Personal computer: external memory. How to keep an archive for decades

External memory is a memory implemented as external, relatively motherboard, devices with different principles of information storage and types of media designed for long-term storage information. In particular, all computer software is stored in external memory. External memory devices can be placed both in the computer system unit and in separate cases. Physically, external memory implemented in the form of drives. Drives - These are storage devices designed for long-term (which does not depend on power supply) storage of large amounts of information. Drive capacity is hundreds of times greater than capacity random access memory or even unlimited when it comes to removable media drives.

A drive can be considered as a combination of carrier and corresponding drive. There are drives with removable and permanent media. A drive is a combination of a read-write mechanism with corresponding electronic control circuits. Its design is determined by the principle of action and the type of carrier. A medium is a physical medium for storing information. appearance can be disk or tape. According to the principle of memorization, magnetic, optical and magneto-optical carriers are distinguished. Tape media can only be magnetic; in disk media, they use magnetic, magneto-optical and optical methods of recording and reading information.

The most common are drives on magnetic diskswhich are divided into drives on hard magnetic drives (HDD) and floppy drives (HMD), and optical disc drivessuch as CD-ROM, CD-R, CD-RW and DVD-ROM drives.

Hard Disk Drives (HDD)

HDD is the main device for long-term storage of large volumes of data and programs. Other names: hDD, Winchester, HDD (Hard Disk Drive). Externally, the hard drive is a flat, hermetically sealed box, inside of which are located on a common axis several rigid aluminum or glass plates of a circular shape. The surface of any of the disks is covered with a thin ferromagnetic layer (a substance that reacts to an external magnetic field), the recorded data is actually stored on it. In this case, recording is carried out on both surfaces of each plate (except the extreme ones) using a block of special magnetic heads. Each head is located above the working surface of the disk at a distance of 0.5-0.13 microns. The package of disks rotates continuously and with a high frequency (4500-10000 rpm), therefore mechanical contact of heads and disks is unacceptable.

Writing data to the hard disk is as follows. When changing the strength of the current passing through the head, there is a change in the intensity of the dynamic magnetic field in the gap between the surface and the head, which leads to a change in the stationary magnetic field of the ferromagnetic parts of the disk coating. The read operation occurs in the reverse order. Magnetized particles of a ferromagnetic coating are the cause of the electromotive force of the self-induction of the magnetic head. The electromagnetic signals that arise in this case are amplified and transmitted for processing.
The work of the hard drive is controlled by a special hardware-logical device - the controller hard drive. In the past, it was a separate daughterboard that was connected via slots to the motherboard. In modern computers, the functions of the hard disk controller are performed by special microcircuits located in the chipset.

A drive can have up to ten disks. Their surface is divided into circles, which are called tracks (track). Each track has its own number. Tracks with the same numbers, located one above the other on different disks form a cylinder. The tracks on the disk are divided into sectors (numbering starts from one). The sector occupies 571 bytes: 512 is reserved for recording the necessary information, the rest under the heading (prefix) that defines the beginning and number of the section and the end (suffix), where the checksum is recorded to verify the integrity of the stored data. Sectors and tracks are formed during disk formatting. Formatting is performed by the user using special programs. No information can be written to an unformatted disk. The hard drive can be divided into logical drives. This is convenient because having multiple logical drives simplifies the structuring of data stored on your hard drive.

There are a huge number of different models hard drives many firms such as Seagate, Maxtor, Quantum, Fujitsu, etc. To ensure the compatibility of hard drives, standards have been developed for their characteristics that determine the nomenclature of the connecting conductors, their placement in the adapter connectors, and the electrical parameters of the signals. Common are the IDE (Integrated Drive Electronics) or ATA interface standards and the more productive EIDE (Enhanced IDE) and SCSI (Small Computer System Interface). Characteristics of the interfaces through which hard drives are associated with motherboard, largely determine the performance of modern hard drives.

Among other parameters that affect the performance of the HDD, the following should be noted:

disk speed - Nowadays, EIDE drives with a rotation frequency of 4500-7200 rpm are produced, and SCSI drives - 7500-10000 rpm;
cache capacity - in all modern disk drives a cache buffer is installed that speeds up data exchange; the larger its capacity, the higher the likelihood that the cache will contain the necessary information that does not need to be read from the disk (this process is thousands of times slower); cache buffer capacity in different devices can vary in the range from 64 KB to 2 MB;
average access time - time (in milliseconds) during which the block of heads is shifted from one cylinder to another. Depends on the design of the actuator and is approximately 10-13 milliseconds;
delay time - this is the time from the moment the head block is positioned on the desired cylinder to the position of a particular head on a particular sector, in other words, this is the time to search for the desired sector;
exchange rate - determines the amount of data that can be transferred from the drive to the microprocessor and in the opposite direction for certain periods of time; the maximum value of this parameter is equal to the bandwidth disk interface and depends on which mode is used: PIO or DMA; in PIO mode, data exchange between the disk and the controller occurs with the direct participation of the central processor, the higher the PIO mode number, the higher the exchange rate; work in DMA (Direct Memory Access) mode allows you to transfer data directly to RAM without the participation of the processor; data transfer rate in modern hard drives fluctuates in the range of 30-60 MB / s.

Floppy Disk Drives (HMD)

A hard disk drive or drive is mounted in the system unit. Flexible media for hard disk drives are produced in the form of floppy disks (another name is floppy disk). Actually, the carrier is a flat disk with a special, fairly dense film coated with a ferromagnetic layer and placed in a protective envelope with a movable gate in the upper part. Floppy disks are used mainly for the rapid transfer of small amounts of information from one computer to another. Data recorded on a floppy disk can be protected from erasure or overwriting. To do this, you need to move the small protective shutter in the lower part of the diskette so that an open window is formed. In order to allow recording, this valve should be moved back and close the window.

