable for any computer of the same class equipped with a disk drive, and can be used for storing, accumulating, distributing and processing information. The drive is a parallel access device, so all files are equally easily accessible. The disk is covered on top with a special magnetic layer, which ensures data storage. Information is recorded on both sides of the disk along tracks that are concentric circles. Each track is divided into sectors. The data recording density depends on the density of tracks on the surface, i.e., the number of tracks on the surface of the disk, as well as on the density of information recording along the track. The disadvantages include small capacity, which makes long-term storage of large amounts of information almost impossible, and the not very high reliability of the floppy disks themselves. Currently, floppy disks are practically not used.
2. Hard magnetic disk drive (HDD - hard drive)
It is a logical continuation of the development of magnetic information storage technology. Main advantages:
– large capacity;
– simplicity and reliability of use;
– the ability to access multiple files simultaneously;
– high speed access to data.
Among the shortcomings we can only highlight the lack removable media information, although external hard drives and backup systems are currently used.

The computer provides the ability, using a special system program, to conditionally split one disk into several. Such disks, which do not exist as a separate physical device, but represent only part of one physical disk, are called logical disks. Logical drives are assigned names using Latin letters [C:], , [E:], etc.

3. Compact disc reader (CD-ROM)

These devices use the principle of reading grooves on a metallized carrier layer of a compact disc with a focused laser beam. This principle makes it possible to achieve high density recording information, and, consequently, large capacity with minimal dimensions. A CD is an excellent means of storing information, it is cheap, practically not subject to any environmental influences, the information recorded on it will not be distorted or erased until the disk is physically destroyed, its capacity is 650 MB. It has only one drawback - the relatively small amount of information storage.
A) Differences between DVD and regular CD-ROM

The most basic difference is, naturally, the amount of information recorded. If you can burn 650 MB on a regular CD (although Lately There are discs of 800 MB, but not all drives will be able to read what is written on such a medium), then one DVD disc will fit from 4.7 to 17 GB. DVD uses a laser with a shorter wavelength, which has significantly increased the recording density, and in addition, DVD implies the possibility of two-layer recording of information, that is, on the surface of the compact there is one layer, on top of which another, translucent one is applied, and the first is read through the second in parallel . There are also more differences in the media themselves than seems at first glance. Due to the fact that the recording density has increased significantly and the wavelength has become shorter, the requirements for the protective layer have also changed - for DVD it is 0.6 mm versus 1.2 mm for regular CDs. Naturally, a disk of such thickness will be much more fragile compared to a classic blank. Therefore, another 0.6 mm is usually filled with plastic on both sides to get the same 1.2 mm. But the main bonus of such a protective layer is that, thanks to its small size, it became possible to record information on both sides on one compact, that is, to double its capacity, while leaving the dimensions almost the same.

B) DVD capacity

There are five types of DVDs:

1. DVD5 – single-layer, single-sided disc, 4.7 GB, or two hours of video;

2. DVD9 – double-layer single-sided disc, 8.5 GB, or four hours of video;

3. DVD10 – single-layer double-sided disc, 9.4 GB, or 4.5 hours of video;

4. DVD14 – double-sided disc, two layers on one side and one on the other side, 13.24 GB, or 6.5 hours of video;

5. DVD18 – double-layer, double-sided disc, 17 GB, or more than eight hours of video.

The most popular standards are DVD5 and DVD9.

IN) Possibilities

The situation with DVD media now resembles that of CDs, which for a long time also only stored music. Now you can find not only films, but also music (so-called DVD-Audio) and software collections, games, and films. Naturally, the main area of ​​use is film production.

G) Sound in DVD

Audio can be encoded in many formats. The most famous and frequently used are Dolby Prologic, DTS and Dolby Digital of all versions. That is, in fact, in the formats used in cinemas to obtain the most accurate and colorful sound picture.

D) Mechanical damage

TO mechanical damage CDs and DVDs are equally sensitive. That is, a scratch is a scratch. However, due to the much higher recording density, the losses on the DVD disc will be more significant. Now there are programs that can recover information even from damaged disks, though with the skipping of damaged sectors.

5. Portable USB drives

Fast-growing portable market hard drives, designed for transporting large amounts of data, attracted the attention of one of the largest hard drive manufacturers. Western Digital has announced the release of two device models called WD Passport Portable Drive. Options with a capacity of 40 and 80 GB are on sale. WD Passport Portable Drives are based on 2.5-inch WD Scorpio EIDE HDDs. They are packaged in a rugged case, equipped with support for Data Lifeguard technology, and do not require an additional power source (powered via USB). The manufacturer notes that the drives do not heat up, operate quietly and consume little energy.

