Computer Science, Cybernetics and Programming

Storage of data information is not an independent phase in the information process but is part of the processing phase. Distinguish structured data which reflects individual facts of the subject area is the main form of data presentation in the DBMS and unstructured arbitrary form including text and graphics and other data. This form of data presentation is widely used, for example, in Internet technologies, and the data itself is provided to the user in the form of a response. search engines. Organization of one or ...

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Question 2. Data storage.

Storage of information (data) is not an independent phase ininformation processbut is part of the processing phase. However, due to the importance of organizing storage, this material is placed in a separate section.

Distinguish structured datawhich reflects individual facts of the subject area (this is the main form of data presentation in the DBMS), andunstructuredarbitrary in form, including texts, graphics, and other data. This form of data presentation is widely used, for example, in Internet technologies, and the data itself is provided to the user in the form of a response by search engines.

The organization of this or that type of data storage (structured or unstructured) is associated with providing access to the data itself. By access is meant the possibility of distinguishing a data element (or a set of elements) among other elements according to some criteria in order to perform some actions on the element. In this case, an element is understood as a file record (in the case of structured data), and the file itself (in the case of unstructured data).

For data of any kind, access is carried out using special data calledkey (keys ) For structured data, such keys are part of file records as separate record fields. For unstructured search words or phrases are usually included in the search text. Using the keys, the required elements are identified in the information array (data storage array).

A further description of the information storage phase relates to structured data.

Models structured dataand technologies for their processing are based on one of three ways of organizing data storage: in the formlinear list  (or tabular), hierarchical (or tree-like),networked.

Data storage- this is its record in auxiliary storage devices on various media  for later use.

Storage is one of the main operations carried out on information, and the main way to ensure its availability for a certain period of time.

The main content of the process of storing and accumulating information is to create, record, replenish and maintain information arrays and databases in an active state.

As a result of the implementation of such an algorithm, a document, regardless of the form of presentation, received in the information system, is processed and then sent to the repository (database), where it is placed on the appropriate "shelf" depending on the accepted storage system. The processing results are transferred to the catalog.

The information storage stage can be represented at the following levels:

External;

Conceptual, (logical);

Domestic;

Physical.

External level reflects the information content and presents methods (types) of data presentation to the user during the implementation of their storage.

Conceptual the level determines the organization of information arrays and methods of storing information (files, arrays, distributed storage, concentrated, etc.).

Inner levelrepresents the organization of storage of information arrays in its processing system and is determined by the developer.

Physical levelstorage means the implementation of the storage of information on specific physical media.

Methods of organizing the storage of information associated with its search - an operation involving the extraction of stored information.

Storage and retrieval of information are not only operations on it, but also involve the use of methods for performing these operations. Information is stored so that it can be found for future use. The ability to search is laid during the organization of the memorization process. To do this, use methods of marking memorized information that provide search and subsequent access to it. These methods are used to work with files, graphic databases, etc.

Fig. 1 Algorithm for the process of preparing information for storage

Marker - a label on the information carrier indicating the beginning or end of the data or its part (block).

In modern storage media, markers are used:

Addresses (address marker) - a code or physical label on the track of the disk, indicating the beginning of the sector address;

Groups - a marker indicating the beginning or end of a data group;

Tracks (beginning of a turn) - an opening on the lower disk of a package of magnetic disks indicating the physical beginning of each track of a package.

Protections - a rectangular cut-out on a medium (cardboard package, envelope, magnetic disk) that allows performing any operations on data: writing, reading, updating, deleting, etc .;

End of file - a label used to indicate the end of reading of the last record of a file;

Tapes (tape marker) - a control record or physical label on magnetic tape, indicating the sign of the beginning or end of a data block or file;

A segment is a special label recorded on magnetic tape to separate one segment of a data set from another segment.

Information storage in a computer is connected both with the process of its arithmetic processing, and with the principles of organizing information arrays, searching, updating, presenting information, etc.

An important stage of the automated storage phase is the organization of information arrays.

Array - an ordered set of data.

Information array– information storage system, including the presentation of data and the relationships between them, i.e. principles of their organization.

Information is stored on special media. Historically, the most common medium of information was paper, which, however, is unsuitable under ordinary (not special) conditions for long-term storage of information. For electronic computers, the following machine media are distinguished by the material of manufacture: paper, metal, plastic, combined, etc.

According to the principle of exposure and the possibility of structural changes, magnetic, semiconductor, dielectric, perforation, optical, etc. are distinguished.

By the method of reading distinguish contact, magnetic, electrical, optical. Of particular importance in the construction of information support are the characteristics of access to information recorded on the medium. Allocate direct and sequential access media. The suitability of the medium for storing information is evaluated by the following parameters: access time, memory capacity and recording density.

Thus, we can conclude that the storage of information represents the process of transmitting information over time, associated with ensuring the invariability of the state of the material medium.

Data storage

Information encoded using natural and formal languages, as well as information in the form of visual and sound images, is stored in the human memory. However for long-term storage  information, its accumulation and transmission from generation to generation are usedinformation carriers.

The material nature of information carriers can be different: DNA molecules that store genetic information; paper on which texts and images are stored; magnetic tape on which sound information is stored; photo and film films on which graphic information is stored; memory chips, magnetic and laser disks on which programs and data are stored in a computer, and so on.

According to experts, the amount of information recorded on various media exceeds one exabyte per year (1018   byte / year). About 80% of all this information is stored digitally on magnetic and optical media, and only 20% is stored on analog media (paper, magnetic tapes, photo and film films). If all the information recorded in 2000 was distributed to all the inhabitants of the planet, then 250 MB would be required for each person, and 85 million would be required for its storage hard magnetic  20 GB drives.

Information capacity of information carriers.  Storage media are characterized by information capacity, that is, the amount of information that they can store. The most information-intensive are DNA molecules that are very small in size and tightly packed. This allows you to store a huge amount of information (up to 1021 bits in 1 cm 3 ), which allows the body to develop from a single cell containing all the necessary genetic information.

Modern memory chips allow you to store in 1 cm3 to 10 10   bits of information, however, it is 100 billion times smaller than in DNA. We can say that modern technology is still significantly losing biological evolution.

However, if we compare the information capacity of traditional storage media (books) and modern computer storage mediathen the progress is obvious. Each floppy disk can hold a book of about 600 pages, and a hard disk or DVD contains a whole library of tens of thousands of books.

Reliability and durability of information storage. Of great importance is the reliability and durability of information storage. DNA molecules are more resistant to possible damage, since there is a mechanism for detecting damage to their structure (mutations) and self-healing.

Reliability (resistance to damage) is high enough for analog media, the damage of which leads to the loss of information only in the damaged area. The damaged part of the photo does not deprive the opportunity to see the rest, damage to the portion of the magnetic tape only leads to temporary loss of sound and so on.

Digital media  much more sensitive to damage, even the loss of one bit of data on a magnetic or optical disk can lead to the inability to read the file, that is, to the loss of a large amount of data. That is why it is necessary to follow the rules of operation and storage of digital storage media.

The most long-term carrier of information is a DNA molecule that, for tens of thousands of years (humans) and millions of years (some living organisms), retains the genetic information of this species.

Analogue media can store information for thousands of years (Egyptian papyri and Sumerian clay tablets), hundreds of years (paper) and decades (magnetic tapes, photo and film).

Digital media has appeared relatively recently and therefore their durability can only be judged by expert estimates. According to expert estimates, with proper storage, optical media can store information for hundreds of years, and magnetic media for decades.

Storage and accumulation are one of the main actions carried out on information and the main means of ensuring its availability for a certain period of time. Currently, the determining direction of the implementation of this operation is the concept of a database, data warehouse (warehouse).

A database can be defined as a collection of interconnected data used by several users and stored with controlled redundancy. The stored data does not depend on user programs; a common control method is used to modify and make changes.

Databank - a system that provides certain services for storing and retrieving data to a specific group of users on a specific topic.

Database system - a set of control system, applied software, databases, operating system and hardware that provide information services to users.

