External memory- this is a place for long-term storage of data not used in this moment in the computer's RAM. External memory is non-volatile.
To work with external memory you must have drive and storage devices - carrier.
Main types of storage devices:
floppy drives magnetic disks(NGMD);
hard magnetic disk drives (HDD);
magnetic tape drives (TMD);
CD-ROM, CD-RW, DVD drives.
A hard magnetic drive is a random access information storage device based on the principle of magnetic recording. It is the main data storage device in most computers.
Information in the HDD is recorded on rigid (aluminum or glass) plates
Floppy disk, flexible magnetic disk - a portable, removable storage medium used for repeated recording and storage of data. Represents placed in a protective plastic case disk,. A floppy drive is used to read floppy disks. Floppy disks typically have a write-protect feature that allows read-only access to the data.
CD-ROM is a type of compact disc with read-only data recorded on it. CD-ROMs are a popular and cheapest means of distribution. software, computer games, multimedia
And other data.
Flash memory is a type of semiconductor electrically reprogrammable memory technology. The same word is used in electronic circuitry to designate technologically complete solutions of permanent storage devices in the form of microcircuits based on this semiconductor technology. In everyday life, this phrase is assigned to a wide class of solid-state information storage devices.
A logical disk is a part of a computer's long-term memory designed to store information on a hard drive. Logical drives are used to organize data located on a hard drive and make it easier to work with information.
A “logical disk” is the opposite of a “physical disk,” which refers to the memory of any particular disk medium.
The entire hard drive can be a logical disk, but for the convenience of working with information, as well as to ensure greater security, HDD usually divided into sections. It is recommended to leave a certain percentage of the total volume for the system partition hard drive. A hard drive is a physical device that you can see and touch with your hands. A logical disk simply does not exist physically; it is just one of the hard drive partitions.
External data storage devices somehow unexpectedly entered our lives. You could say it was a leap. Currently, people highly value the mobility of information, as well as the speed of its transmission. That is why an external drive is a very valuable device that allows you to quickly exchange movies, games and other files (it should be noted, even of considerable size) between two computer devices.
general information
The question that arose in connection with the problem of storing user data, as well as accessing it, is quite relevant. This problem is very acute in families where everyone tries to carve out as much space on the computer as possible specifically for their needs. And an external drive can easily become a solution to such problems.
The optimal solution at present is, of course, various network storage systems, which in many companies are located directly inside buildings. In general, they have quite a lot of advantages. Previously, creating a network storage required purchasing a separate computer that would play this role. Now, with the development wireless technologies, this was no longer necessary. Enough to put into action wireless router- and the problem is solved.
Modern models are available with support for USB version 3.0 ports. And this also has weight, because functionality are expanding significantly. What can you think of even better than network resource, located at home, which, if necessary, is quite possible to take with you on a trip? And this device will have so much mobile sizes, which will not burden absolutely anyone with its carrying!
In general, an external USB drive will be a solution to several problems at once. Models hard drives external type differ in characteristics, and in this article we will analyze several devices, get acquainted with them as a whole and in general, and understand what advantages and disadvantages they have. This is done so that anyone can then go to the store and, based on the material they have read, if necessary, choose an external drive model for themselves.
So, many hard drives now have interesting, innovative interfaces. This is about USB ports 3.0. They also have a large form factor. Next we will talk about whether it makes sense to purchase such disks, which are quite large in size and require power from an external source.
ADATA HD 710
This external memory drive is available in different versions, which differ in the amount of built-in memory. We are talking about allocating 500 gigabytes, 1 terabyte, and 2 terabytes. 500 GB, in our opinion, is now not enough for active use of the hard drive. But 1, and even more so 2 TB will be an excellent solution.
This external drive is available in three colors. The following colors are available: blue, yellow, black. All hard drives belonging to this series have a shockproof and waterproof casing. Lay down USB cable can be installed without any problems into the groove that was specially secured around the disk housing. Thus, the device developers solved the problem of convenient cable storage. Its length is about 30 centimeters. To be more precise, 31. The dimensions are quite average: with a weight of 220 grams, this is an external USB drive 3.0 has dimensions of 132 by 99 by 22 millimeters.