6.USB Flash Drive

A new type of external storage medium for a computer, which appeared due to the widespread use of the USB (universal bus) interface and the advantages of microcircuits Flash memory. A sufficiently large capacity with a small size, energy independence, high speed of information transfer, protection from mechanical and electromagnetic influences, the ability to be used on any computer - all this allowed the USB Flash Drive to replace or successfully compete with all previously existing storage media.

What did the first man know? How to kill a mammoth, bison or catch a wild boar. In the Paleolithic era, there were enough cave walls to record everything that had been studied. The entire cave database would fit on a modest megabyte-sized flash drive. Over the 200,000 years of our existence, we have learned about the genome of the African frog, neural networks and we no longer draw on rocks. Now we have disks and cloud storage. As well as other types of storage media capable of storing the entire MSU library on one chipset.

What is a storage medium

A storage medium is a physical object whose properties and characteristics are used to record and store data. Examples of storage media are films, compact optical discs, cards, magnetic disks, paper and DNA. Storage media differ in the recording principle:

  • printed or chemical with paint: books, magazines, newspapers;
  • magnetic: HDD, floppy disks;
  • optical: CD, Blu-ray;
  • electronic: flash drives, solid state drives.

Data storages are classified according to signal shape:

  • analog, using a continuous signal for recording: audio compact cassettes and reels for tape recorders;
  • digital - with a discrete signal in the form of a sequence of numbers: floppy disks, flash drives.

The first storage media

The history of recording and storing data began 40 thousand years ago, when Homo sapiens came up with the idea of ​​making sketches on the walls of their homes. The first cave art is found in the Chauvet Cave in the south of modern France. The gallery contains 435 drawings depicting lions, rhinoceroses and other representatives of the late Paleolithic fauna.

To replace the Aurignacian culture in the Bronze Age arose fundamentally the new kind information carriers - tuppum. The device was a clay plate and resembled a modern tablet. Records were made on the surface using a reed stick - a stylus. To prevent the work from being washed away by the rain, the tuppums were burned. All tablets with ancient documentation were carefully sorted and stored in special wooden boxes.

The British Museum has a tuppum containing information about a financial transaction that took place in Mesopotamia during the reign of King Assurbanipal. An officer from the prince's retinue confirmed the sale of the slave Arbela. The tablet contains his personal seal and notes on the progress of the operation.

Kipu and papyrus

From the 3rd millennium BC, papyrus began to be used in Egypt. Data is recorded on sheets made from the stems of the papyrus plant. The portable and lightweight form of storage media quickly replaced its clay predecessor. Not only the Egyptians, but also the Greeks, Romans, and Byzantines wrote on papyrus. In Europe, the material was used until the 12th century. Last document, written on papyrus, is a papal decree of 1057.

At the same time as the ancient Egyptians, on the opposite end of the planet, the Incas invented the kippa, or “talking knots.” Information was recorded by tying knots on spinning threads. Kipu kept data on tax collections and population. Presumably, non-numeric information was used, but scientists have yet to unravel it.

Paper and punch cards

From the 12th century to the mid-20th century, paper was the main storage medium for data. It was used to create printed and handwritten publications, books, and media. In 1808, punched cards began to be made from cardboard - the first digital media information. They were sheets of cardboard with holes made in a certain sequence. Unlike books and newspapers, punch cards were read by machines rather than by people.

The invention belongs to an American engineer with German roots, Herman Hollerith. The author first used his brainchild to compile mortality and birth rate statistics at the New York Board of Health. After trial attempts, punched cards were used for the US Census in 1890.

But the idea of ​​making holes in paper to record information was far from new. Back in 1800, punched cards were introduced into use by the Frenchman Joseph-Marie Jacquard to control a weaving loom. Therefore, the technological breakthrough consisted in Hollerith’s creation not of punched cards, but of a tabulation machine. This was the first step towards automatic reading and calculation of information. Herman Hollerith's TMC tabulating machine company was renamed IBM in 1924.

OMR cards

They are sheets of thick paper with information recorded by humans in the form of optical marks. The scanner recognizes the marks and processes the data. OMR cards are used to create questionnaires, multiple choice tests, bulletins, and forms that must be completed manually.

The technology is based on the principle of drawing up punched cards. But the machine does not read through holes, but bulges, or optical marks. The calculation error is less than 1%, so OMR technology continues to be used government agencies, examination authorities, lotteries and bookmakers.

Punched tape

A digital storage medium in the form of a long strip of paper with holes. Perforated tapes were first used by Basile Bouchon in 1725 to control the weaving loom and mechanize the selection of threads. But the tapes were very fragile, easily torn and at the same time expensive. Therefore, they were replaced with punched cards.

