There are information storage devices implemented in the form electronic circuits, and information storage devices, with the help of which data is recorded on any medium, such as magnetic or optical (previously, even paper media - punched cards and punched tapes - were used). Devices that are electronic circuits have a short data access time, but do not allow storing large amounts of information. On the contrary, information storage devices make it possible to store large amounts of information, but the time it takes to write and read it is longer.
Methods for storing bits in modern computers. Storing a bit in a machine requires a device that can be in two states, such as a switch (on or off), a relay (open or closed), or a flag on a flagpole (raised or lowered). One of the states is used to denote 0, the second to denote 1.
Trigger is a circuit whose output has a value of 0 or 1, and this value remains unchanged until a momentary pulse emanating from another circuit causes it to switch to another value. Thus, the trigger can be in one of two states, one of which corresponds to storing a binary zero, the other to storing a binary one.
A modern way of storing bits is also capacitor, which consists of two small metal plates located parallel to each other at some distance. If a voltage source is connected to the plates: the positive pole to one plate, the negative pole to the other, the charges from the source will transfer to the plates. Now, if you remove the voltage source, the charges will remain on the plates. If you connect the plates, then there will be electricity, and the charges will be neutralized. Thus, a capacitor can be in one of two states (charged and discharged), one of which can be taken as 0, the other as 1. Modern technologies make it possible to create millions of tiny capacitors combined into one circuit on one wafer (microcircuit, chip) ). Therefore, a capacitor has become a common way to store bits in machines.
Triggers and capacitors are examples storage systems with different degrees of stability. The trigger loses the entered data after the power is turned off. The capacitor's charges are so weak that they tend to dissipate on their own, even when the machine is turned on. Therefore, the charge on the capacitor must be constantly replenished using a so-called regeneration circuit. Because of this instability, computer memory built in this way is often called dynamic memory.
1.3.2. Memory.
Types of memory are shown in Fig. 1.2. Inner memory consists of operational and permanent storage devices.
Rice. 1.2. Types of computer memory.
Purpose random access memory– storage of data that may be required in the near future. Random access memory (RAM), which is often also called random access memory, is where programs that are executed in the this moment. This means that when you run any computer program located on the disk, it is copied into the RAM, after which the processor begins to execute the commands set out in this program. A part of RAM called "video memory" contains data corresponding to the current image on the screen. When the power is turned off, the contents of the RAM are erased. The performance (operating speed) of a computer directly depends on the size of its RAM, which in modern computers is usually Gigabytes. In the first IBM PCs (1981), the maximum volume random access memory was equal to 640 KB.
Memory structure. The storage circuits in a computer's RAM are organized into manageable units called memory cells, wherein standard cell size is eight bits or one byte. It is convenient to design RAM in which the total number of cells is a power of two. Small computers used in household appliances such as microwave ovens may contain only a few hundred RAM cells, while large computers used to store and process huge amounts of data may contain billions of RAM cells in their RAM. .
The relationships between memory measurement units are presented in Table 1.2.
Table 1.2. Units of measurement of computer memory.
|
Contains a byte |
Contains KB |
Contains MB |
Contains GB |
|
|
1073741824(2 30) | ||||
Although the concepts of "right" and "left" do not apply to the internal structure of a machine, it is generally believed that the bits within a memory cell are arranged in a row. The last bit of the left end is called the most significant bit, because if the contents of the cell is a number, then this bit will be its most significant bit. Also, the bit located at the right end is called the least significant bit.
In order to identify cells in RAM, each of them is assigned a unique name, which is called address. It is believed that the memory cells are arranged in a row and numbered in order, starting from zero. This addressing system not only makes it possible to uniquely identify a memory cell, but also organizes them, allowing expressions such as “next cell” or “previous cell” to be used in relation to them.
An important consequence of the fact that both RAM cells and the bits within each cell are ordered is the fact that all the bits in RAM are essentially lined up in a long row. Therefore, parts of this row can be used to store sequences of bits that are longer than the length of a single memory cell. In particular, even if the memory is divided into 1-byte cells, we can store a string of 16 bits in two consecutive cells.
Another consequence of representing RAM in the form of ordered cells with an address is the possibility of individual access to each cell, that is, data stored in the computer's RAM can be processed in a random order. This explains why RAM is often called random access memory (RAM - Random Access Memory). Random access to small data units(minimum is one byte) - a fundamental difference between RAM and data storage devices, which are discussed below and in which long sequences of bytes must be processed as a block. When RAM is built using dynamic memory technology (capacitors), it is called dynamic random access memory (DRAM - Dinamic RAM).
To fill RAM, the circuitry that actually stores the bits is combined with the circuitry needed to allow other circuitry to store and retrieve data from the memory cells. Thus, other circuits may obtain data from memory by requesting the contents of a cell at a specific address (a read operation), or they may write information to memory by requiring that a certain sequence of bits be placed into a cell at a specific address (a write operation).
Cache memory– this is a portion of high-speed memory (several kilobytes), the response time of which is approximately equal to the response time of the registers. It is often located in the central processing unit. In cache memory, the machine stores a copy of the part of RAM that is currently in use. In this case, data transfer, which is usually carried out between registers and RAM, occurs between registers and cache memory. All changes are then transferred to RAM, but at a more appropriate time.
ROM and external memory.
Due to power dependence (resets when power is removed) and limited RAM size, most machines are equipped with a mass storage system, which includes magnetic disks, CDs and magnetic tapes. The main differences between data storage devices and RAM are their independence from power supply, large capacity and, in most cases, autonomy, that is, the ability to move the storage medium independently of the computer, which is convenient for creating archives.