A data warehouse (CD - they also use the terms Data Warehouse, “data warehouse”, “information storage”) is a database that stores data aggregated over many dimensions. The main differences between the database and the database: data aggregation; data from the CD is never deleted; HD replenishment occurs on a periodic basis; the formation of new data aggregates depending on old ones is automatic; access to the CD is based on a multidimensional cube or hypercube.

An alternative to the data warehouse is the concept of data marts (Data Mart). Data marts - a lot of thematic databases containing information related to individual information aspects of the subject area.

Another important area of \u200b\u200bdatabase development is repositories. The simplified repository can be considered simply as a database intended for storing not user but system data. The technology of repositories stems from data dictionaries, which, as they enrich themselves with new functions and capabilities, have acquired the features of a tool for managing metadata.

Each of the participants in the action (user, user group, “physical memory”) has its own idea of \u200b\u200binformation

In relation to users, a three-level representation is used to describe the subject area: conceptual, logical and internal (physical).

Concept levelit is connected with the private presentation of user group data in the form of an external scheme, united by the commonality of the information used. Each specific user works with a part of the database and presents it as an external model. This level is characterized by the variety of models used (entity-relationship model, ER model, Chen model), binary and infological models, semantic networks).

Logic levelis a generalized representation of the data of all users in an abstract form. Three types of models are used: hierarchical, network, and relational.

The structure of basic information technology.

Define the structure and composition of a typical IT. We will call typical ITthe base if it is focused on a specific area of \u200b\u200bapplication. Basic IT creates models, methods of solving problems. Basic IT is created on the basis of basic (standard) hardware and software. Basic IT is subordinated to the main goal - the solution of functional tasks in its subject area (tasks of management, design, scientific experiment, testing, etc.).

At the input of basic IT as a system, a set of tasks is received, for which typical solutions must be found using the methods and tools inherent in IT. Consider the use of basic IT at the conceptual, logical and physical levels.

The conceptual level of basic IT  - The ideology of automated problem solving is set. A typical sequence of problem solving can be represented in the form of an algorithm.

Fig. 2 . The conceptual model of basic IT.

The initial stage is the statement of the problem (PP). If this task is automated control, then it is a set of interconnected algorithms that provide control. PZ - a meaningful description of the problem: the purpose of the task, the economic and mathematical model and method of solving it, the functional and informational relationship with other tasks. It is documented in the teaching materials “Problem Statement and Solution Algorithm”. At this stage, the correctness of the description in terms of criteria is very important.

The next stage is the formalization of the problem (FZ). A mathematical model is being developed.

If the mathematical model is installed, the next step is the algorithmization of the problem (AZ). An algorithm is the process of converting source data to the desired result in a finite number of steps.

The implementation of the algorithm on the basis of specific computing means is carried out at the stage of programming the problem - PRZ. This is a voluminous task, but it is usually carried out using standard programming technologies.

If there is a program, a RH is carried out - solving problems - obtaining specific results for the input data and accepted restrictions.

Stage AR - decision analysis. When analyzing the solution, you can refine the model of formalizing tasks.

The most complex, creative and voluminous are the stages of the formulation of the problem and its formalization. The concept of the initial task is a deep understanding of processes in the subject area.

In the context of basic IT, the global challenge is the development of a domain model (IGO).

When implementing IT, they often encounter poorly formalized tasks. This is where expert systems come to the rescue. The basis of ES is laid the knowledge of the best experts in the subject area. An ES developer collects all known methods of formalizing this task. The user - the developer of this IT - receives options for solving problems. This is an IT design automation process.

The logical level of IT creation. Core IT Models

At a logical level, they establish models for solving the problem and organizing information processes. If the general management model of some ACS is known, in which basic IT will be implemented, we can imagine the relationship between the models of basic IT.

The goal of basic IT at the logical level is to build a model of the problem to be solved and its implementation based on the organization of information processes.

Consider the relationship of basic IT models in the diagram.

Fig. 3 . The logical level of basic IT. A model for organizing information processes.

The model for solving the problem in the conditions of the selected basic IT is consistent with the model of organization of information processes (MOIP). MOIP includes MOU (data processing model), MO (data exchange model), MUPD (data management model), MND (data storage model), MPZ (knowledge representation model). Each of these models reflects certain information processes and contains the bases for constructing private matmodels of a specific information process.

Sharing model   - estimates the probability-time characteristics of the exchange process, taking into account routing (M), switching (K) and transmission (P) of information. The following are involved as impacts: input (message flows); interfering (error streams), and control (control streams). Based on this model, a data exchange system is synthesized, that is, they select the network technology, the method of optimal switching, routing.

MND data storage model.Defines the scheme of the information base of the NIB, establishes the logical organization of information arrays of AMI, sets the physical placement of information arrays of RIM

Information array  - the basic concept, the main element of the machine information support. IM - a collection of data on a group of homogeneous objects containing the same set of information. IM may include information:

• oS programs and test programs (ensure computer operation);
• application programs (provide a solution to a set of functional tasks);
• library of standard programs.

Types of information arrays:

• permanent (formed before the start of the system - directive, reference, regulatory data - not changeable over time);
• intermediate (arise as a result of the previous calculation and the basis for the next);
• current (contain working information about the state of the managed object);
• service (serve the rest of the arrays);
• auxiliary (occur during operations on the main arrays).

By type of carrier, IMs are divided into arrays on machine (internal and external) and non-machine media.

A specific feature of MI is its structure, a way of organizing data by key features. Records can be sorted in ascending or descending order by the value of a key attribute. The most common symptom is chosen as the key one.

MOD data processing model.It determines the organization of the computing processes of the ORP for solving user problems. The sequence and procedures for solving computational problems must be optimized in terms of criteria: memory size, resources, number of calls, etc. The organization of the process directly depends on the subject area. When developing basic IT, you should first choose the right OS. It is the OS that sets the real possibilities for managing the computing process.

The structure of the computing process is determined by the number of tasks. Very important are the requirements for the moment of launch and release (output of results) of tasks. These moments determine the dynamics of obtaining results, that is, the dynamics of the entire process of production management.

The first OS was focused on batch processing of information. This mode, in principle, is not suitable for control tasks of large dimension and efficiency. The transition to time-sharing systems made it possible to give priority to priority tasks under interruption conditions. It turned out to be possible to plan the computing process.

New features for the user are embedded in virtual OSs. It allowed the user to have an unlimited computing resource without noticing the work of neighboring users. In the conditions of distributed data processing, new requirements arise for the computing process. It is required not only to distribute the computing resource between users and their computing tasks, but also to take into account the topology of users.

When creating models for organizing a computing process (ORP), two possible approaches are used: deterministic and probabilistic. In the deterministic approach, the theory of scheduling the sequence of tasks under the imposed restrictions is applied. Unfortunately, random noise interferes with this convenient method. Unforeseen tasks may arise that require urgent solutions. Additional time intervals are allocated for them. With a probabilistic approach, it establishes the average computing resource, the average execution time of the program, and the average performance of the computing system. The averaged parameters are calculated based on statistical data and are constantly adjusted.

If we are inclined to typify the computational tasks to be solved for a particular IT, then the development of application software packages (PPP) is very important.

Among data processing models, simulation models should also be mentioned. With their help, the tasks of planning the organization of the computing process are solved.

Model of knowledge representationKnowledge representation models are the basis for the automated solution of management problems. Knowledge representation models exist in the form of logical A, algorithmic A, semantic C, frame F and integral AND representations.

Data Management Model.Data management - management of the processes of accumulation, exchange and processing of data. The accumulation of data now takes place in the conditions of modern data bases, while the control action should be provided by the input of information, updating it, placing arrays in the database. These functions are performed by a modern DBMS.

With the advent of computers, data was accumulated as a set of identically constructed records - files. When solving each new task, new files were created. There was no logical connection between the files. There was a data integrity problem. A separate program was created for each file access. Individual data in the files were duplicated. The improvement of computer technology and the simultaneous growth of information volumes led to the emergence of the concept of databases. In the database, records are interconnected, can be shared to solve all new tasks.