Hard drive. External hard drive HGST Touro Mobile MX3
This model, like its predecessor, has three modifications, equipped with different amounts of built-in long-term memory. We are talking about variations with a capacity of 500 gigabytes, as well as models with a capacity of 1 TB and 1.5 TB.
Among the shortcomings, it is worth noting the lack of legs that could combat the vibration of the hard drive during its operation. But the use of matte plastic as a housing material cannot be definitely considered. The USB cable doesn't fit anywhere. It has a length of 43 centimeters. This external hard drive is 126 millimeters long, 80 millimeters wide, and 15 millimeters high.
Seagate Expansion Portable
All Seagate models that belong to the Expansion series of portable external hard drives have the same form factor. It is equal to 2.5''. The model range of the series has three memory drives, which have corresponding volumes. This, according to the standard, is 500 gigabytes, 1 and 2 TB.
Like the model we reviewed earlier, the Seagate Expansion Portable does not have rubber feet. The housing of the series devices is made of matte plastic. These external storage devices have a USB cable 44 centimeters long. Dimensions of the hard drive are 122.3 millimeters in length, 81.1 millimeters in width, 15.5 millimeters in height. The mass of the drive is 170 grams.
Seagate Expansion
Models in this series differ from their predecessors not only in memory capacity, but also in their large form factor. It is 3.5''. Thus, the models automatically increase in size, weight, and also require an additional power source. The case of such hard drives is made of the same matte plastic. To combat the vibration that occurs during operation of the device, there are four rubber feet on its bottom. In the model range of this series you can see external hard drives with built-in memory capacity of 1, 2, 3, 4 and 5 terabytes.
The USB 3.0 cable is 118 centimeters long. For work hard drive will require a special power adapter. It operates at a voltage of 12 volts and a current of 1.5 amperes. The length of such a drive reaches 179.5 millimeters. The width is 118 millimeters, and its height is 37.5 mm. In this case, the mass of the drive is 940 grams.
Silicon Power Armor A80
External drives in this series have good body, protected from moisture penetration, as well as from mechanical damage. The outer surface of the hard drive is made of anodized matte aluminum. To counter the vibration that occurs when working with the drive, there are no rubber feet.
The lineup consists of drives with three different memory capacities. These are 1 and 2 terabytes, as well as 500 gigabytes. The models in the series are slightly different from all the external drives that we have reviewed before. The fact is that they have two cables at once, which are designed to synchronize the device with personal computer or laptop. The first cable is 79 centimeters long. The second one is 70 cm shorter. The case has an end where you can hide a short wire. Also hard disks series use socket USB type 3.0 A. All models that were described earlier use USB 3.0 Micro-B. Weighing 270 grams, the series hard drives measure 139.45 mm by 94 mm by 18.1 mm.
TOSHIBA Stor.E Basics
The body of this line of external memory drives is made of matte black plastic. There are four legs at the bottom of the gadget, which is good news. But as far as volume is concerned, the series may not please all users. The maximum amount of long-term memory available in such drives is 1 terabyte. The remaining two modifications of the series have capacities of 500 GB and 750 GB, respectively.
The USB 3.0 cable is not short, but not long either. Its length is 52.5 centimeters. It is interesting that the models in the series differ in size. The hard drive version, which has a capacity of 1 TB, weighs 180 grams and is 16.5 centimeters thick. At the same time, the remaining models will be thinner and lighter in terms of weight: their height is only 13.5 millimeters and their weight is 150 grams.
Transcend StoreJet 25H3
External drives of this brand have a casing that is covered with a rubber layer. Thus, the manufacturer took care of mechanical strength, adapting external hard drives of this series to unexpected mechanical shocks and loads. Models produced in the line have a memory capacity of 500 gigabytes, as well as 1 and 2 TB. If we talk about the color scheme, the hard drives of the series are available in purple and black, as well as in blue. The length of the cable for synchronization with a PC is about 45 centimeters.