The main disadvantage of data storage devices is that they require mechanical movement and hence have a long response time compared to the machine's RAM, which is electronic.
Magnetic disks– a thin rotating disk with a magnetic coating. Recording information on them is based on the ability of some materials containing iron to retain magnetization after short-term exposure to a magnetic field. Binary zeros and ones are recorded on the ring-shaped tracks of the disk in the form of two differently magnetized areas. Read/write heads are located above and/or below the disk so that when the disk rotates, the head traces a ring on the disk's surface called a track. The tracks are divided into arcs, which are called sectors (the information is written on them as a continuous sequence of bits of 512 bytes in size). The capacity of a disk drive depends on the number of disks (surfaces) used and the density of tracks and sectors. Dividing a disk into tracks and sectors is called formatting the disk.
High-capacity disks, capable of storing gigabytes of information, consist of 5 to 10 hard drives mounted on a common spindle. The device is called hard drive (hard drive). For greater rotation speed, the read/write heads in these devices do not come into contact with the disk, but “float” above its surface. The hard magnetic disk is located inside the computer. A computer may have a package of (several) hard drives.
The floppy disk is floppy disk.
CDs– discs consisting of reflective material coated with a transparent protective layer. Information is recorded on them by changing the structure of their reflective layer. Information is extracted from the disk using a laser beam, which monitors differences in the structure of the reflective layer of the disk as it rotates. Information on CD-DA format discs (capacity 500-700 MB) is stored on a track similar to the spiral groove of a gramophone record. The DVD format has a capacity of up to 10GB.
Magnetic tapes– information is recorded on a magnetic layer of thin plastic tape, which is wound onto a reel for storage. Used for offline data storage (archive).
Flash drive– a data storage device containing an electronic non-volatile memory chip.
Information on media is stored in the form files. The file is treated as one multi-bit block. A file is an area on a magnetic disk, the smallest unit of information storage, containing a sequence of bytes and registered by the operating system under its unique name. A unique file name consists of a name and an extension (file type). The file type cannot be changed arbitrarily. Parameters characterizing the file (properties): 1) full file name; 2) file size in bytes; 3) date of file creation; 4) time of file creation; 5) file attributes, which determine the degree of access to the file.
Logical drive- this is either the entire disk or a part of the disk designed to store a certain amount of information. A logical drive is designated by a capital letter followed by a colon. A computer may have access to several hard drives, floppy disk drives, and CD-roms. Each of them can be a separate logical drive, but some hard drives can be divided into parts, each of which is a separate logical drive. The computer treats each logical drive as a separate device, although in reality it may only represent a portion of the actual (physical) disk and even a portion of RAM.
Catalog(directory, English directory) (folder) - part of a logical disk designed to store a certain amount of information (in the form of files). A directory can include several other directories (subdirectories) and be part of another directory (superdirectory). The logical drive is also the highest level directory - the root directory. Thus, a directory system with a tree-like (hierarchical) structure is formed on the disk.
Structure of information processing on a computer as follows. When entered, it is encoded with ones and zeros, i.e. bits, then processed by bytes. If it is necessary to save information, it is “packed” into files. When accessing files, the reverse process of transition from a code form to a natural and understandable one (decoding information) occurs.
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Storing information on a personal computer
A computer is a device that is specifically designed to work with information.
Random access memory is memory designed to temporarily store data and instructions necessary for the processor to perform operations. RAM is manufactured in the form of memory modules (flat plates with electrical contacts, on the sides of which large integrated circuits memory). RAM modules have a large number of indicators (type, type, timings, frequency) that significantly affect memory performance.
During operation, the computer's memory accesses one of two types of so-called “storages” of information. Volatile memory of a computer - RAM (Random Access Memory) - is a storage of information that must be constantly updated in order to store miscellaneous information, which is currently necessary for the computer to operate. It is automatically cleared when the computer is disconnected from power.
Computer static memory - ROM (Read Only Memory) - is an information storage device designed to be unchangeable and long-term storage files that should remain in the computer's memory after the computer is disconnected from the power supply.
External (long-term) memory is a place for long-term storage of data (programs, calculation results, texts, etc.) not currently used in the computer’s RAM. To work with external memory It is necessary to have a drive (disk drive - a device that provides recording and reading of information) and a storage device - media. Devices are usually divided into types and categories in connection with their operating principles, operational, technical, physical, software and other characteristics.
Flexible magnetic disks. Removable magnetic disks (floppy disks) are inserted into the computer through a special slot system unit– disk drive. In fact, this is not one disk, but a group of disks that have a magnetic coating and rotate with high speed. The main parameters of floppy disks are: technological size (measured in inches), recording density (measured in multiples of units) and total capacity.
Hard magnetic disks or HDDs, hard drives, are the main storage of large-volume information, based on the principle of magnetic recording, hidden inside the case of the system unit. It is the main data storage device in most computers. Information in HDD is recorded on rigid plates coated with a layer of ferromagnetic material. The storage medium is combined with a storage device, drives, and an electronics unit and is usually installed inside the computer system unit.
External hard disks– dynamic data storage systems. They are convenient for doing business and provide freedom of creativity and interaction at any time, anywhere.
External HDD easy to use due to its portability, support high speed interface for fast data transfer.
Optical drives and disks. A collective name for storage media made in the form of disks, read from which is carried out using optical radiation. Disks are usually flat, their base is made of polycarbonate, on which a special layer is applied to store information. To read information, a laser beam is usually used, which is directed to a special layer and reflected from it.