Depending on the tasks to be solved, database models are selected.

Modern production solves a huge number of routine information tasks. But a very large number of tasks requiring information to make a decision. This requires new approaches to data formation, input and output, processing. These new approaches are being implemented with the help of new IT, realizing their mutual organization. This organization is in charge of a data management model. The model is based on the fact that the data are relatively stable. The stability of the data structure makes it possible to build databases with a stable structure. And the received information should be displayed in the form of variable data values \u200b\u200bin this stable structure.

In accordance with the domain model, a data class can be generated for all tasks to be solved. At the logical level, the subject database includes logical records, their elements and the relationship between them.

Network model it is a model of connection objects that allows only binary many-to-one relationships and uses a model of oriented graphs to describe it.

Hierarchical modelis a kind of network, which is a collection of trees (forest).

Relational modeluses the presentation of data in the form of tables (relations), it is based on the mathematical concept of the set-theoretic relationship, it is based on relational algebra and theory of relations.

Physical (internal) levelassociated with the method of actual storage of data in the physical memory of a computer. It is largely determined by the specific management method. The main components of the physical layer are stored records, combined in blocks; pointers needed to find data; overflow data; gaps between blocks; service information.

According to the most characteristic features of the database can be classified as follows:

by the method of information storage:

• integrated;
• distributed;

by user type:

• single-user;
• multi-user;

by the nature of the use of data:

• applied;
• subject matter.

Currently, there are two approaches to designing a database. The first of them is based on data stability, which provides the greatest flexibility and adaptability to the applications used. The application of this approach is advisable in cases where there are no stringent requirements on the efficiency of functioning (memory size and search duration), there are a large number of diverse tasks with variable and unpredictable queries.

The second approach is based on the stability of the procedures for querying the database and is preferable under stringent requirements for operational efficiency, especially with regard to performance.

Another important aspect of database design is the problem of data integration and distribution. Until recently, the concept of data integration, with a sharp increase in its volume, prevailed until recently. This fact, as well as an increase in the amount of memory of external storage devices when they are cheaper, the widespread introduction of data networks contributed to the implementation of distributed databases. The distribution of data at the place of their use can be carried out in various ways:

1. The copied data. Identical copies of data are stored in various places of use, as it is cheaper than data transfer. Data modification is controlled centrally;
2. Subset of data. Data groups compatible with the source database are stored separately for local processing;
3. Reorganized data. Data in the system is integrated when transferred to a higher level;
4. Partitioned Data. Different objects use the same structures, but store different data;
5. Data with a separate subcircuit. Different objects use different data structures that are integrated into an integrated system;
6. Incompatible data. Independent databases designed without coordination, requiring consolidation.

An important influence on the process of creating a database is provided by the internal content of the information. There are two directions:

• application databases focused on specific applications, for example, a database can be created to record and control the receipt of materials;
• subject databases focused on a particular data class, for example, the subject database “Materials”, which can be used for various applications.

The specific implementation of the database system on the one hand is determined by the specifics of the data of the subject area, reflected in the conceptual model, and on the other hand, by the type of specific DBMS (MDB) that establishes the logical and physical organization.

To work with the database, a special generalized toolkit is used in the form of a DBMS (DBM), designed to manage the database and provide a user interface.

Main DBMS standards:

• data independence at the conceptual, logical, physical levels;
• universality (in relation to the conceptual and logical levels, type of computer);
• compatibility, redundancy;
• data security and integrity;
• relevance and manageability.

There are two main areas of DBMS implementation: software and hardware.

A software implementation (hereinafter referred to as a DBMS) is a set of software modules that runs under the control of a specific OS and performs the following functions:

• data description on conceptual and logical levels;
• data loading;
• data storage;
• search and response to a request (transaction);
• alteration;
• ensuring security and integrity.

Provides the user with the following language tools:

• data description language (YaD);
• data manipulation language (NMD);
• applied (built-in) data language (FAN, VND).

The hardware implementation involves the use of so-called database machines (MDBs). Their appearance is caused by increased volumes of information and access speed requirements. The word “machine” in the term MBD means an auxiliary peripheral processor. The term "database computer" is a stand-alone database processor or a processor that supports a DBMS.

The main directions of the MDB:

• parallel processing;
• distributed logic;
• associative memory;
• conveyor memory;
• data filters, etc.

The set of database design procedures can be combined in four stages. On stageformulation and analysis of requirementsset the goals of the organization, determine the requirements for the database. These requirements are documented in a form that is accessible to the end user and the database designer. Usually, the method of interviewing personnel at various levels of management is used.

Stage conceptual designconsists in the description and synthesis of information requirements of users in the initial design of the database. The result of this step is a high-level presentation of user information requirements based on various approaches.

In the process logical designhigh-level data representation is transformed in the structure of the used DBMS. Received logical structure  A database can be quantified using various characteristics (the number of calls to logical records, the amount of data in each application, the total amount of data, etc.). Based on these assessments, the logical structure can be improved in order to achieve greater efficiency.

On stage physical designissues related to system performance are resolved, data storage structures and access methods are determined.

The entire database design process is iterative, with each stage being considered as a set of iterative procedures, as a result of which they get the corresponding model.

The interaction between the design stages and the vocabulary system needs to be considered separately. Design procedures can be used independently in the absence of a vocabulary system. The dictionary system itself can be considered as an element of design automation.

The stage of dividing the database is related to dividing it into sections and the synthesis of various applications based on the model. The main factors determining the partitioning technique are: the size of each section (permissible sizes); application usage patterns and frequencies; structural compatibility; database performance factors. The relationship between the database partition and applications is characterized by an application type identifier, a host identifier, the frequency of application use and its model.

Application models can be classified as follows:

1. Applications using a single file.
2. Applications that use multiple files, including:

Allowing independent parallel processing;

Allow synchronized processing.

The complexity of the implementation phase of the database is determined by multivariance. Therefore, in practice, it is recommended first of all to consider the possibility of using certain assumptions that simplify the DBMS functions, for example, the admissibility of temporary DB mismatch, the implementation of the database update procedure from one node, etc. Such assumptions have a great influence on the choice of the DBMS and the considered design phase.

Design tools and evaluation criteria are used at all stages of development. Any design method (analytical, heuristic, procedural) implemented in the form of a program becomes a design tool that is practically not affected by the design style.

Currently, the uncertainty in choosing criteria is the weakest point in database design. This is due to the difficulty of describing and identifying an infinite number of alternative solutions. It should be borne in mind that there are many signs of optimality that are immeasurable; it is difficult for them to quantify or present them as an objective function. Therefore, the evaluation criteria are usually divided into quantitative and qualitative. The most commonly used criteria for evaluating a database, grouped into such categories, are presented below.

Quantitative criteria: the time required to answer the question, the cost of modification, the cost of memory, the time to create, the cost of reorganization.

Qualitative criteria: flexibility, adaptability, accessibility for new users, compatibility with other systems, the ability to convert to another computing environment, the ability to restore, the possibility of distribution and expansion.

The difficulty in evaluating design decisions is also associated with different sensitivity and duration of the criteria. For example, an efficiency criterion is usually short-term and extremely sensitive to ongoing changes, and concepts such as adaptability and convertibility manifest themselves over long time intervals and are less sensitive to environmental influences.

The purpose of the data warehouse is information support for decision making, rather than operational data processing. Therefore, the database and the data warehouse are not the same concepts.

The main functions of the repositories:

• on / off paradigm and some formal procedures for objects;
• support for multiple versions of objects and configuration management procedures for objects;
• notification of instrumental and working systems of events of interest to them;
• context management and various ways of viewing repository objects;
• definition of workflows.