Distinctive feature, feature of this model range is that there is a button on the case that serves for quick reconnection. It helps activate the special mode. In this case, there is no need to disconnect and turn off the hard drive, and then synchronize it with the computer again. With a weight of 216 grams, the 500 GB and 1 TB versions of the drive have the following dimensions: length - 131.8 mm, width - 80.8 mm, and thickness - 19 millimeters. The model, which is designed for 2 terabytes of internal memory, is slightly thicker (24.5 mm) and weighs a little more (284 grams).
Western Digital My Passport Ultra
Like almost all other models, the serial range of this external hard memory drive is made of matte black plastic. There are four feet at the bottom that will save the device from vibration during operation. The hard drive cover, depending on its modification, may be of different colors. Currently available in black, blue, red and metallic.
The amount of built-in memory is standard: 500 gigabytes, 1 TB or 2 TB. The USB cable does not fold anywhere, its length is 46 centimeters. A special bag made of velvet is provided for transportation. Weight (depending on the model) varies from 130 to 230 grams. dimensions also vary. The length can be from 110 to 110.5 millimeters, the width - from 81.6 to 82 millimeters. This is not so noticeable, but how the thickness of the hard drive increases with its memory capacity is visible quite clearly. It falls in the range from 12.8 to 20.9 millimeters.
External memory (ERAM) is designed for long-term storage of programs and data, and the integrity of its contents does not depend on whether the computer is turned on or off. This type of memory has a large capacity and low speed. Unlike RAM, external memory does not have a direct connection with the processor. Information from the OSD to the processor and vice versa circulates approximately along the following chain:
Part external memory computer includes:
hard disk drives;
floppy disk drives;
CD drives;
magnetic tape drives (streamers);
Magnetic-optical disk drives;
HDD
Hard disk (hard magnetic disk drives, HDD) is a type of permanent memory. Unlike RAM, data stored on a hard drive is not lost when the computer is turned off, making the hard drive ideal for long-term storage of programs and data files, as well as most important programs operating system. This ability (keeping information intact and safe after shutdown) allows you to remove a hard drive from one computer and insert it into another.
When turned on computer BIOS performs POST (power-on self-test) and checks whether there is a floppy disk in the drive. If there isn't one, it goes to the hard drive and copies a short program called "boot memory" from the hard drive to RAM. It then transfers control of the computer to a boot program, which oversees the loading of the operating system. Once the system is booted, boot program erases their memory, transferring control of the computer to a fully loaded operating system.
Hard drives are very reliable for storing large amounts of information and data. Inside a sealed hard drive are one or more inflexible disks coated with metal particles. Each disk has a head (a small electromagnet) built into an articulated arm that moves over the disk as it rotates. The head magnetizes the metal particles, causing them to line up to represent the ones and zeros of binary numbers. The motors that move the disc and lever are usually subject to wear and tear. Only the head can avoid wear, since it never comes into contact with the surface of the disc.
Another function of a hard drive is RAM simulation. By using sections of the hard drive as virtual memory, Windows can run more programs. The disadvantage of virtual memory is that it is slow compared to regular memory. If you set more, your computer will slow down.
The hard drive, or hard drive, is the most important component of a computer. It stores the operating system, programs and data. Without operating room Windows systems You can’t start the computer, and without programs you can’t do anything once it’s already booted. Without a data bank, you will have to enter information manually each time.
The hard drive is a mechanical device in the computer and can cause more problems than electronic devices. It's actually very reliable. The discs are collected in clean rooms in which the air is constantly filtered and dust particles are removed. Hard drives are assembled from magnetically sensitive material. Before the discs are taken out of the room, they are packaged and sealed. If you open your hard drive out of curiosity, you can say goodbye to it. To prevent this from happening, never do this - you cannot open them.
New hard drives must be formatted before use. This process consists of laying magnetic concentric paths and breaking them into small sectors, like pieces in a cake. Be careful: if data was written to the hard drive, formatting it will completely destroy it.
Due to the much larger number of tracks on each side of the disks and the large number of disks, the information capacity of a hard disk can be hundreds of thousands of times greater than the information capacity of a floppy disk and reach 150-200 GB. The speed of writing and reading information from hard drives is quite high (can reach 133 MB/s) due to the fast rotation of the disks (up to 7200 rpm).
