Known media. Material media and their development

Electronic storage media

The technology of recording information on magnetic media appeared relatively recently - approximately in the middle of the 20th century (40s - 50s). But several decades later - in the 60s - 70s - this technology became very widespread throughout the world.

Magnetic tape consists of a strip of dense material onto which a layer of ferromagnetic materials is sprayed. It is on this layer that information is “remembered”. The recording process is also similar to the process of recording on vinyl records - using a magnetic induction coil, instead of a special apparatus, a current is supplied to the head, which drives the magnet. Sound recording on film occurs due to the action of an electromagnet on the film. The magnetic field of the magnet changes in time with sound vibrations, and thanks to this, small magnetic particles (domains) begin to change their location on the surface of the film in a certain order, depending on the effect on them of the magnetic field created by the electromagnet. And when playing a recording, the reverse recording process is observed: the magnetized tape excites in the magnetic head electrical signals, which, after amplification, are fed further into the speaker.

Compact cassette (audio cassette or simply cassette) is an information carrier on magnetic tape; in the second half of the 20th century, it was a common media carrier for sound recording. Used to record digital and audio information. The compact cassette was first introduced in 1964 by Philips. Due to its relative cheapness for a long time(from the early 1970s to the 1990s) the compact cassette was the most popular recorded audio medium, however, starting in the 1990s,

was supplanted by compact discs.

Now there are many in the world various types magnetic media: floppy disks for computers, audio and video cassettes, reel-to-reel tapes, etc. But new laws of physics are gradually being discovered, and with them new possibilities for recording information. Just a couple of decades ago, many information carriers appeared based on new technology - reading information using lenses and a laser beam.

The development of material carriers of documented information generally follows the path of a continuous search for objects with high durability, large information capacity with minimal physical dimensions of the medium. Since the 1980s, optical (laser) disks have become increasingly widespread. These are plastic or aluminum disks designed to record and reproduce information using a laser beam.

Based on application technology, optical, magneto-optical and digital CDs are divided into 3 main classes:

1. Discs that allow single recording and repeated playback of signals without the possibility of erasing them (CD-R; CD-WORM - Write-Once, Read-Many - recorded once, counted many times). Used in electronic archives and data banks, in external computer storage devices.

2. Reversible optical discs, allowing you to repeatedly record, play and erase signals (CD-RW, CD-E). These are the most versatile disks, capable of replacing magnetic media in almost all applications.

3. Digital universal video discs DVD (Digital Versatile Disk) such as DVD-ROM, DVD-RAM, DVD-R with large capacity(up to 17 GB).

The name of optical discs is determined by the method of recording and reading information. The information on the track is created by a powerful laser beam that burns depressions on the mirror surface of the disk, and is an alternation of depressions and reflective areas. When reading information, the mirror islands reflect the light of the laser beam and are perceived as one (1), the depressions do not reflect the beam and, accordingly, are perceived as zero (0). This principle makes it possible to achieve high density recording information, and therefore large capacity with minimal dimensions. A CD is an ideal means of storing information - it is ridiculously 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, and has a capacity of 700 MB.

Magneto-optical disk is an information carrier that combines the properties of optical and magnetic storage devices. The disk is made using ferromagnets. Magneto-optical disks, for all their advantages, have serious drawbacks: relatively low write speed, caused by the need to erase the contents of the disk before writing, and after writing - a read test; high energy consumption - to heat the surface, lasers of significant power are required, and therefore high energy consumption. This makes it difficult to use MO burner drives in mobile devices.

DVD (Digital Versatile Disc - digital multi-purpose disk) is a disk-shaped information carrier that is similar in appearance to a CD, but has the ability to store a larger amount of information due to the use of a laser with a shorter wavelength, than for regular CDs. The first discs and DVD players appeared in November 1996 in Japan and March 1997 in the USA. They were intended for recording and storing video images. It’s interesting that the first 3.95 GB DVD discs cost $50 apiece back then. Currently, there are six varieties of such disks with capacities from 4.7 to 17.1 GB. They are used to record and store any information: video, audio, data.

Working with information in our time is unthinkable without a computer, since it was originally created as a means of information processing and only now it began to perform many other functions: storage, transformation, creation and exchange of information. But before it took on its now familiar form, the computer underwent three revolutions.

The first computer revolution has come to an end

50s; its essence can be described in two words: computers appeared.

They were invented no less than ten years earlier, but it was at that time that serial machines began to be produced; these machines ceased to be an object of research for scientists and a curiosity for everyone else. A decade and a half later, no large organization could afford to do without a computer center. If you talked about a computer back then, you immediately imagined machine rooms filled with racks, in which people in white coats were thinking intently. And then the second revolution took place. Almost simultaneously, several companies discovered that the development of technology had reached a level where it was not necessary to build computer center, and he himself became small. These were the first minicomputers. But another ten years passed, and the third revolution arrived - in the late 70s, personal computers appeared. In a short time, having gone from a desktop calculator to a full-fledged small machine, PCs took their place on the desktops of individual users.

