Examples of external information media. Modern media. Data Structure on Disk
In modern society, three main types of information carriers can be distinguished:
1) paper;
2) magnetic;
3) optical.
Modern memory microcircuits allow you to store 1 cm 3 to 10 10 bits of information, but it is 100 billion times less than in DNA. It can be said that modern technology is significantly losing biological evolution.
However, if you compare the information capacity of traditional media (books) and modern computer carriers, then progress is obvious:
A4 sheet with text (applied on a computer of the 12th bow with single interval) - about 3,500 characters
Tutorial page - 2000 characters
Flexible magnetic disk - 1.44 MB
Optical CD-R (W) - 700 MB
Optic dVD disk - 4.2 GB
Flash drive - several GB
Removable hDD or hard magnetic disk-hundred GB
Thus, 2-3 books can be stored on a diskette, and a whole library, which includes tens of thousands of books on a hard magnetic disk or DVD.
Advantages and disadvantages of storage of information in the internal and external memory. (The dignity of the internal memory is the speed-reproduction of information, and the disadvantage of the information is forgotten. The dignity of the external memory is large amounts of information is stored for a long time, and the disadvantage of access to certain information is required (for example, to prepare an abstract on the subject it is necessary to find, analyze and analyze choose suitable material))
Archive of information
One of the most widespread types of service programs are programs designed to archive, packaging files by compressing the information stored in them.
Compress information - This is the process of converting information stored in the file, to the form at which redundancy is reduced in its representation and, accordingly, a smaller storage memory is required.
Compressing information in files is made by eliminating redundancy different ways, for example, by simplifying codes, exclude constant bits or representing repeating symbols or a repeated sequence of symbols as a repetition coefficient and corresponding characters. Various algorithms for such compression of information are applied.
It can be compressed as one and several files that are placed in a compressed form in the so-called archive file or archive.
Archive file. - This is a specially organized file containing one or more files in a compressed or uncompressed form and service information on file names, date and time of their creation or modification, sizes, etc.
The purpose of file packaging is usually ensuring more compact placement of information on disk, reducing time and, accordingly, the cost of transmitting information on communication channels in computer networks. In addition, the packaging in one archive file file file significantly simplifies their transfer from one computer to another, reduces the time to copy files to discs, allows you to protect information from unauthorized access, promotes protection from infection with computer viruses.
The degree of compression depends on the program used, the compression method and the type of source file. Graphic image files, text files and data files are most compressed, for which the compression ratio can reach 5-40%, the files of executable programs and loading modules are smaller, less compressing. Archival files almost do not compress. Programs for archiving are distinguished by the compression methods used, which respectively affects the degree of compression.
Archiving (Packaging) - Room (loading) of source files to the archive file in a compressed or uncompressed form. Unzipping (unpacking) - the process of restoring files from the archive exactly in this form, which they had before downloading to the archive. When unpacking, the files are retrieved from the archive and placed on the disk or in rAM;
Programs that perform packaging and unpacking files are called archival programs .
Large in volume Archival files can be placed on multiple disks (volumes). Such archives are called multi-volume. Tom is an integral part of a multi-volume archive. Creating an archive from several parts, you can record it parts into several floppy disks.
The main characteristics of archival program are:
work speed;
service (set of archiver functions);
the degree of compression is the ratio of the size of the source file to the size of the packed file.
The main functions of the archivers are:
· Creating archive files from individual (or all) files of the current directory and its subdirectories by downloading into one archive to 32,000 files;
· Add files to archive;
· Removing and deleting files from the archive;
· View archive contents;
· View the contents of archived files and search for strings in archived files;
· Enter the Comments to the files;
· Creating multi-volume archives;
· Creation of self-extracting archives, both in one volume and in the form of several volumes;
· Ensuring information security in the archive and access to files placed in the archive, protection of each of the files placed in the file archive cyclic code;
· Testing of the archive, checking the security in it;
· Restore files (partially or completely) from damaged archives;
· Support types of archives created by other archivers and others.
Information carriers - Material that is intended for recording, storing and subsequent information reproduction.
Media information - strictly defined part of a specific information systemserving for intermediate storage or information transfer.
Media information - This is a physical environment in which it is fixed.