The front panel of the drive is displayed on the front panel of the system unit, on it there is a pocket closed by a curtain, where a diskette is inserted, a button for removing the diskette and an indicator lamp. The diskette is inserted into the drive with the upper bolt forward, it must be inserted into the drive pocket and gently push forward until it clicks. The correct direction to insert the floppy disk is indicated by an arrow on the plastic case. To remove a diskette from the drive, you need to click on its button. The indicator light on the drive indicates that the device is busy (if the light is on, it is not recommended to remove the diskette). Unlike a hard drive, a drive in a hard drive is rotated only with a read or write command; at other times, it is at rest. The read-write head during operation mechanically contacts the surface of the floppy disk, which leads to rapid wear of the floppy disks.

As with a hard drive, the surface floppy disk splits into tracks, which in turn are split into sectors. Sectors and tracks are obtained during disk formatting. Now floppy disks are delivered formatted.

The main parameters of a floppy disk are the technological size (in inches), recording density and full capacity. The sizes distinguish between 3.5-inch floppy disks and 5.25-inch diskettes (now no longer used). The recording density can be simple SD (Single Density), Double DD (Double Density) and High HD (High Density). The standard capacity of the 3.5-inch floppy disk is 1.44 MB, it is possible to use floppy disks with a capacity of 720 KB. Currently, 3.5-inch, high-density HD floppy disks with a capacity of 1.44 MB are standard.

When using a diskette, you should adhere to the following rules:

do not touch the working surface of the diskette;
do not bend the diskette;
do not remove the metal valve; a dirty diskette may damage the heads;
keep floppy disks away from the source of magnetic fields;
before use, check the floppy disk for viruses using an antivirus program.

Optical disc drives

CD-ROM drive

Since 1995, instead of 5.25 inches, the CD-ROM drive has been included in the basic configuration of a personal computer instead of 5.25-inch drives. The abbreviation CD-ROM (Compact Disk Read Only Memory) translates as read-only media based on CDs. The principle of operation of this device is to read digital data using a laser beam that is reflected from the surface of the disk. As an information carrier, a regular CD-ROM is used. Digital recording on a CD differs from recording on magnetic disks in high density, so a standard CD has a capacity of about 650-700 MB. Such large volumes are characteristic of multimedia information (graphics, music, video), therefore, CD-ROM drives are multimedia hardware. In addition to multimedia publications (electronic books, encyclopedias, music albums, videos, computer games), a variety of system and application software of large volumes (operating systems, office suites, programming systems, etc.) is distributed on CD-ROMs.

Compact discs are made of transparent plastic with a diameter of 120 mm. and 1.2 mm thick. A layer of aluminum or gold is sprayed onto the plastic surface. In conditions of mass production, information is written to a disc by extruding on the surface of a track in the form of a series of recesses. This approach provides binary information recording. Deepening (pit - pit), surface (land - land). Logical zero can be represented by both pit and land. The logical unit is encoded by the transition between the pet and the land. From the center to the edge of the CD, there is a single track in the form of a spiral 4 microns wide with a pitch of 1.4 microns. The surface of the disk is divided into three areas. Initial (Lead-In) is located in the center of the disk and is read first. It contains the contents of the disc, a table of addresses of all the records, the label of the disk and other overhead information. The middle area contains basic information and occupies most of the disk. End Area (Lead-Out) contains the label of the end of the disk.

For stamping, there is a special prototype matrix (master disk) of the future disc, which extrudes tracks on the surface. After stamping, a protective film of transparent varnish is applied to the surface of the disc.

The CD-ROM drive contains:

an electric motor that rotates the disk;
an optical system consisting of a laser emitter, optical lenses and sensors and designed to read information from the surface of the disk;
a microprocessor that controls the mechanics of the drive, the optical system, and decodes the read information into binary code.

The compact disk is untwisted by the electric motor. A beam from a laser emitter is focused on the surface of a disk using an optical drive. The beam is reflected from the surface of the disk and fed through the prism to the sensor. The luminous flux is converted into an electrical signal, which enters the microprocessor, where it is analyzed and converted into a binary code.

Key features of the CD-ROM:

data transfer rate - measured in multiples of the speed of an audio CD player (150 Kb / s) and characterizes the maximum speed with which the drive sends data to the computer’s RAM, for example, a 2-speed CD-ROM (2x CD-ROM) will read data at a speed of 300 KB / sec., 50-speed (50x) - 7500 KB / sec .;
access time - the time required to search for information on the disk, measured in milliseconds.

The main disadvantage of standard CD-ROMs is the inability to record data, but there are CD-R and CD-RW rewritable devices.

CD-R drive (CD-Recordable)

Outwardly similar to CD-ROM drives and compatible with them in disk size and recording format. Allow one-time recording and unlimited readings. Data is recorded using a special software. The write speed of modern CD-R drives is 4x-8x.

CD-RW drive (CD-ReWritable)

Used for rewriting data, and you can simply add new information to free space, and completely overwrite the disk with new information (previous data is destroyed). As in the case of CD-R drives, for recording data you must install in the system special programsand the recording format is compatible with a conventional CD-ROM. The write speed of modern CD-RW drives is 2x4-4.

