A computer is a complex machine that not everyone can master. Remember your grandparents: how difficult it is for them to understand how a PC works, what it takes to turn it on and how to control a mouse. To understand why when you turn off the computer information is erased, it is important to understand the basic principles of the device.
Memory
Computer memory is an extremely important function. Each user needs a PC to store information. Any program needs to have data either temporarily or permanently in the OS. The Internet also uses memory, storing data in special folders.
It is important that the computer has the ability to store information for a long time. In order for the system to work correctly, it uses memory.
Types
Often at computer science lessons they ask the question of where the information is erased from when the computer is turned off. To answer it, you need to understand what kind of memory exists, where temporary files are, and where the data is stored on an ongoing basis.
So, the computer has internal and external memory. The first option contains fast and volatile memory as a separate subspecies. Also internal may be constant. The first subtype is represented by RAM and cache, and the second subtype is ROM and CMOS.
External memory means drives such as flash drives, disks, etc.
Organization
It is known that when the computer is turned off, the information disappears, it is erased from a certain type of memory. It is just about the internal memory. It does not remain when you turn off the PC. The memory itself is represented by a set of cells that store materials. Each such block has its own address.
Cell sizes, data types - all this can be different depending on the PC. For example, in older computer models, often the cells were large, one could reach 64 bits. This type of block was called "words."
Classification
In general, classifying any memory is not so simple. There are several options for how to do this. Everything will depend on the classification parameters. For example, computer memory can be allocated as intended:
- Temporary allows you to save intermediate processing results.
- Corrective saves the addresses of cells that are damaged.
- The manager contains control programs and is often presented in the form of ROM.
- The buffer room stores information when exchanging it between different devices or applications.
- The cache stores the data that is most often used, providing quick access to it.
- Shared is immediately open to a number of users, actions or chips.
Address space also allows you to divide memory into three types:
- Real or physical memory has a physical data location.
- Virtual does not have a physical location.
- Overlay has just a couple of areas with one address, but only one can be available.
Operational
So, when you turn off the computer, the information is erased from the RAM. RAM - the volatile component of the PC. It stores a special machine code that is generated while the PC is running. Also, the RAM can be filled with input, output and intermediate data on which the chip is working.
Exchange
Such memory should move freely from the processor to RAM and vice versa. She does this in two ways. The first is directly, the second is through the processor register or cache.
Modern RAM semiconductor. It collects data and saves when electricity is supplied to the modules. If you turn them off for a short and long time, the data can either be distorted or completely destroyed.
Alternative
Mother memory has an energy-saving mode of operation. The PC goes into "sleep", while the energy consumption of the device is reduced. Despite the fact that hibernation leads to the fact that the power of the RAM is turned off, the information is saved. To do this, the entire system transfers the contents to a permanent storage device. In this case, the hard drive is most often used.
In general, information about programs and operating system data is collected on RAM. For everything to work stably, you need a large supply of RAM. The multitasking of the PC and how stable all processes will go will depend on this.
Modules
Now you understand where the information is erased when you turn off the computer. But what does RAM actually look like? In modern PCs, it is represented by plates - modules. They are dynamic and have semiconductor integrated circuits. Users use RAM when they are talking specifically about these modules, since they are considered a storage device.
The modules are organized according to the scheme of devices with random access. The dynamic type is somewhat cheaper than the static type. It has a high density. Therefore, on the same area of the silicon crystal fits more memory blocks. But it is cheaper because significantly reduced performance.
Static RAM is correspondingly more expensive because it is faster. This trend has caused the growth of dynamic type modules, since it is easier to produce. The static version is designed for microprocessor cache memory.
Dynamic
When you turn off the computer, all information is erased. The reasons for this lie in the type of RAM itself. To understand this, consider both types more similarly.
Dynamic type as we found out more economical. It stores bits in a specific pattern. It consists of a capacitor and a transistor. There are options with two capacitors. This type is economical, since the circuit itself is 1 bit cheaper than several transistors. Also, such a number of elements requires a smaller area on the crystal.
The dynamic type is called DRAM. Despite the advantages, he also has disadvantages. For example, its operation is slower, since a change in the state of a trigger at the input is faster than in the case of a capacitor. This is because the capacitor must first be charged and discharged, and this takes more time than normal trigger switching.
Another drawback is that after a certain time, the capacitor discharges. They discharge faster if their capacity is small, and the current leakage, on the contrary, is impressive.
Static
After turning off the computer, information is erased regardless of the type of memory. Even if we have static modules in front of us, all the same, after the power is cut off, the data is destroyed. This is because any RAM is volatile and works correctly only when electricity is supplied.
Static memory is named SRAM. This is a RAM that does not need to be generated. Has random access. The advantage of this option is speed. There are triggers in the circuit. Thanks to their work, switching does not take much time. But there are drawbacks to this type. Since there are many transistors in the trigger, this is expensive. Such a group, in addition to its weight, takes up a lot of space on the crystal.
Cache
After turning off the computer, all information is also erased from the cache. This is a super-operative memory, which, incidentally, often consists of a static type. Presented by a fast storage device with a small volume. Used memory when exchanging information. Data moves from microprocessors to RAM and vice versa. The speed is due to the fact that it is necessary to compensate for the difference in speed due to different amounts of data.
If in the case of RAM the device is modules, then in the case of the cache, the controller takes over the work. He works as a software "psychic." In the case of launching a specific application, it tries to predict what information the processor may need in the near future. Therefore, it quickly loads them into memory.
It is worthwhile to understand that in this case there is a chance of both guessing and making a mistake. If the controller correctly predicted, then the necessary data is quickly retrieved from the cache. If there is no information there, then the processor extracts it from the RAM. This process is correspondingly somewhat slower.
The cache is located on a static type of microchips. They are fast, small and expensive. Now microprocessors consist of a built-in cache memory, which can be represented at different levels. The first step has a size of up to 384 Kb. A second level with a capacity of up to 12 MB can also be installed.
ROM
When you turn off the computer, information is erased from the internal memory. But it is not so. As far as we know, volatile and constant are referred to internal memory. So, it is the permanent storage device (ROM) that is considered non-volatile, which means that the information from it does not disappear anywhere after turning off the PC.
This option is referred to as ROM. This is a memory that can save data, but cannot change it. Therefore, the option is needed only for reading information from it. Often this type is used to record commands designed to start the system. This again proves to us that all the information is not erased from the ROM after turning off the computer.
Recovery
What to do if you work with programs and documents, and when the computer is disconnected from the network, the information disappears? Usually this question is asked by those who have suddenly turned off the electricity.
It is important to understand immediately that file loss is not so scary in this case, as a power surge, which will lead to component breakdown. Therefore, if this happened to you, it is better to disconnect the PC from the outlet. So you protect the motherboard from combustion or the hard drive from damage.
After resuming work, you need to check what data has been lost. If you worked with a document in Word, then most likely the program managed to create a backup copy with the last saved changes. Some applications during emergency shutdowns can save temporary copies of projects that they worked with before shutdown.
If, nevertheless, something important was lost, you can try to recover the data using the program. There are many of these on the Internet. They help scan the disk, see lost or corrupted data.
conclusions
Remember that when you turn off the computer, information is erased only from RAM or cache. Your personal data is not saved there, so you will not lose anything important. Usually, the RAM contains program information that is needed at a particular moment. Most often these are codes for quick resumption of work with programs, downloaded information from individual sources, etc.