Paper, film, brain cells, cardiac cards, punctuents, magnetic ribbons and disks or cells of the computer can be played as a carrier. Modern technique offers all new and new varieties of media. To encode information, they use electrical, magnetic and optical properties of materials. Media are developed in which the information is fixed even at the level of individual molecules.
In modern society, three main types of information carriers can be distinguished:
1) Perforation - have a paper base, information is entered in the form of punching in the appropriate line and column. The amount of information is 800 bits or 100 KB;
2) Magnetic - flexible magnetic discs and cassette magnetic tapes are used as them;
3) optical.
For information carriers include:
Magnetic discs;
- magnetic drums - Early variety computer memorywidespread in 1950-1960. Invented by the Gustav of Tazeška in 1932 in Austria. In the future, the magnetic drum was supplanted by memory on magnetic cores.
- diets - Portable magnetic information media used for multiple recording and storage of data relatively small volume. Recording and reading is carried out using a special disk drive;
- magnetic ribbons - carrier of the magnetic record, which is a thin flexible tape consisting of the base and the magnetic working layer;
- optical disks - a carrier of information in the form of a disc with a hole in the center, the information from which is read with a laser. Initially, the CD was created for digital storage of audio, but is currently widely used as a wide-purpose storage device;
- flash memory - A variety 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). Erasing occurs in areas, so one bit or byte cannot be changed without overwriting the entire site.
All media can be divided into:
1. Personalizing (documents).
2. Machine-readable (machines) - for intermediate storage of information (discs).
3. Human farms - combined carriers of narrow specialty (forms with magnetic stripes).
However, the rapid development of funds computer equipment Erased the line between the 1st and 3rd group - a scanner appeared, which allows you to enter information from documents in memory of the computer.
All currently available media can be divided by various features. First of all, it should be distinguished energy dependent and non-volatile Drive drives.
Non-volatile drives used for archiving and saving data arrays subdivided:
1. By type of recording:
– magnetic drives (hard disk, flexible disk, shift disc);
- magnetic and optical systems, also called MO;
- optical, such as CD (Compact Disk, Read Only Memory) or DVD (Digital Versatile Disk);
2. According to the methods of construction:
- rotating plate or disk (like hard disk, flexible disk, interchangeable disk, CD, DVD or Mo);
- ribbon carriers of various formats;
- Drives without moving parts (for example, Flash Card, Ram (Random Access Memory), having a limited scope due to relatively small amounts of memory compared to the above).
If you want to fast access For information, such as, for example, when displaying or transmitting data, media with a rotating disk are used. For archiving performed periodically (backup), on the contrary, tape carriers are more preferred. They have large amounts of memory in combination with a low price, however, with relatively low speed.
For the purpose of information media differ in three groups:
1. spread of information: Media with pre-recorded information, such as CD ROM or DVD-ROM;
2. archiving: media for one-time recording of information, such as CD-R or DVD-R (R (RECORD ABLE) - for recording);
3. reservation (Backup) or data transmission: Media with the ability to multiple information records, such as floppy disks, hard disk, Mo, CD-RW (RW (Rewritable) - rewritable and tapes.
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;
- in terms of the economy and efficiency of the provision of relevant (intended for short-term storage) of 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.
Drives optical disks They are divided into three types:
- without recording options - CD-ROM and DVD-ROM (ROM - Read Only Memory, read-only memory). On the cD-ROM disks And the DVD-ROM stores information that was recorded on them in the manufacturing process. Record on them new information impossible;
- 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, CD drives are marked with three numbers "reading speed x speed records CD-R x CD-RW recording speed "(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 |
Human civilization during its existence found many ways to record information. Every year, its volumes grow in for this reason, carriers are changing. It is about this evolution that will be discussed below.
Vestiges of the past
The ancient monuments of human activity can be considered the rock paintings, which were depicted animals that were for the goals of hunting. The first material carriers of information were natural.
This breakthrough can be considered the appearance of writing from the Sumerians who lived in modern Iraq and used not a stone, but clay plates that were burned after the letter. Thus, their conservation increased significantly. However, the speed with which knowledge was recorded was extremely small.
