A computer serves to increase the efficiency of a person. But what value would it have if it could not store data? In this he helps the main and external (long-term) computer memory. Although the main topic of the article is the second, for completeness, one section of the article will be devoted to the first.
What is the main memory?
It includes:
- Random access memory It is volatile, and when you turn off the computer, all the information that was stored on it disappears.
- Read only memory It is non-volatile. It contains information that should not change. First of all, it includes PC configuration and software, which tests component devices before loading the operating system. It also stores one of the most important components - 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 because of the difference in the importance of the stored information, they are separated.
External memory
This is the name of the place where a variety of data is stored for long-term storage that is currently not used by the operational component of the computer. These include various programs, calculation results, texts and more.
External memory is non-volatile. It is also convenient to transport it in cases where computers are not connected to a local or global network. To work with external memory, you need to get a drive. This is a special device (a) that provides the recording and reading of information. Storage mechanisms - carriers are also necessary.
A significant difference between long-term memory and operational memory is that it does not have a direct connection with the processor. This causes certain inconvenience in the form of the need to complicate the structure of the PC. Therefore, the operational and long-term memory of the computer work together: from the second, the 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, you need to imagine the data of an external memory device. So, they include:
- Hard disk drives. The size of the data storage is used as an indicator of the amount of information that can be stored on the computer.
- Floppy disk drives. Outdated. Used to transfer programs and documents between computers.
- CD drives. Used to store significant amounts of data.
- Flash drives. They are used to store significant amounts of data in small objects.
- External memory includes all other drives that can be easily moved to other computers. As a rule, are outdated and out of circulation.
We classify
Storage devices are divided into types and categories. As the cornerstone accept the principles of their functioning, operational, technical, software, physical and other characteristics. Each device has its own technology for recording / storage / playback of digital information. The main characteristics that are important for users (you can also classify them):
- The speed of data exchange.
- Information capacity.
- Reliability of data storage.
- Cost.
These are the parameters that make storage devices different. Of course, there are many more different characteristics, but they will be of interest exclusively to professionals.
Magnetic devices
The principle of operation of these devices is based on the storage of information, which uses the magnetic properties of materials. In the devices themselves, as a rule, there are components responsible for reading / writing and a magnetic medium on which everything is stored. The latter is divided into types depending on their physical and technical characteristics and performance characteristics. Most often, tape and disk devices are distinguished. They have a common technology: for example, using magnetization with an alternating magnetic field, information is applied and read. These processes are usually performed along concentric fields. These are special tracks that are located on the entire plane of the rotating media. Recording is carried out in digital code.
Magnetization is accomplished through the use of read / write heads. They are at least two controllable 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 device of long-term computer memory is arranged.
Despite the apparent complexity and slowness of the operation of such a scheme, we dare to assure you that these assumptions are unjustified. So, a computer from modern hard magnetic disks can extract huge amounts of information for individual moments of time. If we derive the efficiency coefficient, 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 is systematized and combined into sectors and tracks. The last forty or eighty pieces are narrow concentric rings on the disk. Each track is divided into separate parts, which are called sectors. When reads or writes are made, their 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.
You should also familiarize yourself with a term such as a cylinder. This is the total number of tracks from which information can be read without moving the heads. A data placement cell (or cluster) is the smallest disk area that the operating system uses to write files. Usually they mean one or several sectors.
About drives. Hard disks
The most important thing for working with modern computers as storage of information for us are hard drives. In them, the media, reader / writer and the interface part (often also called the controller) are often combined directly in one housing. These devices are combined in special chambers, where they are on the same axis and work with the head unit and the common drive mechanism. Hard drives are currently the most capacious widely used devices - now few people will be able to surprise the information store for 1 or even 10 Terabytes. But this still affects the speed of the operation. So, when the work just starts, the process of reading data can take more than a dozen seconds. Although, when compared with older models, performance progress is evident.
About drives: portable devices
Hard drives, as has been repeatedly emphasized, can store significant amounts of data, but moving them from one computer to another is not an easy task. And here portable devices come to the rescue.
These are special mechanisms through which data can be transferred between different computers without significant problems. The amount of external memory they have is not as large as that of hard drives, but thanks to the ease of transportation and connection (and then reading information) they found their niche. Now the most popular are two types of such devices: flash drives and optical drives. Each of them has its own advantages and disadvantages, but in the world there has long been a trend towards its gradual capture by the first type of devices.
Conclusion
As you can see, quite a few different devices belong to the long-term memory of a computer. All of them provide data storage for a significant period of time, as well as the ability to retrieve it.
Summing up, we can say that the long-term memory of the computer fully fulfills the functionality assigned to it.