Let us briefly consider the main directions of scientific research in the field of databases:

• development of the theory of relational databases;
• data modeling and development specific models  various purposes;
• mapping data models aimed at creating methods for their transformation and constructing commutative mappings, developing architectural aspects of mapping data models and specifications for determining mappings for specific data models;
• creation of a DBMS with a multimodel external level, providing the ability to display widespread models;
• development, selection and evaluation of access methods;
• creation of self-describing databases that allow applying uniform access methods for data and metadata;
• concurrent access management;
• development of a database and knowledge programming system that would provide a single effective environment for both application development and data management;
• improving the database machine;
• development of deductive databases based on the use of mathematical logic and logical programming tools, as well as spatio-temporal databases;
• integration of heterogeneous information resources.

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	Especially a person in this folding organisation takes a central nervous system in one function in one of all the fabrics and organisms. Dyakuyuchi great number of low-level receptors of the central nervous system sprimaє bagatochnyh zmіni shchinut in the call of the environment and the whole body and the big role in the regulation of all the side of the world’s health. The process of behaving in the central nervous system lies in the basis of mental activity and human behavior. The central nervous system’s activity is called coordinating, but it’s Uzgodzhuvalnoy.
22571.		Spinal cord	49.5 KB
	There is a segmental organ: in humans, there are 31 pairs of spinal cord roots in the toad; 10 in the skin segment; in the skin segment, two parts: the anterior ventral and posterior dorsal roots. Syra cilia of the spinal cord on the transverse abrasion of the metelica panicle abliteri N. Є also dorsal horns of the spinal cord with the ventral wide fusion of the cirrhosis of the spinal cord. .

Before defining a convenient storage method for yourself, you need to answer a few simple questions, which we will talk about below.

Simple ways for every day

The easiest option that is available at any time to every PC owner is to store all the information on a computer. The advantages of this solution are obvious:

• Cheap - no need to splurge on assistive devices.
• Speed \u200b\u200b- saving information on a computer is very fast.
• Simplicity - while working on a computer, just one “Save” button is enough.

This method is convenient when you need to quickly create a copy of the brought information for subsequent sorting. However, this solution also has disadvantages:

• Lack of mobility - even if you have a laptop, you are unlikely to carry it everywhere with you, which means that information is losing its availability. Here's the first question: will stored information be needed outside the computer? Tablet owners have other problems: the battery runs out at the most inopportune moment.
• Reliability - a computer’s hard drive rarely crashes, but in this case, the restoration of stored information will be very expensive. In addition, it is possible to format the disk.

The next fairly common way is to store information on a DVD or CD. Such a solution is quite mobile and reliable (it is believed that DVD disc capable of storing data up to 120 years), and even accidentally erasing information will not work. Although, in real conditions  retrieving data even after 10 years is already quite difficult. On this, the pros end and the cons begin:

• Simplicity - to record information, you need to spend much more effort, and sometimes install additional programs.
• Compactness - over time, the recorded discs will occupy a very large area, and you will need to organize additional space for them.
• Speed \u200b\u200b- writing to the "blank" is a rather lengthy process, and information is not read from it right away.
• Cost - the price of 1 disk is not so high, but all data will not fit on 1 disk. In addition, it is recommended that for security reasons, periodically overwrite discs with important files.

Of the unobvious advantages of such a solution is the convenience of storing certain media files. For example, slide shows with your favorite photos, video recordings from various events, or collections of your favorite music. Hence the following two questions:

1. Will the information need to be changed?
2. Type of information to save.

The next storage method is the most common. These are various flash drives, including SD cards. Pros:

The disadvantages include:

• Reliability - flash drives not only burn out, but also easily become infected with viruses. In addition, they are often simply lost and files from them are easy to delete by accident.
• Price - the cost of drives is relatively low, but one flash drive may not be enough.

Family archive or long-term storage option

The next method concerns rather long-term storage of information and answers the question of where to store large-volume information. These are external hard drives or network attached storage. They come in different sizes and are generally quite compact, some fit in the body of a conventional flash drive. The read / write speed depends on the characteristics, but is faster than on a DVD. In addition, a lot of information fits, due to the large volume. The only drawback is the high price, but taking into account durability and all the advantages, it is quite justified.

Network storage is an interesting option with the ability to organize access to information for several people. This is a fairly compact format, and if necessary, it is easy to remove the necessary hard drive from there, so there will be no problems with mobility either. And in case of a lack of space, you can always add an additional hard drive.

The next method is for advanced users, since not everyone can bring it to life on their own. This is a server with a file storage function.

Physical drives

To summarize: what are the storage media and their characteristics?

1. Computer hard drive (capacity from 80 GB);
2. CD / DVD-ROM (from 700 MB);
3. external hard drive (from 16 GB);
4. Flash drive and memory card (from 1 GB).

In addition to the volume, when choosing devices, you need to pay attention to the read / write speed.

Internet data storage

Now let's talk a little about the opportunities that the Network gives us. Where to store information on the Internet? There are two options: cloud services and file sharing. Both of them work both for free and for an additional fee, providing more volume or speed.

File hosting appeared a long time ago. Information can be stored there, but not always reliably. Although data is stored on servers, such services are designed more for file sharing, and this imposes a limitation on the storage period. And, returning in a month, you risk not finding your data via the link. But it’s very convenient to share small files with friends and colleagues.

Another thing - cloud storage. Now almost all the major services work on cloud technologies: Dropbox, Yandex-drive, Google-drive. Each user is provided with a small disk space, access to which is from any computer. Working with files is very convenient, because synchronization is most often automatic, and some services allow several users to work on a single document at the same time.

The issue with compactness is also not worth it, because you do not have a physical drive. This method is very reliable, and the speed depends only on the speed of your Internet channel. This is where the biggest drawback of cloud technologies lies: no Internet - no data. Or there is, but then they will take up space on the hard drive, and this is not always convenient.

Another convenient way to store data is Evernote. It is not suitable for storing large amounts of data, but it is very convenient to store notes with interesting materials from the Internet in it. And it can also be used as an organizer. Information will be safely stored in the clouds, but will be available without the Internet, thanks to synchronization with the hard drive.

So, it's time to answer the main question: where is the best place to store information? Best in several places at once. For example, on a flash drive and on a computer, on external hard drive and in the clouds, on floppy disks, and in network attached storage. And some files can be additionally printed: for example, important documents or favorite photos.

Audio and Video editors introduced you to the main ways of storing information, we hope the article was useful to you. Now tell me, please, how do you store your important files?

January 11th
17:36

Information storage is a topic that has been relevant since the days of cave painting. In an era of rapid technological progress and a variety of proposals, it becomes even more difficult to find a definitely better solution. Depending on the amount of information (data center or PC ordinary user), the range of solutions is radically different. It’s already time to write textbooks and scientific treatises about data storage at the data center architecture level, while at the user level you can still limit yourself to a more or less concise answer. The user should approach the issue of storing information already with an understanding of how often it will be in demand and what is the degree of its confidentiality.

Immediately it is worth noting that one cannot completely trust one of the storage methods 100%, as well as laying eggs in one basket. You should use several methods at once, among which it is worth highlighting backups - without them, nowhere. Further, you can consider certain scenarios.

If we are talking about very important information, access to which is not required every day, then the most radical solution would be to use an optical disk stored in a fireproof safe. Of course, this method also has its drawbacks: prevalence optical drives  today it’s falling, and if you need to transfer data, you won’t take it far.

In situations where privacy is important, a DataTraveler 2000 (DT2000) encrypted USB drive can help out. Its main advantage is the ability to encrypt data on the fly, after which access to it without a password becomes impossible. Even with the loss of media, after 10 attempts to enter a password, the drive is automatically erased. Kingston offers a large number of  similar devices, a list of which can be found on the manufacturer’s website.

Otherwise, you should act when it comes to everyday use information. Usually this is a set of work programs, games, audio and video content. Most often, such information is stored on the HDD or SSD installed in the user's PC. Today the benefits of ordinary hard drives Before SSD, in terms of unit prices, they are no longer so pronounced, and in terms of write / read speed and response time, HDDs are ten times inferior. It is worth mentioning the reliability, which is much higher with SSDs today - their fault tolerance has long equaled that of ordinary hard drives. Do not forget about the "cloud" solutions, because part of the important content can be trusted network resources. In order to minimize the risks of information getting to third parties, I recommend encrypting the content that is contained on the PC. For this, the operating system itself already has all the necessary tools: for Windows it is BitLocker, for Mac OS - FileVault.