DVD drive (Digital Video Disk)

A device for reading digital videos. Externally, the DVD-ROM is similar to a regular CD-ROM (diameter - 120 mm, thickness 1.2 mm), but differs from it in that up to 4.7 GB can be recorded on one side of the DVD, and up to two on two 9.4 GB In the case of using a two-layer recording scheme, up to 8.5 GB of information can already be placed on one side, respectively, about 17 GB on two sides. DVD discs can overwrite information.

The most important factor restraining the widespread use of CD-R, CD-RW and DVD drives is the high cost of both themselves and removable media.

test questions

What is external memory? What kinds of external memory do you know?
What is a hard drive? What is it for? What capacity do modern hard drives have?
How are read and write operations performed in HDD?
What is the operation of formatting magnetic disks?
What are the types of standard disk interfaces?
What parameters affect the performance of the hard drive? How?
What is a floppy disk? What is common and different between him and hard drive?
What rules should be followed when using a floppy disk?
What kinds of optical disc drives do you know? How do they differ among themselves?
How is information read from CDs?
What is the data transfer rate measured in optical storage devices?

Computer science. Basic course. / Ed. S.V.Simonovich. - SPb., 2000
A.P. Miklyaev, Handbook of the user of IBM PC 3-edition M.:, "Solon-R", 2000, 720 p.
Simonovich S.V., Evseev G.A., Murakhovsky V.I. You bought a computer: Complete guide for beginners in questions and answers. - M .: AST-PRESS BOOK; Inforkom-Press, 2001.- 544 pp., Ill. (1000 tips).
Kovtanyuk Yu.S., Solovyan S.V. The self-instruction manual on the personal computer - K.: Junior, 2001.- 560s., Ill.

ALL-RUSSIAN CURRENT FINANCIAL AND ECONOMIC

INSTITUTE

DEPARTMENT OF AUTOMATED PROCESSING

ECONOMIC INFORMATION

COURSE WORK

discipline: "Computer science"

on the topic "Long-term storage of data on a PC"

Executor:

specialty marketing

daytime group

Head:

Introduction

In the theoretical part of this course work will be considered devices for long-term storage of information.

Long-term storage devices on a PC belong to the external memory of the device, allowing you to save information for later use regardless of the state of the computer (on or off). Data storage devices can use various physical principles of information storage - magnetic, optical, electronic - in any of their combinations. External memory is fundamentally different from internal (operational, permanent and special) memory in the way the processor (executable program) accesses its contents.

A characteristic feature of external memory is that its devices operate with blocks of information, but not bytes or words, as RAM allows. These blocks usually have a fixed size multiple of the power of 2. A block can be rewritten from internal memory to the external or vice versa only in its entirety, and a special procedure (subroutine) is required to perform any exchange operation with external memory. The exchange procedures with external memory devices are tied to the type of device, its controller and how the device is connected to the system (interface).

The object of study is data storage devices, the subject is long-term data storage devices on a PC.

In the practical part, the problem will be solved:

To solve this problem, it is most advisable to use the MS Excel application package. Its use can be justified by the following:

This package has all the means of calculation necessary to complete the task;

There is a developed subsystem for constructing graphs and charts;

This package of applications is by far the most common on personal computers, which allows you to use the forms created for calculating in the future for similar tasks in the real work of an economist.

The task was solved in the version of MS Excel 2003.

I . Theoretical part

1. The basic concepts used in the study of devices for long-term storage of information

External memory is a memory implemented in the form of external, relative to the motherboard, devices with different principles of information storage and types of media designed for long-term storage of information. In particular, all computer software is stored in external memory. External memory devices can be placed both in the computer system unit and in separate cases. Physically, external memory is implemented as drives. Storage devices are storage devices designed for long-term (which does not depend on power supply) storage of large amounts of information. The storage capacity is hundreds of times higher than the RAM capacity or even unlimited when it comes to removable storage drives.

A drive can be considered as a combination of carrier and corresponding drive. There are drives with removable and permanent media. A drive is a combination of a read-write mechanism with corresponding electronic control circuits. Its design is determined by the principle of action and the type of carrier. A medium is a physical medium for storing information; in appearance, it can be disk or tape. According to the principle of memorization, magnetic, optical and magneto-optical carriers are distinguished. Tape media can only be magnetic; in disk media, they use magnetic, magneto-optical and optical methods of recording and reading information.

2. Classification of devices for long-term storage of information

The most common are magnetic disk drives, which are divided into hard disk drives (HDD) and floppy disk drives (HDD), and optical disk drives such as CD-ROM, CD-R, CD-RW and DVD-ROM

3. Detailed characteristics of devices for long-term storage of information

· Hard Disk Drives (HDD))

HDD is the main device for long-term storage of large volumes of data and programs. Other names: hard disk, hard drive, HDD (Hard Disk Drive). Externally, the Winchester is a flat, hermetically sealed box, inside of which are located on a common axis several rigid aluminum or glass plates of a circular shape. The surface of any of the disks is covered with a thin ferromagnetic layer (a substance that reacts to an external magnetic field), the recorded data is actually stored on it. In this case, recording is carried out on both surfaces of each plate (except the extreme ones) using a block of special magnetic heads. Each head is located above the working surface of the disk at a distance of 0.5-0.13 microns. The package of disks rotates continuously and with a high frequency (4500-10000 rpm), therefore mechanical contact of heads and disks is unacceptable.