IN hard drives rather fragile and miniature elements are used (carrier plates, magnetic heads, etc.), therefore, in order to preserve information and performance, hard drives must be protected from shocks and sudden changes in spatial orientation during operation.
Floppy disk drives
Disk drives (floppy disk drives (FDD)) come in two main types - for large floppy disks (5.25 inches in size, sometimes written 5.25"), and for small ones (3.5 inches, 3. 5"). A five-inch floppy disk can hold, depending on its type, from 360 information (360 thousand characters) to 1.2 MB. Three-inch cards, although smaller, hold more information (720 KB - 1.44 MB). In addition, the three-inchers are enclosed in a plastic case, and therefore are more difficult to break or dent. Standard drive for modern computers is a drive for small (3.5-inch) floppy disks. Hence its name in computer system- 3.5 A drive.
The 5-inch drive is located on system unit computer on the front and looks like a slot with a lever-latch into which the floppy disk is inserted and latched. The 3-inch drive has a smaller slot (by 2 inches), and instead of a latch it has a button.
A floppy drive is more similar to a magnetic tape drive than a hard drive. Its head physically contacts the floppy disk and thus magnetizes the surface, protected from dust by a moving flap that automatically retracts when the disk is inserted into the drive.
Floppy drives supply data to the system through a cable connected to a connector on motherboard. It is different from the IDE controller used for hard drives and the data transfer speed is much slower.
Floppy disk drives are becoming little used, but still necessary. They are used only for transferring small amounts of data from one computer to another, as well as for emergency computer startup. CD-ROM drives are the primary method for distributing new software, but they are not required by the computer to perform data processing functions.
Flexible magnetic disks. Two main types
floppy disk(eng. floppy disk) or floppy disk is a medium of small volume of information, which is a flexible plastic disk in a protective (plastic) shell. Used to transfer data from one computer to another and to distribute software.
In the center of the floppy disk there is a device for gripping and rotating the disk inside the plastic case. The floppy disk is inserted into the disk drive, which rotates the disk at a constant angular speed.
In this case, the magnetic head of the disk drive is installed on a certain concentric track of the disk, onto which information is written or from which information is read. The information capacity of a modern floppy disk is small and amounts to only 1.44 MB. The speed of writing and reading information is also low (only about 50 KB/s) due to the slow rotation of the disk (360 rpm).
In order to preserve information, floppy disks must be protected from exposure to strong magnetic fields (for example, do not place them next to a floppy disk mobile phone) and heating, since such physical effects can lead to demagnetization of the media and loss of information.
Currently, the most widespread are floppy disks with the following characteristics: diameter 3.5 inches (89 mm), capacity 1.44 MB, number of tracks 80, number of sectors on tracks 18 (Floppy disks with a diameter of 5.25" are now used very rarely, so their capacity does not exceed 1.2 MB, and besides, they are made of less durable material).The floppy disk is installed in a floppy-disk drive, is automatically fixed in it, after which the drive mechanism spins up to a rotation speed of 360 per minute. The diskette itself rotates in the drive, the magnetic heads remain stationary. The diskette rotates only when it is accessed. The drive is connected to the processor through a floppy disk controller.
Recently, three-inch floppy disks have appeared that can store up to 3 GB of information. They are manufactured according to new technology Nano2 and require special hardware for reading and writing, which is not yet included in standard package when purchasing a PC.
Floppy disk device
Floppy disks vary in size and capacity. By size, the division is made into floppy disks with a diameter of 5.25" (" - inch sign) and floppy disks with a diameter of 3.5". In terms of capacity - double density floppy disks (in English double density, abbreviation - DD) and high density (abbreviation - HD).
A 5.25" floppy disk consists of a protective plastic sleeve containing a magnetically coated plastic disk. This disk is thin and bends easily - that's why floppy disks are called floppy disks. Of course, you cannot bend the floppy disk, and this is prevented by the protective sleeve. The floppy disk has two holes - a large one in the center and a small one next to it. The large hole is designed to allow the magnetic disk to rotate inside the envelope.