Laser drives and disks. Laser drives (CD-ROM and DVD-ROM) use the optical principle of reading information. Laser CD-ROM (CD - CompactDisk, compact disc) and DVD-ROM (DVD - Digital Video Disk, digital video disc) disks store information that was recorded on them during the manufacturing process. It is impossible to write new information to them, which is reflected in the second part of their names: ROM (ReadOnlyMemory - read only). Such discs are produced by stamping and have a silver color. On CD-RW and DVD-RW (RW – ReWritable) discs, which have a “platinum” tint, information can be recorded many times.
First generation optical disks: laser disc, compact disc, magneto-optical disc.
Second generation optical discs: DVD, MiniDisc, Digital Multilayer Disk, DataPlay, Fluorescent Multilayer Disc, GD-ROM (Compact Disk Read-Only Memory), Universal Media Disc.
Third generation optical discs: Blu-rayDisc, HDDVD, Forward Versatile Disc, Ultra Density Optical, Professional Disc for DATA, Versatile Multilayer Disc.
Fourth generation of optical discs: HolographicVersatileDisc, SuperRensDisc.
Flash memory. Flash memory is a non-volatile type of memory. It is a microcircuit housed in a miniature flat housing. To read or write information, the memory card is inserted into special drives built into mobile devices or connected to a computer via a USB port. Flash memory cards do not have moving parts, which ensures high data safety when used in mobile devices(laptop computers, digital cameras, etc.). There are a huge variety of them: SD, MMC, CompactFlashType I and II, MemoryStick, MemoryStickDuo, TransFlash, miniSD, microSD, RS-MMC, SmartMedia, MiniDisk, etc.
CompactFlash is perhaps the oldest flash memory: the first copy was released back in 1994 by SanDisk. There are two types of CompactFlash cards: CF Type I, CF Type II, and they differ only in the thickness of the case.
SD (SecureDigital) - was also created through the efforts of SanDisk, Panasonic and Toshiba. These cards use cryptograms (data encryption) to protect data from unauthorized copying or overwriting.
MMC (MultiMediaCard) is the result of the work of SanDisk and Siemens. Each MMC has its own memory controller. At the same time, the thickness of multimedia cards is almost a third less than that of the “spy” brother, which allows the use of MMC drives in various miniature devices.
RS-MMC (ReducedSize MMC) – also known as MMCmobile. They differ from MMC only in their reduced size and are mainly used in mobile phones.
Memory Stick Duo is an evolution of Memory Stick itself. The size and power consumption of the cards have decreased, but at the same time the maximum capacity has also decreased. Otherwise it is completely similar to regular MS.
SmartMedia is a standard that was developed by Toshiba back in 1995. Features this standard can be considered very low power consumption and the absence of its own controller, the operating speed is extremely low and the maximum memory amount is only 256 MB, which is negligible by today's standards, especially considering the size of the card
XDPicture (ExtremeDigital) - were created by FujiFilm and Olympus to replace the outdated SmartMedia format. These cards are used primarily in digital cameras from these companies.
Also recently, USB flash drives (flash drive, USB drive, USB disk) have become widespread, practically replacing floppy disks and CDs.
Storing information online
The Internet is the connection of computers around the world into a single information network. In another way, the Internet is called the global computer network.
To connect computers, regular telephone lines and a modem device are used. The modem converts the information into a form suitable for transmission over the telephone.
Thus, information stored around the world becomes available to anyone with a computer, telephone and modem.
Telephone communications is not the only way to connect computers. Much faster information transmitted via optical cables and radio communications. These channels are gradually replacing telephone connections on the Internet.
You can find an answer to almost any question on the Internet. Read the latest newspaper, go to the library, book plane tickets, buy goods, make pen pals.
We know that programs and data in a computer are stored on the hard drive in the form of files.
File is a certain amount of information that has a name and is stored in long-term (external) memory.
File name is a sequence of characters that allows the user to navigate file system. The file name consists of two parts, separated by a dot: the proper name of the file and an extension that determines its type. A custom file name can contain from 1 to 255 characters. In addition to Latin, the use of the Russian alphabet is allowed.
An extension is a combination of letters and numbers ranging from one to three characters in length, which complements the name itself, but more often indicates the format and type of data stored in the file. It is separated from the actual file name by a dot and is an optional part of it. Extensions are used to identify the type (format) of a file. With their help, the user and software The computer can determine the type of data stored in the file.
The extension is usually specified in the form *.rar, i.e. an asterisk and a dot are added before the extension characters, where the asterisk symbolizes any file name.
The extension can indicate not only the type of information that is stored in the file (image, media file, text file), but also on the way this information is encoded. For example, *.gif, *.jpg, *.bmp, *.raw, *.png, etc. are extensions of image files, but the ways of encoding images in such files are different, and not every program that opens one type will be able to open another.
There are files that do not have an extension, usually this is system files.
The file is opened by the program in which it was created, or universal program.
Examples of file extensions different types:
*doc, *, xdoc, *.rtf, *.txt, *.pdf – text documents(the contents of such files are text and they are opened in a program for working with text - Letter.doc, Catalog.xls, text.txt).
*.jpg, *.gif, *.jpeg, *.bmp, *.raw, *.png, *.emf, *.ico, *tif, *.tiff, *.jp2, *.pcx, *.tga , *.wbmp – graphic image(photos and pictures – Figure.gif, Nature.tif, Photo.jpg, Figure.bmp).
*.html, *.htm, *.xhtm – Internet page (Book.htm, Windows.hlp, Book.html).