Information on mobile devices  usually stored on SD or microSD cards. The assortment of such products is unlimited, but it is better to give preference to brands already established in this market. The great popularity of individual brands is explained by an increased level of quality control, because a small manufacturer, for the sake of a low price, may forget about reliability. Kingston has besides cards with different speed  There is also a very interesting solution for recordings - cards that meet industry standards for working in extreme conditions. They are based on MLC chips and can be used over a wide temperature range. Actual solution for those who are interested in increased reliability of the information carrier.

Task reserve copy  information on mobile devices can be solved using the "cloud" services or by connecting to a PC. But I want to note the tools available on sale that make backup even easier. Probably the most popular solution for gadgets based on Android OS can be a DataTraveler MicroDuo flash drive (DTDUO) with support for the OTG function. This is a drive with two connectors: on one end they have USB Type-A, on the other - microUSB or USB type-C. A very convenient solution for field conditions, when you urgently need to drop information or the memory on your smartphone / tablet is not enough. For gadgets based on iOS and others, Kingston has a more radical solution - the MobileLite Wireless G3 wireless card reader. Using a wireless connection, you can easily and easily transfer the necessary data to any USB-drive or SD card. The same method will be relevant for photo / video equipment.

Complain

January 11th
17:42

You need to start with the fact that there is no absolutely reliable way to store data, any system and any device can break. The question here is more likely not whether this will happen or not, but when it will happen and whether you will be ready for it. Our Backblaze colleagues have compiled and published interesting usage statistics. disk drives  in their servers. It turned out that, depending on the manufacturer, from 2% to 8% of disk drives break down in a year of operation.

In addition, data loss can occur not only due to a program crash or device failure, there are many other reasons, such as hacking, an ransomware attack, or just a human factor, such as deleting data by mistake. For example, many experts call 2016 the year of ransomware. In the first half of the year alone, more than 7 million different ransomware programs were discovered, and the annual growth of users affected by these programs was 500%.

Cloud data warehouses, as a rule, have a built-in data protection system, but even they cannot guarantee 100% data security.

Registration and storage of information originates from images carved on stone in the Neolithic and Bronze Age. Centuries passed, until writing came to man, and then typography.

Only in the XIX century. photography was invented (1839) and cinema (1895). These two remarkable inventions made it possible to register and store information in the form of images and sound.

An interesting way of storing discrete information was proposed by the French mechanic J. Vacanson, who created a software-controlled loom in 1741. To memorize the program, he used a mechanical perforated drum. Only 60 years later, the drum was replaced by perforated cardboard, which was the prototype of punched cards and punched tapes.

A fundamentally important event was the invention of the recording of electrical signals on magnetic tape, which laid the foundation for many varieties of magnetic recording devices. The production of magnetic tape began relatively recently in 1928, although the principle of recording sound using a magnetic field has been known for over a hundred years.

We have already said that the computer memory is divided into operational and long-term (permanent) by the nature of access to it and the amount of information stored in it. The central processor of the computer accesses random access memory at any time, reading and writing information in the RAM occurs quickly, at the pace of the computer. The computer records large amounts of information into long-term memory and accesses it occasionally.

The difference between operational and long-term memory is the access time to the memory, so often instead of these names they use their physical implementation - semiconductor and magnetic memory, but now there are prerequisites for creating a large-capacity memory device and at the same time with quick access, low price and size.

The computer operates with two characters: yes (1) and no (0). The yes and no states are physically realized in an electrical relay that has two stable states. At the time, the relay was replaced by an electronic lamp, and then a transistor. The memory device on lamps or transistors is implemented in a "trigger" circuit, which has two stable states, therefore, it is able to store the values \u200b\u200b0 and 1. Various physical principles are used to perform this operation. A trigger (trigger means a trigger, a latch) is an "electronic relay", which, like an electric relay, can be in one of two possible states, expressed by different voltages at a selected point in the circuit. One voltage is conditionally taken as 0, the other as 1. The trigger retains one of the two stable states for an arbitrarily long time and jumps from one state to the other under the influence of an external signal.

To remember one bit of information, one trigger is needed. By connecting several triggers in series, you can get a device for storing binary large numbers, and each previous trigger will serve as a signal source for the subsequent one. A set of triggers designed to store a binary number of a certain length is called a register. It should be noted that such a memory device only works when the power is on.

If access to memory cells (triggers) is organized so that the writing and reading of binary information is performed simultaneously at all cells, the memory device is called random access memory. If the register is made so that the information in it is transmitted sequentially from the previous cell to the next, it is called a shift register or a device with serial memory.

The computer’s RAM can consist of many trigger elements of any nature. In the years of the existence of computers, fundamentally developed and technically implemented different devices  RAM, although some of them are currently only found in museums. They are implemented on the simplest semiconductor structures, based on cryogenic elements, cathode ray tubes, cylindrical magnetic domains, holography, using complex molecular and biological systems.

Below we will consider some devices of operational and long-term memory, created on various physical principles and at different periods of the development of computer technology.

Memory on ferrite cores.  Ferrite is a semiconductor magnetic material made from powdered oxides. Ferrite has strongly pronounced magnetic properties with an almost rectangular hysteresis loop (dependence of magnetic induction on magnetic field strength).

A magnetic core with a rectangular hysteresis loop is a good element for storing information in binary code. It can be agreed that the magnetized state of the core corresponds to 1, and the demagnetized state 0. The transition from one state to another occurs under the influence of current in the coil. A ring of ferrite material with windings behaves similarly. To control the magnetic state, there must be appropriate write and read windings on the ring. The reading of information is based on the above effect: if the core under the influence of the pulse remained in the same state, then 1 was written in it, if the core passed another state under the influence of a pulse of opposite polarity, it recorded 0.

From a set of ferrite rings, a memory matrix is \u200b\u200bassembled in which each element is in the 0 or 1 state, and as a result, as many bits are stored as in the matrix of rings. The matrix is \u200b\u200bformed by a grid of horizontal and vertical wires (tires), at the intersection of which ferrite rings are placed. With the help of tires, the magnetic state of each ring is controlled.

To reduce the overall dimensions of the memory device, the dimensions of ferrite rings are minimized. The outer diameter of the elbows is 0.45 mm; the switching time is 30 ns. The miniaturization of a ferrite storage device, unfortunately, has a limit due to the inner diameter of the ferrite ring. So, a ring with a diameter of 0.3 mm is very difficult to pass through several conductors without breaking it.

Ferrite series storage devices have capacities up to 20 Mbps.

Memory on cylindrical magnetic domains.  The basis of this type of device is the following physical effect: in some magnetic materials, when exposed to an external magnetic field, separate regions may arise that differ from the rest of the material in the direction of magnetization. These areas are called "domains" (domain managed area, district). Under the influence of a weak external magnetic field, domains can move in a plate of ferromagnetic material in predetermined directions at a high speed. This domain transfer feature allows you to create storage devices. A good domain-forming material is a ferrite garnet film.

Domain structures can be strip, ring, cylindrical. Devices on cylindrical magnetic domains (DML) are a new step in the application of magnetism in the technique of storage devices.

The information carriers in such a device are isolated magnetized portions of magnetic crystals. The domain size is from 0.01 to 0.1 mm, so several million domains can be placed on one square centimeter of material. The domains observed under the microscope have the shape of bubbles, hence the English version of the name of this type of memory - magnetic bubble memory (magnetic bubble memory).

Domains can be generated or destroyed, their movement allows you to create logical operations, because the presence or absence of a domain at a certain point in the magnetic crystal can be considered as 1 or 0.

It is very important that when disconnected, the domains are saved.