This is done by a motor inside the drive. The inside of the protective envelope is covered with lint, which collects dust from the magnetic disk as it rotates. The small hole is used to count the revolutions of the disk inside the drive. The envelope has a longitudinal slot on both sides through which a disk with a magnetic coating is visible. Through this slot, a magnetic head inside the drive touches the disk and writes or reads data from it. Data is written to both sides of the disk. Never touch the surface of the magnetic disk with your fingers! By doing this, you can ruin it by scratching or greasy. If you turn the floppy disk with the slot facing you, with the label facing up, then on top right side envelope you will see a small rectangular cutout. If you cover it with pieces of sticky paper (usually sold with floppy disks), the disk will be write-protected. Typically, this cutout should be free; it should only be sealed on floppy disks with important data.
The structure of a 3.5" floppy disk is slightly different. Its protective sleeve is made of hard plastic, so such a floppy disk is more difficult to bend or break. The magnetic disk is not visible, since there are no open holes. There is a slot for access of the magnetic head to the surface of the disk, but it is covered with a latch. The latch is held closed by a spring. There is no need to open it by hand to avoid damaging the magnetic disk. Inside the drive, the latch opens automatically. There is a small latch on the floppy disk for write protection. You will see it on the top left of the floppy disk envelope if you hold the floppy disk with the large latch facing you , with the label facing down. The downward position for the write latch is normal, in this state the floppy disk is not write protected. To prevent data from being written to the floppy disk, slide the latch up, which will open a small square hole in the floppy disk.
Floppy disk recording method
The method of recording binary information on a magnetic medium is called magnetic coding. It lies in the fact that magnetic domains in the medium are aligned along paths in the direction of the applied magnetic field with their north and south poles. Usually there is a one-to-one correspondence between binary information and orientation of magnetic domains.
Information is recorded along concentric tracks (tracks), which are divided into sectors. The number of tracks and sectors depends on the type and format of the floppy disk. A sector stores the minimum amount of information that can be written to or read from disk. The sector capacity is constant and amounts to 512 bytes.
A CD-ROM writer can record any type of information - music, images or text. There are recordable discs on which you can write information only once (CD-R). But there are also rewritable discs (CD-RW), they are more expensive, but they allow you to erase information and add new information. However, if you burn music to a rewritable CD, you can only listen to it on a PC, but the rewritable disc can be played on any CD player.
Optical principle of recording and reading information.
IN laser discs CD-ROMs and DVD-ROMs use the optical principle of recording and reading information.
In the process of recording information on laser discs, various technologies are used to create surface areas with different reflectance coefficients: from simple stamping to changing the reflectivity of areas of the disc surface using a powerful laser. Information on a laser disk is recorded on one spiral-shaped track (like on a gramophone record), containing alternating sections with different reflectivity.
In the process of reading information from laser disks, a laser beam installed in the disk drive falls on the surface of the rotating disk and is reflected. Since the surface of the laser disk has areas with different reflection coefficients, the reflected beam also changes its intensity (logical 0 or 1). Then the reflected light pulses are converted using photocells into electrical pulses and transmitted via the highway to the RAM.
Subject to proper storage (in cases in a vertical position) and operation (without causing scratches or contamination), optical media can retain information for decades.
Laser drives and disks
Laser drives (CD-ROM and DVD-ROM) use the optical principle of reading information.
Laser CD-ROM (CD - Compact Disk) and DVD-ROM (DVD - Digital Video Disk) disks store information that was recorded on them during the manufacturing process. It is impossible to write new information to them, which is reflected in the second part of their names: ROM (Real Only Memory - read only). Such discs are produced by stamping and have a silver color.
The information capacity of a CD-ROM drive can reach 650-700 MB, and the speed of reading information in a CD-ROM drive depends on the rotation speed of the disc. The first CD-ROM drives were single-speed and provided information reading speeds of 150 KB/s. Currently, 52-speed CD-ROM drives are widely used, which provide 52 times faster information reading speed (up to 7.8 MB/s).
DVDs have a much larger information capacity (up to 17 GB) compared to CDs. First, lasers with shorter wavelengths are used, which allows the optical tracks to be placed more densely. Secondly, information on DVDs can be recorded on two sides, with two layers on one side.