*.exe, *.com – executable file (contain programs ready for execution – ACDSee9.exe, Command.com).
*.rar, *.zip, *.7z – zipped file (Abstract.zip, Abstract.rar).
*.avi, *.mpeg, *.mpg, *.mkv, *.3gp, *.mp4, *.wmf – video file extensions (the contents of such video files and they open in players – Clip.avi, Film.mpeg).
*.mp3, *.mp2, *.wave, *.wav, *.amr, *.wma, *.aac, *.ogg, *.midi, *.mid, *.kar – audio file extensions (music file and you need to open it in the player program - Song.mp3).
Files with similar content or the same purpose can be placed in folders (directories). Directories (folders), in turn, can also be combined into directories. Thus, an ordered structure of files and directories is formed on the disk, which allows you to quickly find the necessary information. This structure is called a file system.
File system - part operating system for storing files and organizing directories, which is necessary for orderly placement of data and programs in external memory.
The file structure can be multi-level or single-level.
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Practical lesson No. 6-2 Topic: A file as a unit of information storage on a computer. File attributes and size. Accounting for file volumes during storage and transmission.
Practical lesson No. 6-2
Topic: A file as a unit of information storage on a computer. File attributes and size. Accounting for file volumes during storage and transmission.
Number of hours: 1
Purpose of the lesson: to take into account the volume of files during their storage and transmission.
Assignment: Familiarize yourself with the theoretical principles on this topic, complete the tasks of the practical lesson, and formulate a conclusion.
The report must contain:
1. Title of the work
2.Purpose of work
3. Results of task 3, 4, 5
4. Conclusion on the work (it is necessary to indicate the types of work performed, goals achieved, what skills and abilities were acquired during its implementation)
Guidelines for implementation:
1. Brief theoretical information
A file is a certain amount of information, with a name, stored in the long-term memory of a computer.
The file name is divided into two parts by a period: the file name (prefix) and the extension (suffix), which determines its type (program, data, etc.).
The file name is given by the user, and its type is usually set automatically by the program.
The file system is a functional part of the operating system that allows operations on files. The file system allows you to work with files and directories (directories) regardless of their content, size, type, etc.
The file system defines the general structure for naming, storing, and organizing files in the operating system.
Hierarchical file system:
Various operations can be performed on files:
Copying (a copy of the file is placed from one directory to another)
Move (the file itself is moved to another directory)
Delete (the file entry is removed from the directory)
Renaming (file name changes), etc.
Rules for creating a file name: 1. You cannot use the following characters, which are reserved for special functions: ? . , ; : = + * / \ “ | SPACE
2.The following characters cannot be used in long names:? : * / \ “
2.Task
Task 3. Suggest names and types for the files listed below. Copy the table into your notebook and fill it out.
| Full file name |
|||
| Photo of my family | |||
| Apple Pie Recipe | |||
| Booklet "My College" | |||
| Open letter to Bill Gates | |||
| Family album “My Pedigree” | |||
| Reproduction of Malevich’s painting “Black Square” | |||
| Petition to the college director to increase the number of computer science lessons | |||
| Abstract on history | |||
| Article in the journal “Informatics and Education” |
Task 4. Suggest options for programs that open files with a particular extension. Draw the table into your notebook and fill it out.
“unsatisfactory” - less than 45%.
Task 5. Complete the tasks in your notebook.
Come up with a name for a text file that will contain information about your home. Underline your own file name.
Come up with a name graphic file, which will contain a drawing of your house. Underline the file extension.
Write it down in one column correct names files, and in the second the correct directory names:
Letter.18, letter.txt, WinWord, letter.doc, College?12, My documents, rose.bmp, crop12.exe, 1C, red.com
3. Questions for self-control:
What are the main capabilities of archivers?
What is an electronic archive?
What is the point of unzipping?
How to set the file name?
What is a file system?
What is a hierarchical file system?
What operations can be performed on files?
Astafieva N.E., Gavrilova S.A., Tsvetkova M.S. Informatics and ICT: Workshop for professions and specialties of technical and socio-economic profiles / ed. M.S. Tsvetkova. - M.: 2014
Criteria for assessing completed practical assignments
Each task is scored 5 points (maximum), in accordance with the requirements
Overall rating is displayed based on the total points for each solved problem (5*5=25 points)
In total, completed practical work can be graded from 0 to 100%, and then the assessment of the student’s knowledge will be as follows:
“excellent” - 86 – 100%,
“good” - 66 – 85%,
“satisfactory” - 45 – 65%,
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Units of measurement of information, files, folders and data storage formats » Video courses, useful software and educational computer articles
In this article we will talk about units of measurement of information, files, folders and data storage formats.
Understanding the basic principles of placing and measuring information will allow you to easily manipulate files and folders and will not cause any difficulties when performing basic tasks.
Units of information
Bit (English bit - a little) is a unit of measurement of information.
Byte (English byte) is a unit of measurement of the amount of information; by default, a byte is considered equal to eight bits.
1Byte = 8Bits
Basically, depending on the volume, the first three units of measurement are used: Calobytes, Megabytes, Gigabytes.
A little later in this article we will look at specific examples of how much space certain files take up.
Before that, let's look at one of the main concepts associated with measuring and storing information.
A file is a named memory area in which a certain amount of information can be stored.
Each file has a number of properties:
The file name is a sequence of characters.
File name extension is a sequence of characters that continues the file name through a dot, for example document.DOC, each program has files with a specific extension.