Since the end of the 19th century, punched paper tape has been widely used in telegraphy, for data entry into computers in the 1950s and 1960s, and as media for minicomputers and CNC machines. Now reels with wound punched paper tape have become an anachronism and have sunk into oblivion. Paper media has been replaced by more powerful and voluminous data storage facilities.

Magnetic tape

The debut of magnetic tape as a computer storage medium took place in 1952 for the UNIVAC I machine. But the technology itself appeared much earlier. In 1894, Danish engineer Woldemar Poulsen discovered the principle of magnetic recording while working as a mechanic for the Copenhagen Telegraph Company. In 1898, the scientist embodied the idea in a device called the “telegraph”.

A steel wire passed between the two poles of an electromagnet. The recording of information on the medium was carried out through uneven magnetization of oscillations of the electrical signal. Waldemar Poulsen patented his invention. At the 1900 World Exhibition in Paris, he had the honor of recording the voice of Emperor Franz Joseph on his device. The exhibit with the first magnetic sound recording is still kept in the Danish Museum of Science and Technology.

When Poulsen's patent expired, Germany began improving magnetic recording. In 1930, steel wire was replaced by flexible tape. The decision to use magnetic stripes belongs to the Austrian-German developer Fritz Pfleimer. The engineer came up with the idea of ​​coating thin paper with iron oxide powder and recording through magnetization. Compact cassettes, video cassettes and modern storage media for personal computers were created using magnetic film.

HDDs

Winchester, HDD or HDD- This hardware device With non-volatile memory, which means complete preservation of information, even when the power is turned off. It is a secondary storage device consisting of one or more plates onto which data is written using a magnetic head. HDDs are located inside the system unit in the drive bay. Connect to motherboard using an ATA, SCSI or SATA cable and to the power supply.

The first hard drive was developed by the American company IBM in 1956. The technology was used as a new type of storage media for the commercial computer IBM 350 RAMAC. The abbreviation stands for “method of random access to accounting and control.”

To accommodate the device in your home, you would need a whole room. Inside the disk were 50 aluminum plates, 61 cm in diameter and 2.5 cm wide. The size of the data storage system was equivalent to two refrigerators. His weight was 900 kg. The RAMAC capacity was only 5MB. A funny number for today. But 60 years ago it was regarded as technology tomorrow. After the announcement of the development, the daily newspaper of the city of San Jose released a report entitled “A machine with super memory!”

Dimensions and capabilities of modern HDDs

HDD - computer media information. Used to store data including images, music, videos, text documents and any materials created or uploaded. In addition, they contain files for operating system and software.

The first hard drives could hold up to several tens of MB. Constantly developing technology allows modern HDDs to store terabytes of information. This is about 400 films with medium resolution, 80,000 songs in mp3 format or 70 computer role playing games, similar to Skyrim, on one device.

Diskette

Floppy, or flexible magnetic disk, is a storage medium created by IBM in 1967 as an alternative to HDD. Floppy disks were cheaper than hard drives and were intended for storing electronic data. Early computers did not have CD-ROM or USB. Floppy disks were the only way installations new program or backup.

The capacity of each 3.5-inch floppy disk was up to 1.44 MB, when one program “weighed” at least one and a half megabytes. That's why Windows version 95 appeared on 13 DMF floppies at once. The 2.88 MB floppy disk appeared only in 1987. This electronic storage medium existed until 2011. Modern computers do not have floppy drives.

Optical media

With the advent of the quantum generator, the popularization of optical storage devices began. Recording is carried out by a laser, and data is read using optical radiation. Examples of storage media:

  • Blu-ray discs;
  • CD-ROM drives;
  • DVD-R, DVD+R, DVD-RW and DVD+RW.

The device is a disk covered with a layer of polycarbonate. There are micro-grooves on the surface that are read by a laser when scanning. The first commercial laser disc appeared on the market in 1978, and in 1982 the Japanese SONY company and Philips released CDs. Their diameter was 12 cm, and the resolution was increased to 16 bits.

Electronic storage media in CD format were used exclusively for reproduction sound recording. But at that time it was advanced technology, for which Royal Philips Electronics received an IEEE award in 2009. And in January 2015, the CD was awarded as the most valuable innovation.

In 1995, Digital Versatile Discs, or DVDs, became optical media new generation. A different type of technology was used to create them. Instead of red, the DVD laser uses shorter infrared light, which increases the storage capacity of the storage medium. Dual-layer DVDs can store up to 8.5 GB of data.

Flash memory

Flash memory is integrated circuit, which does not require constant power to store data. In other words, it is non-volatile semiconductor computer memory. Storage devices with flash memory are gradually conquering the market, displacing magnetic media.

Advantages of Flash technology:

  • compactness and mobility;
  • large volume;
  • high speed;
  • low power consumption.