There are a huge number of different models of hard drives of many companies, such as Seagate, Maxtor, Quantum, etc. To ensure the compatibility of hard drives, standards have been developed for their characteristics that determine the nomenclature of the connecting conductors, their placement in the adapter connectors, and the electrical parameters of the signals. Common are the IDE (Integrated Drive Electronics) or ATA interface standards and the more productive EIDE (Enhanced IDE) and SCSI (Small Computer System Interface). The characteristics of the interfaces through which the hard drives are connected to the motherboard, to a large extent determine the performance of modern hard drives.

- disk speed - Nowadays, EIDE drives with a rotation frequency of 4500-7200 rpm are produced, and SCSI drives - 7500-10000 rpm;

- cache capacity - In all modern disk drives, a cache buffer is installed that speeds up data exchange; the greater its capacity, the higher the likelihood that the cache will necessary information, which does not need to be read from disk (this process is thousands of times slower); the cache buffer capacity in different devices can vary from 64 KB to 2 MB;

- average access time - time (in milliseconds) during which the block of heads is shifted from one cylinder to another. Depends on the design of the actuator and is approximately 10-13 milliseconds;

- delay time - this is the time from the moment the head block is positioned on the desired cylinder to the position of the specific head on a particular sector, in other words, this is the search time for the desired sector;

- exchange rate - determines the amount of data that can be transferred from the drive to the microprocessor and in the opposite direction for certain periods of time; the maximum value of this parameter is equal to the bandwidth of the disk interface and depends on which mode is used: PIO or DMA; in PIO mode, data exchange between the disk and the controller occurs with the direct participation of the central processor, the higher the PIO mode number, the higher the exchange rate; work in DMA (Direct Memory Access) mode allows you to transfer data directly to RAM without the participation of the processor; The data transfer speed in modern hard drives ranges from 30-60 MB / s.

· Floppy Disk Drives (HMD)

Since 1995, in the basic configuration of a personal computer, instead of 5.25-inch drives, they began to include a CD-ROM drive. The abbreviation CD-ROM (Compact Disk Read Only Memory) translates as read-only media based on CDs. The principle of operation of this device is to read digital data using a laser beam that is reflected from the surface of the disk. As an information medium, a regular CD-ROM is used. Digital recording on a CD differs from recording on magnetic disks in high density, so a standard CD has a capacity of about 650-700 MB. Such large volumes are characteristic of multimedia information (graphics, music, video), therefore, CD-ROM drives are multimedia hardware. In addition to multimedia publications (e-books, encyclopedias, music albums, videos, computer games), a wide variety of system and application software is distributed on CDs ( operating Systems, office suites, programming systems, etc.).

Compact discs are made of transparent plastic with a diameter of 120 mm and a thickness of 1.2 mm. A layer of aluminum or gold is sprayed onto the plastic surface. In conditions of mass production, information is written to a disc by extruding on the surface of a track in the form of a series of recesses. This approach provides binary information recording. Deepening (pit - pit), surface (land - land). Logical zero can be represented by both pit and land. The logical unit is encoded by the transition between the pet and the land. From the center to the edge of the CD, there is a single track in the form of a spiral 4 microns wide with a pitch of 1.4 microns. The surface of the disk is divided into three areas. Initial (Lead-In) is located in the center of the disk and is read first. It contains the contents of the disc, a table of addresses of all the records, the label of the disk and other overhead information. The middle area contains basic information and occupies most of the disk. End Area (Lead-Out) contains the label of the end of the disk.

- data rate - measured in multiples of the speed of an audio CD player (150 Kb / s) and characterizes the maximum speed with which the drive sends data to the computer’s RAM, for example, a 2-speed CD-ROM (2x CD-ROM) will read data at a speed 300 Kb / s; 50-speed (50x) - 7500 Kb / s;

- access time - the time required to search for information on the disk is measured in milliseconds.

The main disadvantage of standard CD-ROMs is the inability to record data, but there are CD-R and CD-RW rewritable devices.

Outwardly similar to CD-ROM drives and compatible with them in disk size and recording format. Allow one-time recording and unlimited readings. Data recording is carried out using special software. The write speed of modern CD-R drives is 4x-8x.

They are used for rewriting data, and you can either simply add new information to free space or completely overwrite the disk with new information (previous data is deleted). As in the case of CD-R drives, it is necessary to install special programs in the system to record data, and the recording format is compatible with a regular CD-ROM. The write speed of modern CD-RW drives is 2x4-4.

1. General characteristics of the task

The task: The organization Triumph OJSC provides certain types of loans to both individuals and legal entities at interest rates (Fig. 1). The company keeps a register of loans and their repayments (Fig. 2). At the same time, for each overdue return day, a penalty of 1% of the loan amount is charged.

The task:

1. To build tables on the given data

Fig. 1. The list of types of loans and their interest rates in Triumph OJSC

2. Organize inter-table communications for automatically filling in the column of the loan registration journal (Fig. 2): “Name of loan”, “Amount of repayment under the agreement, thousand rubles.”, “Penalties, thousand rubles.”, “Total amount of repayment, thousand roubles.".

date of issue	Borrower (company name or full name)	Loan Type Code	Loan name	Loan amount, thousand rubles	Contract return period	Real date of loan repayment	Contract Refund Amount	Penalties, thousand rubles	Total amount of return, thousand rubles
	Ivanov I.I.
	Sidorov S.S.
	IP Terekh O.A.
	Selyanov G.E.
	CJSC Dnepr
	Petrov R.M.
	Vavilova V.P.
	IP Bekas P.N.

Fig. 2. Creditors Registration Journal

3. Determine the most popular type of loan:

1) to summarize in the loan registration journal;

2) Build the appropriate pivot table.