Semiconductor modules - chips (chip - a thin piece of wood or stone) are produced on the basis of a domain-containing crystal. For the formation of cylindrical domains in the chip, it is placed in constant and rotating magnetic fields formed by a permanent magnet and an electromagnet.

A domain register consists of a domain input device (domain generator), output (resistive sensor), and permalloy film. Domains are generated by directly generating domains at one point or another in the crystal. The generation and input of domains into the shift register is performed by a conductive loop from a permalloy film. When a current appears in the generator, a local magnetic field is created. Under the influence of this field, a domain is generated in the region bounded by the loop contour, which then takes a cylindrical shape under the action of a constant displacement field. In this formed form, the domain enters the shift register.

One chip can store up to 150 bits, and the entire drive is 10 Mbps. There were 16 Mb drives. A storage device of such capacity has the dimensions of a small suitcase.

The information in the chip is read on cylindrical magnetic domains using magnetoresistive permalloy sensors or Hall sensors. Under the influence of the magnetic field of the domain, a change in electrical resistance occurs in the permalloy film, or an electromotive force arises in the semiconductor sensor under the influence of the domain.

Semiconductor memory.  To memorize electrical signals, semiconductor structures are used, on the basis of which bipolar transistors, MOS transistors (metal-oxide semiconductors), MNOS transistors (metal-nitride-oxide semiconductors) and charge-coupled devices (CCDs) are created.

The memory blocks on transistors are organized similarly to memory blocks on ferrite cores. The main disadvantage of semiconductor memory should be considered significant power consumption and loss of information during a power outage.

The bipolar transistor is a device with two p-n junctions. Under the action of the base - collector voltage, the state of the transistor changes: it can be open or locked. These states are used as 0 and 1.

A metal oxide chip transistor is a type of field effect transistor. The name of this transistor comes from three components: a metal gate, a layer of insulating oxide and a semiconductor substrate. It is a semiconductor device in which the resistance between its two terminals is controlled by the potential supplied to the third terminal (gate). Under the influence of the control voltage, the MOS transistor can be in closed or open states.

On bipolar transistors, field MOS and MNOS transistors, CCDs collect integrated storage devices.

The manufacturing technology of semiconductor structures allows you to create integrated storage devices based on them. The basis of all semiconductor elements is a silicon wafer, on which the entire logical memory block is assembled. So, one storage unit on the MOS structure is a matrix of 256 storage elements.

Of the devices mentioned by us, CCDs are considered new page  in the development of microelectronics, experts predict the future for them and believe that they can be better than storage devices on cylindrical magnetic domains and medium-sized magnetic disks.

Memory on cathode ray tubes (CRT).  A cathode ray tube without a phosphor coating can serve as a storage device. The electron beam, acting on the glass of the flask, leaves on it electric charge, and this charge persists for a long time, since glass is a good dielectric. The charge is also read by an electron beam, the movement of which is controlled by deflecting plates. The presence of charge on the target is judged by the change in the beam current.

The technology allowed for highly efficient CRT memory. So, instead of glass, an electrostatic silicon matrix is \u200b\u200bused, consisting of many microcapacitors having a transverse size of about 6 microns.

The target of the tube on the MOS structure stores information in the form of a potential relief, which is formed in the oxide layer of the plate. When recording at the point of contact between the beam and the target, a charge accumulates, which corresponds to 1. absence of charge 0. A CRT performed on this principle has a capacity of 4.2 Mbit with a target area of \u200b\u200b1 cm2.

Tape memory.  Recording information on magnetic tape is based on the principle of retaining residual ferromagnetic materials
magnetization corresponding to the magnetic field when recording. A magnetic tape is a storage medium in the form of a flexible plastic tape coated with a thin (0.01-10 μm) magnetic layer. The tape moves at a uniform speed past the magnetic head, and its surface is magnetized depending on the instantaneous value of the magnetic field created by the head in accordance with the signal arriving at it.

When a magnetic tape is passed by a reproducing head, an electromotive force corresponding to the degree of magnetization of the magnetic layer of the tape is induced in its winding. This principle of recording and playback is the same for magnetic drums and discs.

Modern high-capacity magnetic tape storage devices
  relatively cheap and compact, ways to store information for a long time. They allow multiple reading and insertion. new information, to the place previously recorded.

Digital information can be recorded on magnetic tape on several parallel tracks, with each track having its own recording-playback head or one team head moves to the desired track.

In storage devices on magnetic tape, information blocks are placed (recorded) at intervals sufficient to stop the tape drive mechanism. Each information block has its own address in the form of a code word. A large block of information is sampled from the tape by comparing the address of the block stored in the computer's memory register with that read from the tape; current numbers (addresses) of blocks.

The main drawback of tape memory is considerable time
sampling information. But such a memory has a good amount of stored information - 40 GB with a very compact size.

Memory on magnetic drums and disks.  The main element of a magnetic drum memory device is the drum itself, coated with magnetic material. A number of heads are installed at the surface of the drum for non-contact recording and reading. For example, a drum may have 278 tracks that are served by 24 heads. The rotation of the drum occurs at a frequency of about 20 thousand revolutions per minute, as a result of which the speed of information retrieval can be several tens of milliseconds.

A magnetic drum memory device is extremely mechanically accurate. To increase its reliability, the heads are sealed, creating automatic system floating heads when a constant clearance of about 5 microns is maintained between the surface of the drum and the head.

A competitor to a magnetic drum is a magnetic memory device
  disks, which appeared in the early 60s after the development of the production of floating magnetic heads on an air cushion. The increase in the surface used to record information on magnetic disks  compared with
magnetic drums, allowed at the same recording density to develop devices with capacities that exceed the capacity of devices on magnetic drums many times, so the magnetic drums were completely replaced by magnetic disks.

Regardless of the size of the disk, the drive consists of three physical nodes: a cassette with a disk, a disk drive and an electronic part.

Hard drives are made of aluminum or brass, they can be permanently installed and removable; information is recorded on the magnetic layer along concentric tracks; standard diameters 88.9; 133.35 mm, thickness about 2 mm; both surfaces are working. The disk is mounted on a shaft that is driven by an electric motor. The gap between the surface of the disk and the magnetic head is 2.5-5.0 microns and should be kept constant during operation. To this end, they thoroughly process the surface of the disk and use special aerostatic type heads floating above the disk. The heads for writing and reading are moved in the gap between the disks with the help of a support controlled by a servo special commands.

The average capacity of a track is quite large (approximately 40 Kbytes), so each track is divided into sectors for faster search. With the hardware division of the disk into sectors on the inner circle there are 32 holes marking the beginning of the sectors.

The disk capacity can reach hundreds of Gbps, and the access time to the information block is from 1 to 10 ms.

The main advantage of disk storage is relatively quick search  the necessary information block and the ability to change disks, which allows you to read data recorded on another computer from the disks.

For mini and microcomputers are widely used hard disks  (Seagate, IBM, Quantum). The peculiarity of hard drives is the sealing of media, which allows to reduce the gaps between the heads and the disk, significantly increase the recording density. Sealing also increases the reliability of the device.

Information storage on microfilm.  Strange as it may seem,
but information can also be stored on microfilms. With an A6 film size, it is capable of storing about 1 MB of information.

Microfilming is based on the principle of photography. The creation of the first microform dates back to 1850. For a long time, 35- or 16-mm roll film was used for microfilming. Unlike conventional microfilming, microfiche is a photographic recording of information on a flat photographic film of standard size A6 105x148 mm. The image of a regular A4 text page (296x210 mm) is reduced by optics by 24 times and is fixed on the microfiche in the form of a small cell.

In total, on the microfiche 105x148 mm, 98 reduced images of ordinary pages of text are placed.

It is possible to use a system with a resolution that allows you to place 208 or 270 page images on a microfiche. The most widely used reduction ratios are 21, 22, and 24.

The idea of \u200b\u200bmicrofilms is widespread, as it allows
carry out compact paperless storage of any documents. Microfilming is especially widely used by patent offices, scientific and technical libraries, government agencies and banks. So, in 1989 in the United States, up to 30% of all microfiches were used by government agencies. And before the beginning of 1984, the volume of information stored in the archives of the United States amounted to 21 billion pages of text, a significant part of which is recorded on microfiche.