You can also note the Egyptian papyrus, wax, skins, on which for the first time began to write in Persia. In Asia used bamboo and silk. The ancient Indians had a unique system of a nodule letter. In Russia, there was a berson, which archaeologists find today.
Paper
Paper media made a coup, the scale of which is difficult to overestimate. Despite the fact that the first analogs of cellulose material were obtained by the Chinese in the second century, it became publicly available only in the XIX century.
With paper connected and appearance of books. In the 1450s, the German inventor invented a manual typographic machine, with the help of which two copies of the Bible published. These events served as a point of reference for a new era of mass typography. It was thanks to him that he stopped being a lot of thin layer of mankind, and became accessible to everyone.
Today's paper is newspaper, offset, coated, etc. Its choice depends on specific purposes. And although the white canvas is in demand as ever, its innovative position has already lost.
Perfocards and punctants
The next impetus in its development information carriers received at the beginning of the XIX century, when the first cardboard perfocards appeared. In certain places there were holes with which data was read. Initially, the technology was used to manage
Interest in the novelty increased after it began to use it in the US for a more convenient and rapid counting of the results of the country's population in 1890. The company's production was engaged in the company IBM in the future, which became a pioneer of computer technologies. The flowering technology fell on the middle of the XX century. It was then that I began to spread the systematic and summarizing a variety of data.
The first machine carriers were also punched. They were produced from paper and were used in telegraphs. Due to its ribbon format, it is easy to make input and output. This made them indispensable until the emergence of magnetic competitors.
Magnetic tape
No matter how good former external information carriers were good, they could not reproduce what was fixed. This problem It was solved with the advent of the magnetic tape. It was a flexible base covered by several layers on which information is recorded. As working environment Various chemical elements were performed: iron, cobalt, chrome.
Magnetic information media made jerk recording. It was this innovation that allowed new technology Quickly fit in Germany in the 30s. Former devices (phonographs, gramophones, patefones) were characterized by mechanical character and were not practical. The tape recorder of the coil and cassette type was obtained.
In the 50s, attempts were made to use development data as computer media. Magnetic tapes were introduced into personal computers in the 80s. Their popularity as a whole was explained by such advantages. As a large capacity, comparative cheap production and low power consumption.
The lack of ribbons can be considered the shelf life. Over time, they are demagned. At best, the data is saved for 40-50 years. However, it did not prevent the format to become popular all over the world. Separately, it is worth mentioning the videotapes, the flourishing of which came to the end of the XX century. Magnetic information media became the basis of the body and the broadcasting of a new type.
Hard drives
In the meantime, the development of the industry continued. Large-volume information carriers required upgrades. The first hard drives or winchesters were created in 1956 by IBM. However, they were impractical. Their size exceeded the box, and the weight was almost equal to the ton. In this case, the volume of stored data did not exceed 3.5 megabytes. However, in the future, the standard developed, and by 1995 the plank was overcome in 10 gigabytes. And after another 10 years, Hitachi models of 500 gigabytes appeared on sale.
Unlike flexible analogues, hard drives contained aluminum plates. Data is reproduced by reading heads. They do not touch the disk, but work at a distance of several nanometers from it. One way or another, the principle of operation of the Winchesters is similar to the characteristics of the tape recorders. The main difference lies in the physical materials used for the production of devices. Hard disks became the basis of personal computers. Over time, such models began to be produced aligned together with drives, drives and electronics block.
In addition to the main memory required for data content, hard drives have a specific buffer needed to smooth the reading rates from the device.
3.5-inch diskettes
At the same time, movement in the sphere of small formats was moved. Knowledge of magnetic properties was useful when creating a diskette, the data from which was read using a special drive. The first similar analogue was presented with IBM in 1971. The record density on such information carriers was up to 3 megabytes. The basis of the floppy disk was a flexible disk that was covered with a special layer of ferromagnets.
The main achievement is to reduce the physical size of the carrier - made this format Main on the market for a quarter of a century. Only in the USA in the 80s, up to 300 million new diskettes were produced annually.
Despite the mass of advantages, the novelty had and disadvantages - sensitivity to magnetic effects and a small capacity compared to all the increasing needs of an ordinary user user.
CDs
The first generation of optical carriers became CDs. Their prototypes were still records. However, new external information carriers were made from polycarbonate. The disc from this substance received the finest coating of metal (gold, silver, aluminum). To protect the data, it was covered with a special varnish.
