Long-term memory of the computer. Storage devices

The computer serves to increase efficiencywork of man. But what would it have value if it could not store the data? In this it helps the main and external (long-term) memory of the computer. And although the main topic of the article is the second one, for completeness of the picture one section within the framework of the article will be given to the first one.

What is the main memory?

It includes:

1. Random Access Memory. It is volatile, and when you turn off the computer, all the information that was stored on it disappears.
2. Read-only memory. It is non-volatile. It contains information that should not be changed. First of all, it refers to the configuration of the PC and the software that conducts the testing of the component devices before the operating system is loaded. Also, one of the most important components is stored here - the basic input / output system, known as the BIOS. It should be noted that ROM and long-term computer memory have much in common. But due to the difference in the importance of the stored information, they are shared.

External memory

This is the place where long-term storagethere are a variety of data that are not currently used by the operational component of the computer. They include various programs, results of calculations, texts and so on.

External memory is nonvolatile. It is also convenient to transport in cases where computers are not connected to a local or global network. To work with external memory, you need to acquire a drive. This is a special device (a), which ensures the recording and reading of information. Also necessary are storage mechanisms - carriers.

Significant difference of long-term memory fromoperational is that it does not have a direct connection to the processor. This gives some inconvenience in the form of the need to complicate the structure of the PC. Therefore, the operative and long-term memory of the computer work together: from the second data is transferred to the first, and then through the cache or directly to the processor.

What is included in the external memory?

To understand what we are dealing with, it is necessary to imagine the data of the external memory device. So, to it belong:

1. Drives on hard magnetic disks. The size of the data store is used as an indicator of the amount of information that can be stored on the computer.
2. Hard drives on floppy disks. Outdated. Used to transfer programs and documents between computers.
3. Drives on CDs. Used to store large amounts of data.
4. Flash Drives. They are used to store large amounts of data in small objects.
5. External memory includes all other drives that can be moved to other computers without problems. As a rule, they are outdated and out of circulation.

Classify

Storage devices are divided into types and categories. As the cornerstone take the principles of their functioning, operational-technical, software, physical and other characteristics. Each device has its own technology for recording / storing / reproducing digital information. Main characteristics that are important for users (they can also be classified according to them):

1. Speed ​​of data exchange.
2. Information capacity.
3. Reliability of data storage.
4. The cost.

Here on such parameters memory devices differ. Of course, there are many other characteristics, but they will be of interest only to professionals.

Magnetic devices

The principle of operation of these instruments is based onstorage of information, which uses the magnetic properties of materials. In the devices themselves, as a rule, there are components responsible for reading / writing and magnetic media on which everything is stored. The latter is divided into species depending on their physical and technical characteristics and performance characteristics. Most often allocate tape and disk devices. They have a common technology: thus, by magnetizing with an alternating magnetic field, information is written and read. These processes are usually performed along concentric fields. These are special tracks that are on the entire plane of the rotating carrier. Recording is carried out in the digital code.

Magnetization takes place thanks touse the read / write heads. They represent at least two controlled magnetic circuits with cores. An alternating voltage is applied to their windings. If its value changes, then the same applies to the direction of the lines of the magnetic field. When this process occurs, the value of the information bit changes from 0 to 1 or from 1 to 0. This is how this long-term memory of the computer is arranged.

Despite the apparent complexity and slownesswork of such a scheme, we dare to assure you that these assumptions are unjustified. Thus, a computer from modern hard magnetic disks can extract huge amounts of information at certain points in time. If you derive the efficiency factor, then the external memory devices released in the last few years will have it hundreds and thousands of times larger than those that were created two decades ago.

Organization

Data for the operating system are systematizedand are combined into sectors and tracks. The last in the number of forty or eighty pieces are narrow concentric rings on the disk. Each track is divided into separate parts, which are called sectors. When read or write is performed, an integer is always read. And it does not depend on the amount of information that is requested. The size of one sector is 512 bytes.

Also it is necessary to familiarize with such term ascylinder. This is the name of the total number of tracks from which you can read information without moving the heads. The data location cell (or cluster) is the smallest area of ​​the disk that is used by the operating system to write files. Usually they are understood as one or more sectors.

About the drives. Hard disks

The greatest importance for working with moderncomputers have hard disks as storage for us. In them, in one case, the media, the read / write device and the interface part (often also called the controller) are often combined. Here such devices are combined into special chambers, where they are on the same axis and work with a block of heads and a common driving mechanism. Hard drives at the moment are the most capacious widely used devices - now few people will be able to surprise the store of information for 1 or even 10 terabytes. But this still affects the speed of the operation. So, when the work is just beginning, the process of reading data can take more than a dozen seconds. Although, if compared with older models, the speed progress is obvious.

About storage devices: portable devices

Hard drives, as has been repeatedlyunderlined, can store a significant amount of data, but their re-installation from one computer to another is not an easy task. And then portable devices come to the rescue.

These are special mechanisms by whichyou can transfer data between different computers without significant problems. The amount of external memory is not as large as that of hard drives, but thanks to the ease of transportation and the connection (and then reading out the information), they found their niche. Now the most popular are two types of similar devices: flash drives and optical disks. Each of them has advantages and disadvantages, but in the world there has long been a tendency for its gradual capture by the first type of devices.

Conclusion

As you can see, to the long-term memory of the computerthere are quite a lot of different devices. All of them provide data storage for a considerable period of time, as well as the possibility of their retrieval.

Summing up, we can say that the long-term memory of the computer fully fulfills the functional assigned to it.