Microfiches are stored in special boxes of 15 pieces each. Klyassers are placed in boxes. For comparison, we say that the Journal of the American Chemical Society from 1879 to 1972. it is stored on shelves 18 m long, and the same microfiche magazine in boxes occupies a 1.65 m long shelf. Thanks to the developed special ordinal systematics, the search for necessary information is possible by conventional (manual) methods and using a computer. Visually readable designations of the serial number and the header field allow you to quickly find the necessary microfiche, and then the necessary pages of text.

Depending on the type and size of the microfiche storage, various search tools can be used: edge perforation cards, superposition cards, machine sorted punched cards, or computer searches.

It is clear that in the processes of microfiche and the reproduction of information on paper, the carrier — film — plays a fundamental role. The first high-resolution electrographic image on a polymer film was obtained in 1962 by Bell & Howell (USA), then the technology was picked up by others and found wide application. Kodak's Ektavolt film has a resolution of 800 lines / mm, resulting in a 100-fold reduction in the size of the original. The original film is Eastman Kodak's film type SO-101 and SO-102, which allows you to transfer the image from the screen of a cathode ray tube to a film with a large reduction.

There are several methods for capturing images on film under computer control. Firstly, it can be a copy in a reduced form of images from the screen of a cathode ray tube. Secondly, the image on photographic film can be applied by electronic or laser beam controlled by a computer. The performance of such a system is extremely high - in one minute the system can "print" about half a million characters.

There are two types of devices for recovering information from microfiche: for reading microfiche with magnification of images from 16 to 26 times, for reading microfiche and at the same time receiving paper copies.

The first type of device is a desktop type enlarger with a projection of images in transmitted or reflected light. The enlarged micro frame is projected onto the table plane or onto the screen. A bright and clear image of 275x390 mm, as is done with the Pentakata Mikrofilmtechnik, allows operation in rooms with normal lighting.

The second type of device, in addition to reading information, allows receiving an enlarged paper copy upon request.

To characterize the equipment for recording and reproducing information using microfiches, we present the composition and data of the equipment of the Swiss company Messerly:

a camera for shooting printed text on microfiche with a productivity of 1500 - 2000 documents per hour (15 microfiche);

developing machine AP-F-ЗО with a productivity of 900 m of film per hour;

microfiche duplication device producing 120 duplicates per hour;

aM 1830 projection magnifying device, fixing images on normal paper, its productivity is 900 copies per hour;

an automatic microfiche search device having a search time of about 3 s;

m-F-4A microfiche image display device.

The use of such equipment can provide significant savings in storage space and personnel, but, in turn, it is an expensive equipment and requires qualified maintenance.

RAM chips.  Of the memory microcircuits (RAM - Random Access Memory, memory with random access) two main types are used: static (SRAM - Static RAM) and dynamic (DRAM - Dynamic RAM).

In static memory, elements (cells) are built on different variants of triggers - circuits with two stable states. After a bit is written to such a cell, it can remain in this state for as long as desired - only the presence of power is necessary. When the static memory is accessed to the microcircuit, a complete address is supplied to it, which, with the help of an internal decoder, is converted to the selection signals of specific cells. Static memory cells have a short operating time (units to tens of nanoseconds), however, microcircuits based on them have a low specific data density (on the order of units of Mbit per case) and high energy consumption. Therefore, static memory is mainly used as a buffer (cache memory).

In dynamic memory, cells are constructed on the basis of areas with accumulation of charges, occupying a much smaller area than triggers, and practically not consuming energy during storage. When a bit is written to such a cell, an electric charge is formed in it, which is stored for several milliseconds; to permanently save the charge of the cell, you need to regenerate - rewrite the contents to restore the charges. The cells of the dynamic memory microcircuits are organized in the form of a rectangular (usually square) matrix; When accessing the microcircuit, its inputs are first supplied with the address of the matrix line, accompanied by the RAS signal (Row Address Strobe); then, after a while, the address of the column is matched by the CAS signal (Column Address Strobe - column address). Each time the cell is accessed, all the cells of the selected row are regenerated, therefore, to completely regenerate the matrix, it is enough to go through the row addresses. Dynamic memory cells have a longer response time (tens to hundreds of nanoseconds), but a higher specific gravity (of the order of tens of Mbit per case) and less power consumption. Dynamic memory is used as the main one.

The usual types of SRAM and DRAM are also called asynchronous - because setting the address, supplying control signals and reading / writing data can be performed at arbitrary moments of time - it is only necessary to observe the temporal relations between these signals. These temporal relations include the so-called guard intervals necessary for signal stabilization, which do not allow achieving the theoretically possible memory speed. There are also synchronous types of memory that receive an external clock signal, to the pulses of which the moments of addresses and data exchange are rigidly tied; in addition to saving time on secure intervals, they allow more complete use of internal pipelining and block access.

FPM DRAM (Fast Page Mode DRAM - dynamic memory with fast page access) has been actively used in the past few years. The memory with page access differs from ordinary dynamic memory in that after selecting a matrix row and holding the RAS, it allows multiple setting of the address of the column encoded by CAS, as well as quick regeneration according to the "CAS before RAS" scheme. The first allows you to speed up block transfers when the entire data block or part of it is located inside one row of the matrix, called a page in this system, and the second - to reduce the overhead of memory regeneration.

EDO (Extended Data Out) - the extended time for holding the output data) is actually an ordinary FPM chip, at the output of which registers are installed - data latches. For paginated exchanges, such microcircuits operate in a simple pipeline mode: they hold the contents of the last selected cell at the data outputs, while the addresses of the next selectable cell are already fed to their inputs. This makes it possible to speed up the process of reading sequential data arrays by about 15% compared to FPM. With random addressing, such a memory is no different from ordinary memory.

BEDO (Burst EDO - EDO with block access) - EDO-based memory that works not in single, but in batch read / write cycles. Thanks to the internal and external caching of commands and data, modern processors exchange mainly blocks of words with the maximum width with the main memory. In the case of BEDO memory, there is no need to constantly supply consecutive addresses to the inputs of the microcircuits, observing the necessary time delays - it is enough to gate the transition to the next word with a separate signal.

SDRAM (Synchronous DRAM - synchronous dynamic memory) - memory with synchronous access, faster than normal asynchronous (FPM / EDO / BEDO). In addition to the synchronous access method, SDRAM uses the internal separation of the memory array into two independent banks, which allows combining a sample from one bank with setting the address in another bank. SDRAM also supports block sharing. It is expected that in the near future SDRAM will supplant EDO RAM and will occupy a major position in the field of general-purpose computers.

PB SRAM (Pipelined Burst SRAM - static memory with block pipelined access) is a type of synchronous SRAM with internal pipelining, due to which the data exchange rate is approximately doubled.

Memory microcircuits have four main characteristics - type, volume, structure and access time. The type denotes static or dynamic memory, the volume shows the total capacity of the microcircuit, and the structure shows the number of memory cells and the size of each cell. For example, the 28/32-pin SRAM DIP chips have an eight-bit structure (8k * 8, 16k * 8, 32k * 8, 64k * 8, 128k * 8), and the 486 cache for 256 kb will consist of eight 32k * chips 8 or four 64k * 8 microcircuits (this is a data area - additional microcircuits for storing tags (tag) may have a different structure). Two 128k * 8 microcircuits can no longer be delivered, since a 32-bit data bus is needed, which can only give four parallel microcircuits. The distributed PB SRAMs in the 100-pin PQFP packages have a 32-bit 32k * 32 or 64k * 32 structure and are used in two or four in Pentuim boards.