The notorious CD was designed by Sony and launched into mass production in 1982. First of all, the format got mad popularity due to convenient sound recording. The volume of several hundred megabytes allowed me to squeeze first vinyl playersand after and tape recorders. If the first inferior in the amount of information, the second differed in the worst sound quality. In addition, the new format sent a floppy disk, which not only contained less data, but were not too reliable.
CDs have caused the revolution in the field of personal computers. Over time, all the giants of the industry (for example, Apple) switched to PC production together with drives supporting CD format.
DVD and BLUE-RAY
The optical information carriers of the first generation lasted on the data storage conversion. In 1996, a DVD appeared, which by volume was more than six times. New standard allowed to record video greater duration. By him quickly set up the film industry. DVD films have become publicly available worldwide. The principle of operation and encoding information remains the same compared to CDs.
Finally in 2006 was launched new, today last format optical carrier information. The volume began to calculate hundreds of gigabytes. This is ensured best quality Sound and video records.
War formats
Over the past years, conflicts have become frequent between incompatible storage formats. External carriers different manufacturers At the next turn of the industry's development, they compete with each other in format.
One of the first such examples can be called a conflict between Edison Phonograph and Berliner Gramophone in the 10ths of the XX century. In the future, such disputes arose between CDs and 8-track audio cassettes; VHS and Betamax; MP3 and AAC, etc. The latter in this row became the "war" between HD DVD and Blue-Ray, which ended with the victory of the latter.
Flash drives
Examples of information media cannot do without mentioning USB flash drives. The first Universal Serial Bus was developed in the mid-90s. To date, there is already a third generation of this tire allows you to attach to a personal computer. peripheral device. And although this problem existed long before USB appeared, it was solved only in the last decade.
Today, each computer has a recognizable slot, with which you can connect to the computer. mobile phone, player, tablet, etc. Fast data transfer of any format made a USB truly universal tool.
Flash drives received the greatest popularity on the basis of this interface or in the flash drive. Such a device has a USB connector, a microcontroller, microcham, and a LED. All these details made it possible to keep in one pocket gigabytes of information. In its own way, it is also inferior to even floppy disks in 3 megabytes. At times, the volume of devices where information is stored. Media, on the contrary, tend to physically reduce.
The universality of the connector allows drives to work not only with personal computers, but also with TVs, DVD players and other devices with USB technology. A huge advantage in comparison with optical analogues has become less susceptibility to external influence. Flashke is not scary scratches and dust, formerly fatal threats for CD.
A virtual reality
In recent years, computer media is inferior to a virtual alternative position. Since today it is easy to connect a PC to a globally network, information is stored on common servers. Amenities are indisputable. Now to gain access to your files, the user does not need a physical medium at all. To interact with data at a distance, it is enough to be in the Wireless Access Area Wi-Fi connections etc.
In addition, this phenomenon helps to avoid misunderstandings with the failure of physical drives vulnerable to damage. Remote servers, the connection with which is supported by the signal, will not be affected, and in the case of unforeseen situations there exist backup storage data.
Output
Throughout history - from rock paintings to virtual bits - a person sought to make information carriers in bulk, more reliable and more affordable. This desire led to the fact that today we live in an era, which is not found without reason called the century information society. Progress reached the fact that now people are in their everyday life Just choke in the data stream. Perhaps information carriers whose species will always change drastically, according to the requirements of a modern person.
Prepress processes are presented special requirements To registering means used for storing information. Such requirements are a consequence of not only permanent needs associated with an increase in the volume of stored data processed in the process of production of printed products. Memory has an exceptional value for constant data backups within the workstation network, as well as for secure shipment and data archiving. Despite the increased data transmission capabilities through a network or via the Internet, the data environment will continue to play an important role in the exchange of information between the customer and the Contractor.
Thanks to new technologies and production processes, the capacity of carriers intended for storing information is constantly increasing. There are prerequisites that this growth will be about 80% per year. The essence of the increase in data storage includes, probably a set of following factors: increasing the record density, number of tracks and optimal use of the carrier surface. The superdisk with a memory capacity of 120 MB really corresponds to this task, despite the fact that appearance It is almost the same as a flexible 3.5-inch disk. However, the superdisc by the amount of memory exceeds the last almost 83 times. Information about the memory volumes of various media are given in Table. five.