4. To build a histogram according to the data of the pivot table

2. Description of the algorithm for solving the problem

1. Run the MS Excel spreadsheet processor.

2. Create a book with the name "12th option."

3. Rename sheet 1 to a sheet called List.

4. On the “List” sheet of MS Excel, create a table of a list of types of loans and their interest rates at Triumph OJSC.

5. Fill in the table of the list of types of loans and rates for them with data (Fig. 1)

fig. 1. Location of the table “List of types of credit and interest rates at Triumph OJSC

6. Rename sheet 2 to a sheet with the name "Registration of loans."

7. On the MS Excel Loans Registration worksheet, create a loan log table.

8. Fill in the table “Credit registration journal” with initial data (Fig. 2)

fig. 2. Location of the table “Credit registration journal”

9. Fill in the column “Name of loan” of the table “Journal of registration of loans” located on the sheet “registration” as follows:

Put in the cell D3 the formula:

\u003d IF (C3 \u003d 100; List! $ B $ 3; IF (C3 \u003d 200; List! $ B $ 4; IF (C3 \u003d 300; List! $ B $ 5; IF (C3 \u003d 400; List! $ B $ 6; IF (C3 \u003d 500; List! $ B $ 7)))))

Multiply the formula entered in cell D3 for the remaining cells (D4 to D10) of this column.

10. Fill in the column “Amount of repayment under the agreement, thousand rubles” of the table “Journal of registration of loans”, located on the sheet “Registration of loans” as follows:

Enter in the cell H3 the formula:

\u003d IF (C3 \u003d 100; E3 * List! $ C $ 3; IF (C3 \u003d 200; E3 * List! $ C $ 4; IF (C3 \u003d 300; E3 * List! $ C $ 5; IF (C3 \u003d 400; E3 * List! $ C $ 6; IF (C3 \u003d 500; E3 * List! $ C $ 7))))) + E3

Multiply the formula entered in cell H3 for the remaining cells (from H4 to H10) of this column.

11. Fill in the column “Penalties, thousand rubles” of the table “Journal of registration of loans”, located on the sheet “Registration of loans” as follows:

Enter in formula I3 the formula:

Multiply the formula entered in cell I3 for the remaining cells (I4 to I10) of this column.

12. Fill in the column "Total repayment amount, thousand rubles" of the table "Journal of registration of loans", located on the sheet "Registration of loans" as follows:

Put in the cell J3 the formula:

Multiply the formula entered in cell J3 for the remaining cells (J4 to J10) of this graph.

13. In the table “Loans registration journal”, summarize the total in the journal for the field “Loan amount, thousand rubles”, “Amount of return under the agreement, thousand rubles”, “Penalties, thousand rubles.”, “Total amount of repayment , thousand rubles ”(Fig. 3)

fig. 3. Registration of loans issued by Triumph OJSC to physical

and legal entities

14. Rename sheet 3 to a sheet called a Pivot Table.

15. On the worksheet "Pivot table » MS Excel create a table in which there will be payment amounts for certain types of loans.

16. Create a pivot table to identify the most popular loan. To do this, use the wizard to build pivot tables (Fig. 4)

fig. 4. Summary table of Triumph OJSC

17. Rename sheet 4 to a sheet called "Chart."

18. On the worksheet “Diagram” MS Excel present graphically the results of the calculations of the summary table of JSC “Triumph” (Fig. 5)

fig. 5. Graphical representation of calculation results

List of references:

1. Simonovich S., Evseev G. General informatics. Tutorial. M.,

2. Semakin I.G. Computer science. Tutorial. M., 2001.S. 66.

3. Roganov EA Fundamentals of computer science. Tutorial. M., 2007.S. 177.

4. Mogilev A.V. Information Technology. Tutorial. M., 2003.

5. Makarova N.V. Computer science. Tutorial. M., 2003.S. 189.

6. Vilkhovichenko S. Modern computer. SPb., Textbook. M.,

7. Veretennikova E.G., Patrushina S.M., Savelyeva N.G. Computer science:

Textbook for universities. M., 2003.S. 155.

8. Kiyashko A.B. Computer science. Tutorial. M., 2006. P.145.

9. Makarova N.V. Computer science. Tutorial. M., 2003. S. 45.

10. Makarova N.V. Computer science. Tutorial. M., 2006. P.34

11. Makarova N.V. Computer science. Tutorial. M., 2003.S. 56.

Introduction

Modern society is characterized by the intensive development of hardware and software. Based on the timely replenishment, accumulation, processing of an information resource, rational management and adoption of correct decisions are possible. This is especially important for the economy. The constant growth of information flows places high demands on the use of data storage devices. In this regard, the consideration of the issue of means of long-term storage of information seems to be very relevant.

In this paper, attention is paid to a separate element of the architecture of a personal computer, known as “external memory”. The presentation of the material begins with the formation of a general idea of \u200b\u200bthe subject of study. This is followed by coverage of the most important components of the selected topic. Each section sequentially reveals the features of these devices, in particular, the essence of the tool, its functions, technical characteristics, scope and conditions of use.

The practical part of the presented work is devoted to solving the economic problem. According to the above data, the total amount of repayment under the loan agreement was calculated. Similar calculations can be applied in a number of economic and financial-credit organizations. The calculations are accompanied by comments on the task execution algorithm, the construction of the corresponding tables and graphic element.