So what is a computer? There may be many answers. They can be different from: - “Box with a screen and buttons”, “Human’s friend and assistant” or “Smart machine”. These answer options are not entirely accurate. A computer cannot be “smart” or “stupid”. He cannot treat you like a friend or shower you with unfriendly electric sparks. Just as a hammer or a calculator cannot be “smart” or “stupid”.
The most accurate answer to this question would be “A tool for processing information.” Therefore, you need to treat the computer as a tool that you have the power to use for good or harm.
All information on a computer is stored in the form of files. The file can be text that you type in a text editor and a program (" text editor") with which you type this text.
File – a named area on the hard drive (a program or document stored on the hard drive). Each file must have a unique (i.e. non-repeating) name. The full file name consists of a name and an extension. Extension – three letters added to the file name separated by a dot, without spaces, and indicating the type of information stored in the file. When specifying a file name, the following restrictions must be taken into account: - the file name must consist of letters, numbers and the symbols “-” (dash) and “_” (underscore). When specifying a name in a DOS environment, the length of the name (excluding extension) is limited to 8 characters, in Windows environment– 256 characters.
To work normally with a computer, it is necessary to understand exactly where our information is located. When we carry out any work, the information with which we work is located in the computer's memory. If we turn off the power, all information will be lost. In order to save information for later work, it is written to a hard drive in the same way as putting a sheet of paper in a folder.
Folder (directory) – a place to store files and other folders. All folders located on the computer form a catalog system.
A directory system is a collection of directories and the files and other (nested) directories stored in them. A method of graphically representing a directory system, in which directory branches emerge from the source disk, followed by branching of subdirectories, is called a directory tree. The source drive of a directory tree is called the root. When designating the root of a disk, indicate the full name of the disk and the sign “” (slash)
LECTURE
Plan:
1.1. Read-only memory (ROM)
1.2. Random Access Memory (RAM)
1.3. External storage device (ESD)
2. LMD drives
3. Drives on GMD
4. Drives for working with laser (optical) discs
5. Streamer
In this lecture we will talk about the types of computer memory and computer storage media.
Generations of computers are determined not only by the element base, processors and memory. Their capabilities, and in many ways their appearance, seriously depend on the storage media.
1. MEMORY, or STORAGE DEVICES (STORAGE)
There are three main types of computer memory: permanent, operational And external storage devices (ROM, RAM, VZU).
Purpose. Computer memory is designed to store information (programs, data and control commands).
Principle of operation. Numbers, symbols, commands are stored in memory on an equal basis and can be located in any memory cell. They are written to memory and read from memory along the same channels, using the same principle. For memory, the meaning of the encoded information does not matter. It is only important that the code has a certain number of bits. The length, or bit depth, of a cell is determined by the number of binary digits in the code. Each bit in the code can take the value 1 or 0.
In modern computers, the minimum addressable unit of information is a byte (8 bits), and the cell length is a multiple of 8. The cell length can be 2 bytes = 16 bits, 4 bytes = 32 bits, 8 bytes = 64 bits. The cell length is equal to the maximum number of bits that the processor can process or transmit simultaneously. The address of a cell is equal to the address of the least significant of the bytes included in it.
Under recording data memory refers to the placement of code in a cell at a specified address. In this case, the previous value located in this cell is erased. Newly written value stored in mind until new information is written to the cell. This rule is called rule for storing information.
Under reading (by reading) data from memory means sampling binary code from a cell with a specified address. In this case, a copy of the code is transferred from memory to the required device, and the value of the cell itself does not change.
Shippinginformation means that information is read from one cell and written to another cell. After the transfer process is completed, the same value will be stored in these two cells.
The cell address is formed in control device , then comes V address fetch device, which opens the information channel and connects the desired cell to write or read information.
Main user characteristics:
- capacity (volume)- number of bytes of memory. However, often a byte is too small a unit, so a system of larger units is used:
kilobyte (KB) - 1024 bytes = 2 10 bytes;
megabyte (MB) - 1024 KB;
gigabyte (GB) - 1024 MB;
- performance
- bit depth
Let's take a closer look at each of the listed types of computer memory.
1.1. Read Only Memory (ROM),
in modern terminology - ROM (Read Only Memory).
Principle of operation. In many PCs, the ROM is implemented as a separate chip, into which, when the PC is manufactured, the basic input/output commands are placed, which carry out the initial interaction between the PC hardware and software.
This type of memory is only available for reading the information stored in it.
After turning off the computer's power, the information in the ROM is retained, that is, the ROM - energy-independent device.
1.2. RAM
RAM, in modern terminology - RAM (Random Access Memory), an integral part of any PC. This is a high-speed memory of a relatively small volume (compared to the VSD), implemented in the form electronic circuit.
Principle of operation. RAM is available for both reading and writing information. It is in RAM that the program currently running on the PC and the data necessary for it are stored.
RAM operates under the direct control of the microprocessor, all data for which comes only from RAM.
RAM provides storage of information only during a session with a PC - after turning off the computer from the network, the data stored in RAM is lost forever, that is, RAM - volatile device.
The RAM capacity of modern PC models ranges from 640 KB (IBM PC XT) to 128 MB.
To speed up calculations, information from the most frequently used areas of RAM is placed into ultra-fast memory chips - cache memory . The lack of cache memory can significantly (20-30%) reduce the overall performance of the computer.
Currently, the cache memory used is from 64 to 512 KB.
1.3. EXTERNAL STORAGE DEVICE (ESD)
VRAM is intended for long-term storage of information and is characterized by a large memory capacity and low performance compared to RAM.