Classification of data carriers
All currently available media can be divided by various features. First of all, energy-dependent and non-volatile information drives should be distinguished.
Non-volatile drives used for archiving and saving data arrays subdivided:
If quick access to information is required, such as, for example, when displaying or transmitting data, media with a rotating disk are used. For archiving performed periodically (backup), on the contrary, tape carriers are more preferred. They have large amounts of memory in combination with a low price, however, with relatively low speed.
For the purpose of information media differ in three groups:
- dissemination of information: media with pre-recorded information, such as CD ROM or DVD-ROM;
- archiving: media for one-time recording of information, such as CD-R or DVD-R (R (Record Able) for recording);
- reservation (Backup) or data transfer: Media with the ability to multiple information recording, such as floppy disks, hard disk, Mo, CD-RW (RW (RWRITABLE) - rewritable and tapes.
CD and DVD (ROM, R, RW)
CD-ROM was originally created in order to distribute large amounts of information (for example, music, etc.) for a reasonable fee. Meanwhile, it became the most used media information and for smaller data volumes, for example, with personal use. In the foreseeable future, CD-ROM can be replaced with DVD-ROM. DVD has a memory capacity from 4.7 to 17 GB. DVD-ROM can be used to distribute software products, multimedia, data banks and to record feature films. An increase in the amount of memory here was made possible by the technology of the double layer. It allows you to apply on the top and bottom sides of the disk for two cumulative layers, which are separated by a semi-reflective intermediate layer. When reading information, the laser "jumps" between both cumulative layers.
CD, briefly called CD-R (or, respectively, DVD-R) is an optical plate for a one-time recording in a 5.25 inches format with a large density. An entry on such a disk can be made only once in a special recording device. After that, information can be read through a conventional CD-ROM drive. A typical area of \u200b\u200bapplication is the transfer of information in limited quantities.
More flexible, but less common is CD-RW (Rewritable). This replaceable media can be overwritten to 1000 times. The applied layer when recording as a result of a thermopotic process changes its structure with crystalline to amorphous. As a result, the reflecting properties of the carrier layer change in these places. The intensity of radiation corresponding to the reflection from light or dark areas is converted to binary numbers 1 or 0.
Replaceable drives
The operation of a changeable drive is based on the use of magnetic layers serving for multiple information record.
Syquest interchangeable discs.
Superdisk, Zip, Jaz. Flexible disk 3.5 inches is the most common accumulator in the world. Currently, there are two systems in the development: IOMEGA ZIP technology and Superdisk (previously called LS-120) IMATION firm.
SuperDisk provides the ability to place information with a capacity of 120 MB and is almost no outwardly from the traditional 3.5-inch floppy disk. The carrier of information is inexpensive and "compatible in both directions", i.e. On new drives, you can also read and record classic disks 1.44 MB.
IOMEGA ZIP disks have a volume of 100 to 250 MB and are comparable to the SuperDisk media. The ZIP floppy disks are currently very common in the publishing business, from which it is possible to conclude on the relevant need for interchangeable media of this species. ZIP is not "compatible in both sides," and the drive can handle only ZIP media. Access time for information from the ZIP disk is less than that of the SuperDisk disk.
The 3.5-inch disks "JAZ" of IOMEGA have the amount of storage of information up to 2 GB. Magneto optical disk (CD-MO). Magneto-optical media, briefly referred to as Mo, gained widespread. In favor of this technology, the amount of memory is definitely said: 640 MB on a 3.5 inches carrier and 2.6 GB on a carrier of 5.25 inches. Their development goes quickly. Already today, manufacturers like Sony and Philips, talking about the volume of 2.6 GB of 3.5 inches media and 10.4 GB for carriers of 5.25 inch format. Mo drives reaches 4 MB / s data rates, and the average access time is less than 25 ms. Placing and record data are carried out by means of a laser.
Hard drives. Finally, you should mention hard drives that are included in the standard package of almost each computer. The amount of memory of these information carriers is constantly increasing in lately reached about 80 GB for 31/2 '' disc.