The work was carried out on an IBM PC with a standard configuration, including a system unit, a monitor, a keyboard, a mouse with the following characteristics: 64-bit 2.4 GHz Celeron microprocessor, 1024 MB RAM, Samsung 80 GB hard drive, Samsung 3.5-inch drive, CD-RW LG 52x32x52, Acer 17 "monitor with a resolution of 1280x1024. The work was carried out in Windows XP using a text editor Microsoft Office Word 2003, a table processor Microsoft Office Excel 2003, included in the integrated Microsoft Office 2003 RFP.

1. Long-term storage devices on a PC

Introduction 4

1.1. Classification of PC External Memory Devices 5

1.2. Descriptions of specific species 6

Floppy disk 6

Cd 7

Hard drive 12

Flash memory 18

Conclusion 20

Introduction

A personal computer is designed to automate the processing of information. In this case, the data are entered into the computer using input devices and are subject to further processing. However, quite often there is a need to store and transfer large amounts of information. Permanent storage of such information arrays in the computer's memory seems irrational. When these factors are taken into account, devices for long-term data storage, which is also called external memory, are widely used.

External (long-term) memory (VZU - external storage device) is designed for long-term storage of programs and data not currently used in the PC’s RAM, and is non-volatile, i.e. the integrity of its contents does not depend on whether the computer is turned on or off. In particular, all PC software is stored in external memory. Unlike RAM, external memory does not have a direct connection with the processor. External storage media, in addition, provide data transport in cases where computers are not connected to a network (local or global).

Classification of external PC memory devices

External memory devices or, otherwise, external storage devices are very diverse. They can be classified according to a number of signs: by type of carrier, type of construction, by the principle of recording and reading information, access method, etc.

One of the possible classification options for VZU is presented below in Fig. 2.

Fig. 2. Classification of VZU

To work with external memory, you must have a drive (a device that provides recording and (or) reading information) and a storage device - media.

Depending on the type of media, all VZU can be divided into magnetic tape drives and disk drives.

Magnetic tape drives, in turn, are of two types: bobbin magnetic tape drives (NBML) and cassette tape drives (NKML - tape drives). Only streamers are used on a PC.

Disk drives are devices for writing / reading from magnetic (optical) media. The purpose of these drives: storage of large volumes of information, recording and issuing stored information on request to a random access memory. Drives refer to direct access machine storage media. The concept of direct access means that the PC can “go” to the track where the section with the desired information begins or where you want to write new information directly, wherever the drive’s write / read head is located.

Thus, the main devices for long-term data storage include:

floppy disk drives (HMD);

hard disk drives (HDD);

optical disc drives (CD, CD-RW);

storage media for recording magneto-optical disks;

tape drives (tape drives), etc.

1.2 Description of specific species:

D isketa

A floppy disk is a portable magnetic storage medium used for multiple recording and storage of relatively small data. This type of carrier was especially common in the 1970s and early 2000s. Instead of the term “floppy disk” the abbreviation HMD is sometimes used - “flexible magnetic disk” (accordingly, a device for working with floppy disks is called HMD - “floppy disk drive”, the slang version is a floppy drive, floppy, floppy from English floppy-disk).

Typically, a floppy disk is a flexible plastic plate covered with a ferrimagnetic layer, hence the English name “floppy disk” (“floppy disk”). This plate is placed in a plastic case that protects the magnetic layer from physical damage. The shell is flexible or durable. Writing and reading floppy disks is carried out using a special device - a drive (floppy drive).

Floppy disks usually have a write-protect function, through which you can provide access to data only in read mode.

Currently, floppy disks are almost everywhere replaced by more capacious and much lower unit costs types of drives. These include, first of all, flash drives, recordable CDs and DVDs (especially DVD-RAM).

Compact disc

(“CD”, “Shape CD”, “CD-ROM”, “CD ROM”) is an optical information carrier in the form of a disk with a hole in the center, the information from which is read out using a laser. Initially, the CD was created for digital storage of audio (the so-called Audio-CD), however, it is now widely used as a general-purpose storage device (the so-called CD-ROM). The abbreviation "CD-ROM" means "Compact Disc Read Only Memory" which means a readable compact disc. "CD ROM" means "CD-ROM, read only memory." CD-ROM’s is often mistakenly called a CD-ROM drive. The CD was created in 1979 by Philips and Sony.

Compact discs are made of polycarbonate with a thickness of 1.2 mm, coated with the thinnest layer of aluminum (previously used gold) with a protective layer of varnish, on which a graphical representation of the disc content is usually applied. Therefore, contrary to popular belief, the CD-ROM should never be put upside down (label down), since the reflective aluminum layer on which the data is stored is protected from below, as was said above, with a 1.2 mm layer of polycarbonate, and on top - only a thin layer of varnish. In addition, on the reflective side there is an annular protrusion 0.5 mm high, which allows the disk, laid on a flat surface, not to touch this surface. A hole with a diameter of 15 mm is located in the center of the disk (if desired, the disk can be carried by putting it on a finger without touching its surface at all).

Information on the disc is recorded in the form of a spiral track of the so-called pits (indentations) extruded on the aluminum layer (in contrast to the CD-ROM recording technology where information is recorded cylindrically). Each pit has approximately 125 nm in depth and 500 nm in width. The length of the pit varies from 850 nm to 3.5 microns. The distance between adjacent spiral paths is 1.5 microns. Data from the disk is read using a laser beam with a wavelength of 780 nm, which is visible through the polycarbonate layer, reflected from the aluminum and read by the photodiode. The laser beam forms a spot with a diameter of about 1.5 microns on the reflective layer. Since the disc is read from the bottom, each pit looks like an elevation to the laser. Places where there are no such elevations are called platforms.