The first generation of DVD-ROM drives provided information reading speeds of approximately 1.3 MB/s. Currently, 16-speed DVD-ROM drives achieve read speeds of up to 21 MB/s.
There are CD-R and DVD-R discs (R - recordable) that are golden in color. Information on such disks can be written, but only once. On CD-RW and DVD-RW (RW - ReWritable) discs, which have a "platinum" tint, information can be recorded many times.
For recording and rewriting onto discs, special CD-RW and DVD-RW drives are used, which have a fairly powerful laser that allows you to change the reflectivity of surface areas during the recording process. These drives allow you to write and read information from disks at different speeds. For example, marking a CD-RW drive “40x12x48” means that CD-R discs are written at 40x speed, CD-RW discs are written at 12x speed, and CD-RW discs are read at 48x speed.
Magnetic tape drives (streamers) and removable disk drives
Streamer (English tape streamer) - a device for Reserve copy large amounts of information. The media used here are magnetic tape cassettes with a capacity of 1 - 2 GB or more.
Streamers allow you to record a huge amount of information onto a small magnetic tape cassette. The hardware compression tools built into the tape drive allow you to automatically compress information before recording it and restore it after reading it, which increases the amount of stored information.
The disadvantage of streamers is their relatively low speed of recording, searching and reading information. At the moment, streamers are outdated and therefore they are used very rarely in practice.
Recently, storage devices on removable disks have become increasingly used, which allow not only increasing the amount of stored information, but also transferring information between computers. The volume of removable disks ranges from hundreds of MB to several gigabytes.
On this page we will talk about topics such as: , External computer memory, Magnetic storage, Hard drives, Winchester.
External computer memory, External storage devices.
External computer memory or VZU - important component electronic computer providing long-term storage programs and data on various media information. External storage devices(VZU) - can be classified according to a number of characteristics: by type of media, by type of design, by the principle of recording and reading information, by access method, etc. At the same time, under carrier refers to a material object capable of storing information.
External memory properties:
- The VRAM is non-volatile; the integrity of its contents does not depend on whether the computer is turned on or off.
- Unlike RAM, external memory has no direct connection with the processor.
The external memory includes:
- HDD – hard disk drives.
- NGMD – floppy disk drives.
- GCD – optical drives(CD-R, CD-RW, DVD).
- NML – magnetic tape drives(streamers).
- Memory cards.
Drives- This storage devices, designed for long-term (that is, independent of power supply) storage of large volumes of information.
In addition to its main characteristic - information capacity - disk drives are characterized by two other indicators: access time and speed of reading sequential bytes.
Hard disk drives.
Hard disk drive (HDD – Hard Disk Drive, hard drive) is a high-capacity storage device in which the storage media are round aluminum plates, both surfaces of which are coated with a layer of magnetic material. Used for permanent storage of information - programs and data. HDD usually called "Winchester"- that’s how one of the first models began to be called at one time Hard disk drives, which had the designation “30/30” and thus resembled the markings of famous weapons.
Note
It is also possible that the name comes from the place of initial development - a branch of IBM in Winchester (UK), where the technology for creating hard drives…
Winchester.
The surface of a disk is treated as a series of dot positions, each of which is considered a bit and can be set to 0 or 1. Since the locations of dot positions are not precisely determined, recording requires pre-applied marks to help the recording device locate the recording positions. The process of applying such marks is called physical formatting and is required before using the drive for the first time. Winchesters have a very large capacity: from hundreds of megabytes (the oldest) to tens of terabytes.
Structural elements of a hard drive.
Thin concentric circles are marked on each side of each plate (synchronizing marks are located along them). Each concentric circle is called a track. Groups of paths (tracks) of the same radius located on the surfaces of magnetic disks are called cylinders.
The number of the cylinder coincides with the number of the forming track. HDD may have several tens of thousands of cylinders.
Each track is divided into sectors. A sector is the smallest addressable unit of data exchange between a disk device and RAM. Sector numbering starts from 1. In order for the disk controller to find the desired sector on the disk, it is necessary to give it all the components of the sector address: cylinder number, surface number, sector number ().
operating system When working with a disk, it usually uses its own unit of disk space, called a cluster. Cluster (data storage cell) is the amount of disk space involved in a single read/write operation performed by the operating system.