External computer memory is usually understood as a device for reading/writing information - STORAGES, and devices where information is directly stored - CARRIERS information.
As a rule, each storage medium has its own storage device.
In personal computers, such devices include:
Floppy disk drives designed for reading/writing information on floppy disks(floppy disks);
Hard magnetic disk drives, or hard drives;
Disk drives for working with laser CDs;
Streamers designed for reading/writing information on magnetic tapes;
Magneto-optical drives for working with magnetic optical discs.
Additional characteristic for this type of memory is access time, measured in nanoseconds.
The first storage media for computers were paper (punched cards, punched tapes). To work with them, there were two separate devices: a puncher - for recording information, a counter - for reading information and transferring it to RAM. Later, magnetic storage media (magnetic tapes, magnetic drums, magnetic disks) appeared, the drives of which combined both a reading device and a recording device. A device such as a hard drive combines both a storage medium and a storage device. For optical storage media (CDs, digital discs), drives can either combine read/write functions or be specialized - used, for example, for read-only.
2. HARD DISK STORAGES
HARD DISK STORAGES (HDD, or WINCHESTER) They are external storage devices in which the storage medium is hard non-removable magnetic disks combined into a package. .
Purpose. HDDs are designed for long-term storage of information constantly used when working with a PC: operating system programs, frequently used software packages, document editors, translators from programming languages, documents and programs prepared by the user, etc.
Currently, PCs without HDD are practically not produced. If the computer is included in the local computer network, then it can work without its own hard drive, but then it uses the central server's hard drive.
The hard drive is installed inside the system unit and externally is a sealed metal box, inside which there are several disks combined into one package, magnetic read/write heads, a mechanism for rotating the disk and moving the heads (Fig. 1).
| Rice. 1. Hard drive diagram |  |
hard drive:
capacity, that is, the maximum amount of data that can be written to the medium;
performance, determined by access time necessary information, its read/write time and data transfer rate;
uptime, characterizing the reliability of the device.
HDD capacity depends on the PC model. The first hard drive (early 80s) had a “colossal capacity” of 10 MB. It is believed that the volume of a modern hard drive should be at least 2-3 GB. The latest PC models have hard drives with a capacity of over 9 GB, and hard drives with a capacity of up to 20 GB are expected to appear.
Performance measured in milliseconds. For modern hard drives, access time is less than 10 ms.
Uptime usually 20 000 - 500 000 hours (that is, approximately 57 years).
Exist REPLACEABLE HARD DRIVES(and, accordingly, drives for them). They are mainly used for transferring large amounts of information between computers or for storing archival data. The main type is Jazz disc. Its capacity, depending on the model, is from 540 MB to 1.07 GB.
3. FLEXIBLE DISK STORAGES (FMD)
NGMD are external storage devices in which carriers information are removable magnetic disks (DISCETTES). Floppy disks allow you to transfer information from one PC to another, store it outside the PC, and create archival copies of texts and programs recorded on the hard drive.
The following types of floppy disks are currently in use:
Floppy disks with a diameter of 5.25 inches (5.25" - 133 mm) and capacity:
360 KB (marking - DS/DD);
1.2 MB (labeling - DS/HD);
Floppy disks with a diameter of 3.5 inches (3.5" - 89 mm) and capacity:
720 KB (DS/DD);
1.44 MB (DS/HD);
2.88 MB.
5.25" floppy disks are a thin plastic disk on which a magnetic coating is applied, similar to the coating of a magnetic tape, enclosed in a special dense envelope-case, which, however, is easy to bend. The disk is visible in the oblong cut on the envelope. The disk must not be touched hands, and the floppy disks themselves should be stored in a paper envelope, carefully inserted into the drive and prevent dust from getting on the floppy disk.
In 3.5" floppy disks, the disk is enclosed in a hard plastic case; there are no open parts of the disk on the surface of the floppy disk, so such floppy disks are more reliable and can be used without fear of damaging the surface of the disk itself (Fig. 2).
Before using it for the first time, the floppy disk must be prepared, format . This is done using special programs. When formatting programs work, special magnetic marks are applied to the disk, dividing the surface of the disk into tracks and sectors. After formatting, you can write information to the disk. Currently, floppy disks are sold already formatted.
| Rice. 2. Diagram of a 3.5" floppy disk |  |
There are floppy disks with a capacity of 100MB - ZIP DISCS . The drives for them are not built into the PC case, but are used as removable devices (mobile disk drives).
4. Drives for working with laser (optical) discs
CD-ROM drives(Compact Disk Read Only Memory).
Purpose. These drives are used to handle various types of compact discs (CDs).
Optical disk drives are divided into three types:
Non-writable (CD-ROM - read-only memory on a CD);
Write once and read many times (CD-WORM);
Rewritable (CD-RW, CD-E).
Principle of operation. At records The CD is processed by a laser beam (without mechanical contact), burning out the area that stores a logical one, and leaving intact the area that stores a logical zero. As a result, small depressions, so-called pits, are formed on the surface of the CD. At reading A laser beam of lower intensity is directed onto the surface of the disk, the characteristic of the reflected beam is analyzed, which is converted into a digital code.
Basic user characteristics CD-ROM drives:
capacity CD, which is 500-700 MB;
baud rate from the media to the RAM, depending on the drive it ranges from 150 to 4800 KB/s;
average access time, which the drive needs to find the necessary data on the media. Depending on the drive, it ranges from 80 to 400 ms.