Flash-type storage devices include:

  • USB flash drives. This is the simplest and cheapest storage medium. Used for repeated recording, storage and transmission of data. Sizes range from 2 GB to 1 TB. Contains a memory chip in a plastic or aluminum case with a USB connector.
  • Memory cards. Designed for storing data on phones, tablets, digital cameras and other electronic devices. They differ in size, compatibility and volume.
  • SSD. Solid state drive with non-volatile memory. This is an alternative to a standard hard drive. But unlike hard drives, SSDs do not have a moving magnetic head. Due to this they provide fast access to data, do not make squeaks like HDDs. The disadvantage is the high price.

Cloud storage

Cloud online storage is a modern storage medium that is a network of powerful servers. All information is stored remotely. Each user can access data at any time and from anywhere in the world. The disadvantage is complete dependence on the Internet. If you do not have a network connection or Wi-Fi, access to data is blocked.

Cloud storage is much cheaper than its physical counterparts and has a larger volume. The technology is actively used in corporate and educational environments, development and design of web applications for computer software. You can store any files, programs, backups, use them as a development environment.

Of all the listed types of storage media, the most promising are cloud storage. Also, more and more PC users are switching from magnetic hard drives to solid-state drives and flash memory media. Development of holographic technologies and artificial intelligence promises the emergence of fundamentally new devices that will leave flash drives, SDDs and disks far behind.




Flexible magnetic disks (floppy disks). A floppy drive is fundamentally similar to a disk drive. hard drives. Rotational speed floppy disk about 10 times slower, and the heads touch the surface of the disk. Basically, the structure of information on a floppy disk, both physical and logical, is the same as on a hard disk. In terms of logical structure, the floppy disk does not have a disk partition table.


The principle of operation of a floppy disk. A floppy disk drive (floppy disk, or simply floppy disk) has two motors: one ensures a stable rotation speed of the floppy disk inserted into the drive, and the second moves the read-write heads. The rotation speed of the first motor depends on the type of floppy disk and ranges from 300 to 360 rpm. The motor for moving the heads in these drives is always stepper. With its help, the heads move along a radius from the edge of the disk to its center at discrete intervals. Unlike the hard drive head drive in this device do not “hover” above the surface of the floppy disk, but touch it.


Optical (laser) disk. First optical laser discs appeared in 1972 and demonstrated great capabilities for storing information. The volumes of information stored on them made it possible to use them to store huge amounts of data (such as databases, encyclopedias, collections of video and audio data). Easy replacement of these disks made it possible to “carry with you” all the materials required for work, in any volume. Optical disks had very high reliability and durability, which made it possible to use them for archival information storage.


The principle of operation of the disk. The operating principle of the drive resembles the operating principle of conventional drives for floppy disks. Surface optical disk(CD-ROM) moves relative to the laser head at a constant linear speed, and angular velocity varies depending on the radial position of the head. The laser beam is directed onto the track and focused using a coil. The beam penetrates through protective layer plastic and falls on the reflective layer of aluminum on the surface of the disk. When it hits the protrusion, it is reflected onto the detector and passes through a prism, which deflects it onto a light-sensitive diode. If the beam hits the hole, it is scattered and only a small part of the radiation is reflected back and reaches the photosensitive diode. On the diode, light pulses are converted into electrical ones, bright radiation is converted into zeros, and weak radiation into ones. Thus, the pits are perceived by the drive as logical zeros, and the smooth surface as logical ones


Hard magnetic disk (hard drive). A hard disk drive or hard drive is the most widely used storage device. large capacity, in which the information carriers are round aluminum plotter plates, both surfaces of which are coated with a layer of magnetic material. Used for permanent storage of program information and data.


The operating principle of a hard drive. The surface of the plotter has a magnetic coating only 1.1 microns thick, as well as a layer of lubricant to protect the head from damage when lowering and raising on the go. When the plotter rotates, an air layer is formed above it, which provides an air cushion for the head to hover at a height of 0.5 microns above the surface of the disk. Winchester drives have a very large capacity: from hundreds of megabytes to tens of GB. U modern models spindle rotation speed reaches 7200 rpm, average data search time is 10 ms, maximum speed data transfer up to 40 MB/s. Unlike a floppy disk, a hard drive rotates continuously. The hard drive is connected to the processor via a controller hard drive. All modern drives are equipped with a built-in cache (64 KB or more), which significantly increases their performance.


Advantages and disadvantages. Carriers.Advantages.Disadvantages. Floppy disk Compact, low price. Low speed of information exchange, small amount of memory, Disk durable, easy to use. Information is not sufficiently protected, fragile. Hard drive The capacity of memory is significantly higher than that of flexible ones; the speed of information exchange is much greater. Non-mobile.









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