Magnetic storage devices.
Floppy disk drive — floppy disk, diskette(English) floppy disk) – a device for storing small amounts of information, which is a flexible plastic disk in a protective shell. The most common are “three-inch floppy disks.” A 3.5 floppy disk has 2 working surfaces, 80 tracks on each side, 18 sectors on each track (512 bytes per sector).
Floppy disk device: The principle of recording on magnetic media based on the magnetization of individual sections of the magnetic layer of the carrier. Information is recorded along concentric tracks (tracks), which are divided into sectors. The number of tracks and sectors depends on the type and format of the floppy disk. A sector stores the minimum amount of information that can be written to or read from disk. The sector capacity is constant and amounts to 512 bytes.
Note
Today, floppy disks are outdated, they have been replaced by more reliable, high-speed and more capacious media - optical discs and memory cards...
Magnetic tape drives (streamers).
Streamer (English tape streamer)– a device for backing up large amounts of information. As carrier Magnetic tape cassettes with a capacity of 1 - 2 GB or more are used here. The disadvantage of streamers is their relatively low speed of recording, searching and reading information.
Note
Today, streamers are outdated and practically not used...
On this this article I'm finishing, I hope you have fully understood the topics: External storage devices, External computer memory, Magnetic storage, Hard drives, Winchester.
The main function of external memory is the ability to store information for a long time. In addition, external memory has a large capacity and is cheaper than RAM. And yet, external memory media ensure the transfer of information from one computer to another, which is important in a situation where there are no computer networks.
Thus, external (long-term) memory- this is a place for long-term storage of data (programs, calculation results, texts, etc.) not currently used in the computer’s RAM. External memory, unlike RAM, is non-volatile and has no direct connection with the processor.
To work with external memory, you must have a drive (a device that provides recording and (or) reading of information) and a storage device - a carrier.
Main types of storage devices:
floppy magnetic disk drives (FMD);
hard magnetic disk drives (HDD);
CD-ROM, CD-RW, DVD drives. The main types of media correspond to them:
flexible magnetic disks (Floppy Disk);
hard magnetic disks (Hard Disk);
CD-ROM, CD-R, CD-RW, DVD discs. Main characteristics of drives and media:
information capacity;
speed of information exchange;
reliability of information storage;
The basis for recording, storing and reading information from external memory is based on two principles - magnetic and optical. Thanks to these principles, information is retained even after the computer is turned off.
floppy disk
A floppy disk drive or floppy disk is a storage medium for a small amount of information, which is a flexible disk in a protective shell. Used to transfer data from one computer to another and to distribute software.
The disc is located inside a plastic sleeve, which protects it from mechanical damage. They may be damaged if:
touch the recording surface;
write on the floppy disk label with a pencil or ballpoint pen;
bend a floppy disk;
overheat the floppy disk (leave it in the sun or near a radiator);
expose the floppy disk to magnetic fields
The disk inside the drive rotates at a constant angular speed, which is quite low (several kilobytes per second, average access time - 250 ms). Information is written to both sides of the disk. Currently, the most common floppy disks are 3.5 inches in size (1 inch = 2.54 cm) and have a capacity of 1.44 MB. The disc can be write protected. A safety latch is used for this purpose. Floppy disks require careful handling.
Hard magnetic disk
The hard drive is informational
computer warehouse and is capable of storing
huge amounts of information.
Hard magnetic storage
disks(English)HDD - HardDiskDriver)
or Vinchester- this is the most widespread Fig.2. Hard magnetic disk
a high-capacity storage device in which the information carriers are aluminum plates, both surfaces of which are coated with a layer of magnetic material. Used for permanent storage of programs and data. Hard drives are placed on one axis and, together with the read/write heads and the heads that carry them, are placed in a hermetically sealed metal case. This design made it possible to significantly increase the disk rotation speed and recording density. Information is recorded on both surfaces of the disks
Unlike a floppy disk, a hard disk spins continuously. The platters in a hard drive rotate at a certain speed (also called spindle speed), which can be 3,600, 4,200, 5,400, 7,200, 10,000 or 15,000 rpm
Therefore, its rotation speed can be from 3600 to 10000 rpm, data search time - from 2 to 6 ms, data transfer speed - up to 300 MB/sec. The capacity of hard drives in computers is measured in tens of gigabytes. The most common drives with a diameter of 0.8, 1, 1.8, 2.2 inches.