As the technology for creating CDs and drives improved, the need arose to increase the capacity of optical storage media. DVDs (Digital Versatile Disk) appeared, used mainly for storing and playing video images. The capacity of such disks is from 4.7 GB to 17 GB. Information transfer speed - 1350 Kb/s. The duration of video playback is from 2 to 6 hours.
IN MAGNETO-OPTICAL SYSTEMS Magnetic recording is made on the surface of a compact disc, which is previously strongly heated by a laser beam. The first magneto-optical disks looked like a 3.5" floppy disk. Then 5.25" and 12" disks were created, which were also placed in plastic case. After this, magneto-optical discs appeared without a housing, that is, exactly the same as ordinary laser audio discs.
The capacity of magneto-optical floppy disks can be from 20 MB to 2 GB.
Information recorded on magneto-optical disks can be stored for up to 30 years, so, for example, archival data can be recorded on them.
5. STREAMER
Purpose. A streamer is a device for ensuring reliable long-term storage of large volumes of information, which is becoming increasingly popular and widespread among professional users. personal computers. They are used primarily for backup archiving of information in industry, publishing houses, banks, the business and scientific world.
Principle of operation. A streamer is a magnetic tape drive, a digital cassette recorder that uses special cassettes - tape cartridges that protect the storage medium from external influences.
Like any tape recorder, the streamer has a drawback: to find the right place on the tape, sometimes you have to rewind the entire cassette.
For streamer cartridges, a special high-quality magnetic tape is used, which uses especially clean, fine-grained magnetic particles, and the surface of the tape is carefully polished. This guarantees recording reliability and long-term storage of recorded data.
KNOW
Memory computer (storage device) designed to store information (programs, data and control commands).
Properties of storage devices (memory):
Information is stored in memory in binary code;
All memories consist of individual cells, each of which has its own address (starting from address zero).
Cell length modern computers is a multiple of 8. The cell length can be 2 bytes = 16 bits, 4 bytes = 32 bits, 8 bytes = 64 bits. The cell length is equal to the maximum number of bits that the processor can process or transmit simultaneously. The minimum addressable unit is a byte. The address of the cell is equal to the address of the lowest byte included in it.
Data recording to memory - placing the corresponding code in a cell at the specified address. In this case, the previous value located in this cell is erased.
Reading(reading) data from memory - sampling binary code from a cell with a specified address. In this case, a copy is transferred from memory to the required device, and the value of the cell itself does not change.
Forwarding information means that information is read from one cell And is written to another cell. Once the forwarding process is complete, these two cells will store the same value.
Rule for saving information: a value written to a memory cell is stored until new information is written to that cell.
Main memory characteristics:
capacity- number of bytes of memory;
performance- the time of accessing memory cells, determined by the time of reading or writing time of information. Measured in nanoseconds (10~9 s);
bit depth- the number of input/output lines that have RAM and ROM chips or external drives.
Types of PC memory are listed in Fig. 3.
In table 1 provides information about the VZU.
Table 1
External computer memory
1. Name the main information storage devices in a computer.
2. What are the main user characteristics of memory?
3. What is the purpose and principle of operation, the main characteristics of the ROM?
4. What is the purpose and principle of operation, the main characteristics of RAM?
5. What is the purpose and principle of operation, the main characteristics of the VSU?
6. What is the purpose and principle of operation, the main characteristics of the HDD?
7. What is the purpose and main characteristics of GMD?
8. What is the purpose, operating principle and main characteristics of a disk drive for working with laser (optical) discs?
9. What is the purpose and operating principle of the streamer?
RAM- memory designed for temporary storage of data and instructions necessary for the processor to perform operations. RAM is manufactured in the form of memory modules (flat plates with electrical contacts flanked by large integrated memory circuits). RAM modules have a large number of indicators (type, type, timings, frequency) that significantly affect memory performance.
During operation, the computer's memory accesses one of two types of so-called “storages” of information. Volatile computer memory – RAM (Random Access Memory)- this is an information storage that must be constantly updated so that it stores various information that is currently necessary for the operation of the computer. It is automatically cleared when the computer is disconnected from power.
Computer static memory – ROM (Read Only Memory)– this is an information storage designed for permanent and long-term storage of files that must be in the computer’s memory after the computer is disconnected from the power supply.
External (long-term) memory – This is a place for long-term storage of data (programs, calculation results, texts, etc.) not currently used in the computer’s RAM. To work with external memory, you must have a drive (disk drive - a device that allows you to write and read information) and a storage device - media. Devices are usually divided into types and categories in connection with their operating principles, operational, technical, physical, software and other characteristics.
Floppy magnetic disks . Removable magnetic disks (floppy disks) are inserted into the computer through a special slot in the system unit - the floppy drive. In fact, this is not one disk, but a group of disks that have a magnetic coating and rotate at high speed. The main parameters of floppy disks are: technological size (measured in inches), recording density (measured in multiples of units) and total capacity.
Hard magnetic disks or HDD, hard drive, – the main storage of large-volume information, based on the principle of magnetic recording, is hidden inside the case of the system unit. It is the main data storage device in most computers. Information in HDD is recorded on rigid plates coated with a layer of ferromagnetic material. The storage medium is combined with a storage device, drives, and an electronics unit and is usually installed inside the computer system unit.
external HDs– dynamic data storage systems. They are convenient for doing business and provide freedom of creativity and interaction at any time, anywhere.
The external hard drive is easy to use due to its portability and supports a high-speed interface for fast data transfer.
Optical drives and disks . A collective name for storage media made in the form of disks, read from which is carried out using optical radiation. Disks are usually flat, their base is made of polycarbonate, on which a special layer is applied to store information. To read information, a laser beam is usually used, which is directed to a special layer and reflected from it.