At the very moment when the first computer processed a few bytes of data for the first time, the question immediately arose: where and how to store the results obtained? How to save calculation results, text and graphic images, arbitrary data sets?

First of all, there must be a device with which the computer will store information, then a storage medium is required on which it can be transferred from place to place, and another computer must also easily read this information. Let's take a look at some of these devices.

1. Punched card reader: designed for storing programs and data sets using punched cards - cardboard cards with holes punched in a certain sequence. Punch cards were invented long before the advent of the computer; with their help, very complex and beautiful fabrics were produced on looms, because they controlled the operation of the mechanism. Change the set of punched cards and the fabric pattern will be completely different - it depends on the location of the holes on the card. In relation to computers, the same principle was used, only instead of a pattern of fabric, holes were given commands to the computer or sets of data. This method of storing information is not without its disadvantages: - very low speed access to information; - a large volume of punched cards for storing a small amount of information; - low reliability of information storage; - in addition, small circles of cardboard were constantly flying from the puncher, which fell on their hands, in their pockets, got stuck in their hair, and the cleaning ladies were terribly unhappy. People were forced to use punch cards not because they particularly liked this method, or because it had some undeniable advantages, no, it had no advantages at all, it’s just that at that time there was nothing else, there was nothing to choose from , I had to get out.

2. Magnetic tape drive (streamer): based on the use of a tape-type device and cassettes with magnetic film. This method of storing information has been known for a long time and is successfully used today. This is explained by the fact that a fairly large amount of information can be placed on a small cassette; the information can be stored for a long time and its access speed is much higher than that of a punch card reader. On the other hand, the streamer is only suitable for accumulating, storing large amounts of information, and backing up data. It is almost impossible to process information using a streamer: a streamer is a sequential data access device: to get the 5th file we must scroll through four. What if you need a 7529?

3. 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 a cardboard 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 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.

4. Hard magnetic disk drive (HDD - hard drive): is a logical continuation of the development of magnetic information storage technology. They have very important advantages: - extremely large capacity; - simplicity and reliability of use; - the ability to access thousands of files simultaneously; - high speed data access.

5. CDs and DVDs we have already reviewed.

But since the flow of information is only increasing, it is necessary to develop more and more new means and devices for its creation, processing, storage and transmission.

We have already discussed above storing data on CDs and DVDs. Despite their convenience, due to the need to use the largest possible amount of information, the process of replacing them is already beginning. In the coming years, flash memory will be a formidable competitor to hard drives in personal computing devices such as computers.

6. Flash memory is a type of solid-state semiconductor non-volatile rewritable memory.

Due to its compactness, low cost and low power requirements, flash memory is already widely used in portable devices operating on batteries and accumulators - digital cameras and video cameras, digital voice recorders, MP3 players, PDAs, mobile phones, as well as smartphones. In addition, it is used to store built-in software in various peripheral devices (routers, PBXs, communicators, printers, scanners). It does not contain moving parts, so, unlike hard drives, it is more reliable and compact.

The main weak point of flash memory is the number of rewrite cycles. It can be read as many times as desired, but it can only be written to such memory a limited number of times (usually about 10 thousand times). Despite the fact that there is such a limitation, 10 thousand rewrite cycles is much more than a floppy disk or CD can withstand. Flash memory is best known for its use in USB flash drives. flash drive). Thanks to their high speed, capacity and compact size, USB flash drives are already displacing CDs from the market.

Goals and objectives:

• Search for information.

• Find out the principle of operation and the amount of information of a floppy disk, disk, hard drive.

• Identify advantages and disadvantages.

Types of media.

• A medium is a material object capable of storing information.

• The storage media in the external memory of modern computers are magnetic or optical (laser) disks, magnetic tapes and some others.

Flexible magnetic disks (floppy disks).

A floppy drive is fundamentally similar to a hard drive. The rotation speed of a floppy disk is 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.

The 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 is similar to that of conventional floppy disk drives. The surface of the optical disk (CD-ROM) moves relative to the laser head constant linear speed, and the angular velocity changes depending on the radial position of the head. The laser beam is directed onto the track and focused using a coil. The beam penetrates the protective layer of plastic and hits 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).

• Hard disk drive or hard drive- this is the most widespread high-capacity storage device, in which the information carriers are round aluminum plates - plotters, both surfaces of which are covered with a layer of magnetic material. Used for permanent storage of information - programs and data.

The operating principle of a hard drive.

• The plotter surface has magnetic coating only 1.1 microns thick and layer of lubricant to protect the head from damage when lowering and lifting while moving. When the plotter rotates, a air layer, which provides air cushion for the head to hang at a height of 0.5 microns above the disk surface.