In order to preserve information and performance, the hard drive must be protected from shocks and sudden changes in spatial orientation during operation.
Laser disc
CD- ROM(English)CompactDiskRealOnlyMemory-I constantly remembergeneral device based on a CD)
The CD has a diameter of 120 mm (about 4.75 inches) and is made of polymer and coated with a metal film. Information is read from this metal film, which is coated with a polymer that protects the data from damage. CD-ROM is a one-way storage medium.
The principle of digital recording of information on a laser disk differs from the principle of magnetic recording. The encoded information is applied to the disk with a laser beam, which creates microscopic depressions on the surface, separated by flat areas. Digital information is represented by alternating depressions (coding zero) and light-reflecting islands (coding one). The information stored on the disk cannot be changed.
Data access on a CD-ROM is faster than data on floppy disks, but slower than on hard drives (150 to 400 ms at speeds up to 4500 rpm). The data transfer speed is at least 150 KB and reaches 1.2 MB/s. CD-ROM capacity reaches 780 MB, due to which multimedia programs are usually released on them.
CD-ROMs are simple and easy to use, have a low unit cost of data storage, practically do not wear out, cannot be affected by viruses, and it is impossible to accidentally erase information from them.
CD-R (Compact Disk Recorder)
CD-R is a recordable disc with an average capacity of 700 MB (80 minutes). On CD-R discs, the reflective layer is made of gold film. Between this layer and the base there is a recording layer of organic material that darkens when heated. During the recording process, the laser beam heats selected points on the layer, which darken and stop transmitting light to the reflective layer, forming areas similar to depressions. CD-R drives, thanks to their significant reduction in price, are becoming increasingly widespread.
CD-RW (Compact Disk Rewritable)
More popular are CD-RW drives, which allow you to write and rewrite information. The CD-RW drive allows you to write and read CD-R and CD-RW discs, read CD-ROM discs, i.e. is in a certain sense universal.
The abbreviation DVD stands for DigitalVersatileDisk, i.e. uniuniversal digital disk. Having the same dimensions as a regular CD and a very similar operating principle, it holds an extremely large amount of information - from 4.7 to 17 GB. Perhaps it is precisely because of its large capacity that it is called universal. True, today the DVD disc is actually used in only two areas: for storing video films (DVD-Video or simply DVD) and ultra-large databases (DVD-ROM, DVD-R).
The discrepancy in capacities arises as follows: unlike CD-ROMs, DVDs are recorded on both sides. Moreover, one or two layers of information can be applied on each side. Thus, single-sided single-layer discs have a capacity of 4.7 GB (they are often called DVD-5, i.e. discs with a capacity of about 5 GB), double-sided single-layer - 9.4 GB (DVD-10), single-sided double-layer - 8.5 GB (DVD-9), and double-sided double-layer - 17 GB (DVD-18).
In order to preserve information, laser discs must be protected from mechanical damage (scratches), as well as from contamination.
Flash-memory
Flash-memory is a volatile type of memory that allows you to record and store data in microcircuits. Flash memory cards do not have moving parts, which ensures high data safety when used in mobile devices
(laptop computers, digital cameras, etc.)
Flash memory is a chip housed in a miniature flat package. To read or write information, the memory card is inserted into special drives built into mobile devices or connected to a computer via a USB port. The information capacity of memory cards is different, it can reach from 512 MB to 4 GB, 8 GB, 16 GB, 32 GB, 48 GB. Transcend has updated the popular JetFlash V20 series of USB flash drives by releasing a new model with a capacity of 64 GB.
The disadvantages of flash memory include the fact that there is no single standard and different manufacturers produce memory cards that are incompatible with each other in size and electrical parameters.
Loading...