To make it easier for you to imagine the ratio of disk and pit sizes: if the CD were the size of a stadium, the pit would be about the size of a grain of sand.

The light from the laser entering the site is reflected and captured by the photodetector. If the light hits the elevation, it experiences interference with the light reflected from the area around the elevation and does not reflect. This is because the height of each elevation is equal to a quarter of the wavelength of the laser light, which leads to a phase difference of half the wavelength between the light reflected from the site and the light reflected from the elevation.

Compact discs are stamped at the factory (CD-ROM), CD-R for write once, CD-RW for multiple recording. The discs of the last two types are intended for recording at home on special writing drives. In some CD players and music centers, such discs may not be readable (recently all manufacturers of household music centers and CD players include CD-R / RW reading support in their devices).

The CD read / write speed is a multiple of 150 KB / s (i.e. 153,600 bytes / s). For example, a 48-speed drive provides the maximum read (or write) speed of CDs equal to 48 * 150 \u003d 7200 KB / s (7.03 MB / s).

The weight of the disk without a box is ~ 15.7 g. The weight of the disk in a regular (not "slim") box is ~ 74 g.

Shape CD (figured compact disk) - an optical medium of digital information such as CD-ROM, but not strictly round, but with the outline of an external contour in the form of various objects, such as portraits, cars, planes, Disney characters, hearts, stars, ovals , in the form of credit cards, etc.

There are also discs for home recording: CD-R (Compact Disc Recordable) for single recording and CD-RW (Compact Disc ReWritable) for multiple recording. In such discs, the reflectivity of the pits and the gaps between them must be imitated in a different way. This is achieved by adding dye between the gold (aluminum) surface and the polycarbonate layer. In the initial state, the dye level is transparent and allows the laser beam to freely pass through it and be reflected from the gold (aluminum) coating. During recording, the laser goes into high power mode (8-16mW). When a laser hits a dye, it heats it, destroying chemical bonds, and forms dark, opaque spots. When reading with a 0.5 mW laser beam, the photo detector detects the difference between burnt spots and intact areas. This difference is interpreted in the same way as the difference between recesses and flat surfaces on regular CDs.

Over the long history of FixInfo, it’s even hard to imagine how many times our specialists answered questions regarding storage media and storing data on them. Almost every day we hear: “What kind of hard drive should I buy now so that I don’t have to recover data from it?”, “Advise a reliable flash drive that will not break in a month like the previous one.”, “Maybe it’s better to buy external drive in a rubber case, so that he is not afraid of falls like the old one? ”,“ Is it true that SSDs do not break, because they do not contain moving parts like regular HDDs? ”and so on. Such questions addressed to us are quite natural, because our main area of \u200b\u200bactivity is data recovery from hard drives, flash drives, RAID arrays and any other storage media.

For all the time tens of thousands of failed systems passed through our hands various carriers information, most of which, of course, were all kinds of hard disks, USB flash drives and memory cards. The vast experience of information recovery, accumulated statistics of breakdowns and causes of data loss allows us to confidently assert that absolutely reliable storage devices do not exist in principle. Most users think differently.

For some reason, many are convinced that if HDD drive the manufacturer has written about 500,000 hours of MTBF, it will be so. Most people do not doubt the reliability of flash drives and SSDs, because according to their beliefs, due to the lack of moving parts in them, they are simply unkillable. Almost every first customer is sure that an external drive in a rubber case will save his data from any crashes and other adversities. And advanced users think that important data can be trusted without problems with a RAID array or external NAS storage with this function. But, firstly, serious problems also happen to them, and secondly, RAID does not save from all kinds of logical problems. All these physical characteristics and manufacturers' promises do not cost anything. Of course, in different situations, operating or storage conditions, different types of media can differ significantly in physical durability or data storage periods.

You will probably be very disappointed to learn about the lack of a reliable information storage device, but unfortunately this is true. In fact, if you think a little, then everything is elementary, because there are countless reasons for data loss. First, you need to clearly understand that any electronic device will fail sooner or later. This can occur due to mechanical stress, external harsh operating conditions, wear of parts or memory cells, microcode errors or production defects. Imagine that you will simply lose a hypothetical reliable disk or accidentally format it and write down new information there, which we also encounter quite often. In such cases, data will be lost even if the hard drive is three times reliable.

Knowing all this and daily encountering all kinds of, and sometimes even unbelievable reasons for data loss, FixInfo experts always advise you to make backup copies first of all, and not try to find a reliable device. That is why our customers almost never need to restore data again. At the moment, data carriers are becoming more capacious, cheaper, but at the same time they are breaking much faster and it is unlikely that the trend will change in the near future.

Information storage was a very important moment in the development of mankind. People are constantly faced with a situation where information storage devices are outdated along with its contents. In the zero years, mankind transferred video and audio materials from audio tapes and VHS to CDs, flash cards. seemed like an untouchable data archive. Only after a while it became clear that if the film does not dry on the cassette, this does not mean that the information will remain and will exist forever: someone scratches the disks, someone loses the flash drive, and winchesters generally dry out over time. Therefore, leading software developers around the world are engaged in the implementation of the task of safe and long-term storage of information.

It is worth noting that the storage of personal data on a third-party server, in virtual space, is always fraught with the fact that third parties will have access to it over time

And if you create an archive of the necessary data on a hard drive, then third-party access to this data depends solely on the owner of the drive, on how reliable a storage location will be chosen.