• Winchester drives have very large capacity: from hundreds of megabytes to tens of GB. In modern models, the spindle speed reaches 7200 rpm, the average data search time is 10 ms, and the maximum data transfer speed is up to 40 MB/s.

• Unlike a floppy disk, a hard drive rotates continuously.

• The hard drive is connected to the processor via hard drive controller.

• All modern drives are equipped built-in cache(64 KB or more), which significantly improves their performance.

Advantages and disadvantages.

Conclusion.

• Having considered all the main types of external media, we came to the conclusion that they are all good to use. However, in everyday life I would choose a disk, because it is more common, easier to use, and more durable than other types of media.

An electronic storage medium is a device for storing, accumulating and transmitting information. In a personal computer, it is used for this purpose. internal storage device called a 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 uses additional external devices to store information.

Common external media information 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 is inserted into the optical drive of the computer to be burned. 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 one. working folder computer, taking up space. This CD can only be read, it cannot be overwritten or other files can be added. 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 a cover and disc label with inscriptions and pictures on an inkjet printer. 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 once 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 a larger storage capacity 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 it is necessary to transfer a large amount of information to an external medium, creating, for example, a music collection, a video library or a collection of paintings, use external hard drives. They are usually small in size and weight, have a large capacity for storing information, high speed writes and reads, and is 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 erased and rewritten many times and, of course, read.

Hard drives come in different appearances and with different 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.

External storage media

In this section I will talk about external storage media. Let me remind you that they come last in the memory hierarchy. They can record the most data. Such drives are not so convenient (for example, the user is often too lazy to change the CD), but they are very cheap.

External media is not just disks or floppy disks. These also include external hard drives, optical drives, USB flash cards, etc.

External hard disk

External hard drives have been around for a long time. In structure they are almost no different from the internal ones. We can say that these are the most regular hard drives, but supplied not with the computer (in particular, with a laptop), but in a special plastic case.

In addition to the hard drive, there is a special chip located there that converts signals for transmission through one of the connectors on a laptop or desktop PC). You connect the small box with a cable to the computer, and after a few seconds the operating system detects the new hard drive(Fig. 4.11). You don't even have to reboot it.

Rice. 4.11. External hard drive 2.5" format

Today two methods are used connecting hard disk: via USB and FireWire. The first type has been discussed more than once. Its purpose is universal, so not only a mouse, keyboard, printer, scanner, but also some external media are compatible with it.

Some time ago, FireWire (also known as IEEE 1394 and i.Link) was only available to owners of professional and expensive computers, but now almost every laptop has it. Formally, FireWire is preferable for connecting an external hard drive. Due to better security, it will be able to provide greater reliability and data transfer speed. However, external hard drives There are very few devices on the market that support the IEEE 1394 format. Most often they are compatible with USB 2.0.

There is a way to turn a regular internal hard drive into an external one. Computer stores have a good selection of external hard drive cases. You need to purchase a case and a hard drive for it. Then, according to the instructions, insert the hard drive inside - and you're done.

It is important to follow several rules. In the previous chapter, I said that there are several sizes of hard drives, the most common being 3.5 and 2.5”. The former are used in desktop computers, the latter in mobile computers. Please note that a case may only be compatible with one of them.

You should pay attention to the connection interface. This can be Serial ATA (or SATA) and IDE (or UDMA, Ultra ATA). It is necessary that both the hard drive and the case support the same connection method. Otherwise nothing will work.

External optical drive

Today, laptop manufacturers are trying to equip each model with an optical drive for working with CDs. In the case of miniature subnotebooks, this cannot be done for obvious reasons. However, if you need to work with disks, then purchasing an external optical drive is the way out.

As is the case with hard drives, external drives are most often internal versions enclosed in a case. They happen different sizes. The largest and heaviest are analogues of drives installed in desktop computers. You probably shouldn't buy them. Firstly, these drives are quite bulky, and secondly, an additional socket may be required for operation, which is not in favor of mobility.

If desired, you can also find a “laptop” external drive. It will be much more compact and, of course, more expensive. If you need special version for transportation, then this option will be one of the best. “One of” because there are models designed specifically to be carried with a laptop (Fig. 4.12).

Rice. 4.12. Special drive designed to be carried with a laptop

Such optical drives are not based on internal analogues, which negatively affects their cost. But the ease of transportation is excellent.

As for the connection method, it is almost always USB 2.0. Sometimes FireWire is added to it, but there are not many such models.

There is another type of external media - USB flash drives (Fig. 4.13), which we have already discussed more than once. This type of media may be most convenient for you.

Rice. 4.13. USB flash drive

Chapter 1 Optical storage media Structure of CD. DVD structure. Rules for using CDs. CD/DVD drive. In the late 1970s, Sony and Philips began jointly developing a unified standard for optical storage media. Philips created a laser