Similarly, 30-pin SIMMs have an 8-bit structure and are installed with two processors 286, 386SX and 486SLC, and four with 386DX, 486DLC and regular 486. 72-pin SIMMs have a 32-bit structure and can be installed from 486 one at a time, and with Pentium and Pentium Pro - two at a time. 168-pin DIMMs have 64-bit structures and are installed in Pentium and Pentium Pro one at a time. Installing memory modules or cache chips in an amount greater than the minimum allows some boards to speed up the work with them using the principle of layering (Interleave - interleaving). The access time characterizes the speed of operation of the microcircuit and is usually indicated in nanoseconds through a dash at the end of the name. On slower dynamic circuits, only the first digits can be indicated (-7 instead of -70, -15 instead of -150), on faster static "-15" or "-20" indicate the real time of access to the cell. Frequently, the minimum of all possible access times is indicated on microcircuits - for example, the distribution of 70 ns EDO DRAM is distributed, like 50, or 60 ns - as 45, although such a cycle is achievable only in the block mode, and in the single mode the microcircuit still works 70 or 60 ns. A similar situation occurs in the marking of PB SRAM: 6 ns instead of 12, and 7 instead of 15.

The following are examples of typical markings of memory microcircuits; the designation usually (but not always) contains the volume in kilobits and / or structure (bit address and data).

Static:

61256 32k * 8 (256 kbps, 32 kb)

62512 64k * 8 (512 kbps, 64 kb)

32C32 32k * 32 (1 Mbps, 128 kb)

32C64 64k * 32 (2 Mbps, 256 kb)

Dynamic:

41256 256k * 1 (256 kbps, 32 kb)

44256, 81C4256 256k * 4 (1 Mbps, 128 kb)

411000, 81C1000 1M * 1 (1 Mbps, 128 kb)

441000, 814400 1M * 4 (4 Mbps, 512 kb)

41C4000 4M * 4, (16 Mbps, 2 Mb)

MT4C16257 256k * 16 (4 Mbps, 512 kb)

MT4LC16M4A7 16M * 8 (128 Mbps, 16 Mb)

MT4LC2M8E7 2M * 8 (16 Mbps, 2 Mb, EDO)

MT4C16270 256k * 16 (4 Mbps, 512 kb, EDO)

EDO circuits often (but not always) have “not round” numbers in their designations: for example, 53C400 - ordinary DRAM, 53C408 - EDO DRAM.

In addition, memory microcircuits can vary in cases and types of modules. There are DIP, SIP, SIPP, SIMM, DIMM, CELP, COAST.

DIP (Dual In line Package - a case with two series of outputs) - classic microcircuits used in the main memory blocks XT and earlier AT, and now - in the cache blocks.

SIP (Single In line Package - case with one row of conclusions) - a microcircuit with one row of conclusions, installed vertically. SIPP (Single In line Pinned Package - module with one row of wire outputs) - a memory module inserted into a panel like DIP / SIP microcircuits; used in earlier AT.

SIMM (Single In line Memory Module - a memory module with one row of contacts) - a memory module inserted into the clamping connector; It is used in all modern motherboards, as well as in many adapters, printers and other devices. SIMM has contacts on two sides of the module, but they are all interconnected, forming as if one row of contacts.

DIMM (Dual In line Memory Module - a memory module with two rows of contacts) is a memory module similar to SIMM, but with separate contacts (usually 2 x 84), which increases the bit size or the number of memory banks in the module. It is mainly used in Apple computers and the new P5 and P6 boards.

On SIMM, FPM / EDO / BEDO microcircuits are currently predominantly installed, and EDO / BEDO / SDRAM on DIMMs.

CELP (Card Egde Low Profile - a low card with a knife edge connector) is an external cache module assembled on SRAM (asynchronous) or PB SRAM (synchronous) microcircuits. By appearance  similar to 72-pin SIMM, has a capacity of 256 or 512 kb. Another name is COAST (Cache On A STick - literally "cache on a stick").

Dynamic memory modules, in addition to data memory, can have additional memory for storing parity bits (Parity) for data bytes - such SIMMs are sometimes called 9- and 36-bit modules (one parity bit per data byte). Parity bits are used to control the correct reading of data from the module, allowing to detect some errors (but not all errors). It makes sense to use modules with parity only where very high reliability is needed - thoroughly tested modules without parity are also suitable for ordinary applications, provided that the system board supports these types of modules.

The easiest way to determine the type of module is by marking and the number of memory chips on it: for example, if on a 30-pin SIMM there are two chips of the same type and one is different, then the first two contain data (each of them contains four bits), and the third contains parity bits it is single-bit). In a 72-pin SIMM with twelve microcircuits, eight of them store data, and four - parity bits. Modules with 2, 4 or 8 chips do not have parity memory.

Sometimes the so-called parity simulator is placed on the modules - an adder chip, which always gives the correct parity bit when reading a cell. It is mainly intended for installing such modules in boards where the parity check is not disabled; however, there are modules where such an adder is labeled as an "honest" memory chip - most often such modules are manufactured in China. Most SIMMs are made by Acorp, Hunday.

Comparison of memory devices.  We briefly examined almost all existing memory devices that are currently used in computers as operational and long-term memory.

For a long time, there was a noticeable gap between the main and permanent memory devices in such basic parameters as memory access time and memory capacity (in access time from 5 · 10 -3 to 10 -3 s, i.e. almost three orders of magnitude) . So, traditional rAM  on shift registers significantly differed in access time from memory on magnetic disks or drums.

Even more notable successes have occurred in solving the problem of increasing memory capacity. Of particular note is the memory on optical disks, where the capacity can be measured up to 6 · 10 3 Mbit, and the maximum access time to the memory is 10 -5 s. Note, by the way, that 104 Mbit is about 3 thousand medium-sized books of 200 pages each.

Apparently, the time is not far off when it will be possible to create one type of memory in a computer without dividing it into operational and permanent.

Floppy disk ( floppy disk or floppy disk) - can store information for a long time. Diskette capacity 3.5 ’’ (disk diameter) - 1 MB. They are disk-shaped and fit in a plastic case. Read from a floppy disk and write information to a floppy disk using drive.

[Laser disk  contains a lot of information (CD-ROM - 700 MB or more DVD-ROM - from 4.7 GB to 17 GB). Laser disks have the shape of a disk made of a special material that perceives laser burning. Information from laser discs  read by special drives ( CD-ROM, CD-RW-drives, DVD-ROM, DVD-RW-drives). RW drives are designed not only for reading, but also for burning CDs.

[ Flash memory  - intermittent storage device consisting of an electronic microcircuit. It is used to store mutable information. Flash replaces dozens of floppy disks, compact and reliable. Flash memory is implemented in small devices (Flash key fobs). USB ports are used to work with flash drives.

: HDD (winchester) can store information for a long time. They are several dozen disks enclosed in a metal case. The largest information stored on the hard drive is determined by its type and ranges from 1 megabyte to several gigabytes. The hard drive is located in the system unit.

[ Replaceable cartridges  with magnetic tape with capacities from 20 MB to 2 GB. For work with cartridges streamers are used.

1 random access memory ( RAM) or OP stores information only during computer operation, during its processing. OP capacity is from 1 Kb to 512 Kb.

1 Buffer (clipboard)  briefly stores limited information that must be moved or copied from one part of the information medium to another or from one file to another.

To store information on a disk, the disk must be formatted . The magnetic head of the drive marks the tracks and sectors. Formatting – creation of the logical and physical structure of the disk, i.e. marking the disc on tracks (tracks) using concentric circles and sectors using radii.

Formatting a flash drive is not necessary, but sometimes there is a need to format the flash drive! For example, if you are a user of an operating system below Windows 2000 *. As a rule, flash drives of large volumes are formatted in NTFS format, which may be a problem for determining the old USB drive operating systems. To fix this problem, you can try to format the flash drive in FAT32 format.

Parameters floppy disk  3.5 "format:

· Sector information volume - 512 bytes

· The number of sectors on the track - 18

· Tracks on one side - 80

· Parties - 2.

Number of sectors: N \u003d 18 * 80 * 2 \u003d 2,880

Information disk capacity: 512 bytes * N \u003d 1,474,560 bytes \u003d 1,440 KB \u003d 1.40625 MB