Laser drives and disks. Laser drives (CD-ROM and DVD-ROM) use the optical principle of reading information. Laser CD-ROM (CD - CompactDisk, compact disc) and DVD-ROM (DVD - Digital Video Disk, digital video disc) disks store information that was recorded on them during the manufacturing process. It is impossible to write new information to them, which is reflected in the second part of their names: ROM (ReadOnlyMemory - read only). Such discs are produced by stamping and have a silver color. On CD-RW and DVD-RW (RW – ReWritable) discs, which have a “platinum” tint, information can be recorded many times.
First generation of optical discs: laser disc, compact disc, magneto-optical disc.
Second generation optical discs: DVD, MiniDisc, Digital Multilayer Disk, DataPlay, Fluorescent Multilayer Disc, GD-ROM (Compact Disk Read-Only Memory), Universal Media Disc.
Third generation optical discs: Blu-rayDisc, HDDVD, Forward Versatile Disc, Ultra Density Optical, Professional Disc for DATA, Versatile Multilayer Disc.
Fourth generation of optical discs: HolographicVersatileDisc, SuperRensDisc.
Flash- memory. Flash memory is a non-volatile type of memory. It is a microcircuit housed in a miniature flat housing. To read or write information, the memory card is inserted into special drives built into mobile devices or connected to a computer via a USB port. Flash memory cards do not have moving parts, which ensures high data safety when used in mobile devices (laptop computers, digital cameras, etc.). There are a huge variety of them: SD, MMC, CompactFlashType I and II, MemoryStick, MemoryStickDuo, TransFlash, miniSD, microSD, RS-MMC, SmartMedia, MiniDisk, etc.
Co mpactFlash- perhaps the oldest flash memory: the first copy was released back in 1994 by SanDisk. There are two types of CompactFlash cards: CF Type I, CF Type II, and they differ only in the thickness of the case.
SD (SecureDigital)– was also created through the efforts of SanDisk, Panasonic and Toshiba. These cards use cryptograms (data encryption) to protect data from unauthorized copying or overwriting.
MMC (MultiMediaCard)– is the fruit of the work of SanDisk and Siemens. Each MMC has its own memory controller. At the same time, the thickness of multimedia cards is almost a third less than that of the “spy” brother, which allows the use of MMC drives in various miniature devices.
RS-MMC (ReducedSize MMC)– also known as MMCmobile. They differ from MMC only in their reduced size and are used mainly in mobile phones.
Memory Stick Duo– is an evolution of the Memory Stick itself. The size and power consumption of the cards have decreased, but at the same time the maximum capacity has also decreased. Otherwise it is completely similar to regular MS.
SmartMedia- a standard that was developed by Toshiba back in 1995. The features of this standard can be considered very low power consumption and the absence of its own controller, the operating speed is extremely low and the maximum memory amount is only 256 MB, which is negligible by today's standards, especially considering the size of the card
ХDPicture (ExtremeDigital)- were created by FujiFilm and Olympus to replace the outdated SmartMedia format. These cards are used primarily in digital cameras from these companies.
Also recently, USB flash drives (flash drive, USB drive, USB disk) have become widespread, practically replacing floppy disks and CDs.
Storing information online
The Internet is the connection of computers around the world into a single information network. In another way, the Internet is called the global computer network.
To connect computers, regular telephone lines and a modem device are used. The modem converts the information into a form suitable for transmission over the telephone.
Thus, information stored around the world becomes available to anyone with a computer, telephone and modem.
Telephone communication is not the only way to connect computers. Information is transmitted much faster via optical cables and radio communications. These channels are gradually replacing telephone connections on the Internet.
You can find an answer to almost any question on the Internet. Read the latest newspaper, go to the library, book plane tickets, buy goods, make pen pals.
We know that programs and data in a computer are stored on the hard drive in the form of files.
File– this is a certain amount of information that has a name and is stored in long-term (external) memory.
File name– a sequence of characters that allows the user to navigate the file system. The file name consists of two parts, separated by a dot: the proper name of the file and an extension that determines its type. A custom file name can contain from 1 to 255 characters. In addition to Latin, the use of the Russian alphabet is allowed.
Extension is a combination of letters and numbers from one to three characters long, which complements the name itself, but more often indicates the format and type of data stored in the file. It is separated from the actual file name by a dot and is an optional part of it. Extensions are used to identify the type (format) of a file. With their help, the user and computer software can determine the type of data stored in the file.
The extension is usually specified in the form *.rar, i.e. an asterisk and a dot are added before the extension characters, where the asterisk symbolizes any file name.
The extension can indicate not only the type of information that is stored in the file (image, media file, text file), but also the way this information is encoded. For example, *.gif, *.jpg, *.bmp, *.raw, *.png, etc. are extensions of image files, but the ways of encoding images in such files are different, and not every program that opens one type will be able to open another.
There are files that do not have an extension, usually these are system files.
The file is opened by the program in which it was created, or by a universal program.
Examples of file extensions of different types:
*doc, *, xdoc, *.rtf, *.txt, *.pdf – text documents (the contents of such files are text and they are opened in a program for working with text - Letter.doc, Catalog.xls, text.txt).
*.jpg, *.gif, *.jpeg, *.bmp, *.raw, *.png, *.emf, *.ico, *tif, *.tiff, *.jp2, *.pcx, *.tga , *.wbmp – graphic image (photos and pictures – Figure.gif, Nature.tif, Photo.jpg, Figure.bmp).
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