Popular storage options for today

. This storage option is suitable for those who do not have constant access to the network and those who worry that the data will be safely hidden from third-party interference with the content. When choosing a reliable external creation of an archive of documents, photos or videos, you should not use a local working disk, since there is a probability of failure of such a device - with a constant load, the screw may not last for a long time, the OS will fly off or it will burn out. For long-term storage it is better to use SSD usb drives, which have an impressive amount of storage, a well-thought-out algorithm for managing file recording cells. And they won’t take up much space in the safe.

Before sending a good portion of information for storage for a long time, it must be properly preserved.

Many utilities have been developed for this, the most common of which is WinRAR.

This program creates archives for long-term data storage. Plus, it contains a function for compressing the file structure. It’s easy to organize files with her. Such training is carried out regardless of which device the data is stored on. Even if the information is supposed to be stored on a remote server, uploading one archive is much easier than uploading dozens of small files or one impressive file size.

After archiving the data, you need to prepare a device for storing information on which archive data will be placed. .

First of all, the hard drive needs to be formatted and defragmented.

Formatting is comparable to a situation when putting things in a bag, you shake it out, clean it.

Formatting does the same, only with a hard drive. When formatting, several options will be offered - how to structure files. NTFS or FAT32. It is preferable to choose the second one (if there are no startup files or OS files on the screw).

Defragmentation in the physical sense transfers the filled memory cells to the beginning of the disk, thereby leaving room for the screw to disperse when reading information in the future.

Flash drive. Flash drives are a convenient device for storing data. And, according to most, cheap. The advantages are that the use of FLASH is available on almost all modern devices - 90% of data processing equipment is equipped with USB ports around the world - from car radios to televisions.

The process of preparing the archive files and the drive itself is no different from the preparation described in paragraph 1.

The disadvantage of this storage device is that it is small in size and you can easily lose it. Such external devices for storing information are convenient in transportation or transfer from one user to another without the participation of electronics. Types of flash drives differ in two main parameters - the presence of shockproof shell and data transfer rate (2.0 or 3.0).

CD and DVD. Long-term storage in a designated place where they are not exposed to mechanical damage is an acceptable option for storing information. With the materials recorded on them, nothing will happen over time. But in order to write data to such media, it is necessary to use utilities. In the latest developed operating systems, the recording function is implemented at a basic level.

New ways of storing information appear every year. And everyone can choose the one that suits him. It is better to store photos electronically on the cloud - these are several interconnected servers that are specifically designed for this.

Service cloud storage provided by most popular social networks, giant corporations in the field of IT. Store photos on external media it is not always convenient when they need constant access from various places.

Often, information storage facilities are provided remotely, such as by Yandex, whose service is called Yandex.Disk

There are many similar services, but each of them has its drawbacks. Every developer or company as a whole must make money, so nothing happens absolutely free.

The well-known DropBox service provides convenient access to the server around the clock at the request of the user, but at the same time limits the space that the user can use

Provided that the user of this service will attract third parties, his disk space multiplies.

Modern means of information storage cannot provide comfortable access to the necessary data for a long time.

Anything can happen with sites, servers, so the idea of \u200b\u200bstoring data on external devices should not be left behind. hard choice drive or flash drive should be deliberate and balanced

M-disk

Storage of information is a guarantee that future generations will change the current state of society for the better. To make the future better, the present must be preserved. The developers of one of the projects created a fundamentally new medium that looks like an ordinary one dvd disk. Its fundamental difference is that information can be stored on it for more than a thousand years. Even the most reliable hard drives cannot boast such a temporary guarantee. Such a long period of time will provide an opportunity to analyze data after several centuries without loss of quality. It is practiced in modern society to create temporary capsules where M-disk is invested. Now these discs are available for sale and its average price is three dollars. No computer today will give confidence that the information recorded on it will last a dozen centuries.

In conclusion, we can say that none of the methods guarantees the eternal safety of information, and justify hopes for the infinitely long use of devices, but science is moving and allows you to create more and more new developments in this field. Save the story and pass on knowledge today to future generations, store photos, pictures, songs or digital passwords - never mind. The main thing is to store archives on such devices so that information will be used in the future.

Summary List of Storage Options

We summarize so that you can make the right choice of device or method of storing information. Let's go through the agreed points again:

When choosing a device for long-term data storage, you need to determine the type of this data. Recommendations on which files are best stored.

It is better to store family photo archives on disks that are not intended for rewriting, because there are often cases when, by pure chance, very necessary photos are erased. Every user came across this. It is not possible to recover data from a CD or DVD-RW. These are materials that cannot be restored under any circumstances - it is impossible to download images from the nineteenth century on the Internet, if only nobody posted them at the time of creation. Such suits should be stored “under the pillow” or in the same place where photo albums are stored.
Documents are files that are much smaller than media, so they are recorded on a flash card, which is prohibited from overwriting using auxiliary programs. Working with a flash drive is much more convenient than with an optical drive, regardless of its format. Just do not forget about the mechanical damage to the device, which can permanently destroy the information recorded on the media.
A collection of music or videos is more convenient to store on your hard drive, because this is the file format that is accessed regularly. Constantly connecting an external device is inconvenient, and on the screw files around the clock in the public domain.
It is better to store the materials that users use on the cloud so that they have access to online access points located at a distance from each other. Keep in mind that when disconnecting from the network at the time of editing files, it is regularly created backup copy, which is restored when the connection is resumed. For users, the obligatory registration in such services becomes a negative argument. Few people like to leave contact information in order to use one or another service.

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Now you know all the ways to store information. Ask questions to specialists.

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