| Purpose and device of a computer. Computer memory

Lesson 6
Purpose and device of a computer. Principles of organizing internal and external memory

§5. Purpose and device of a computer
§6. Computer memory

Purpose and device of a computer

Main topics, paragraphs:

What do computers and humans have in common?
- what devices are included in the computer;
- what is data and program;
- von Neumann principles.

Questions studied:

What do computers and humans have in common?

With this lesson we begin our acquaintance with the computer. For computer science, a computer is not only a tool for working with information, but also an object of study. You will learn how a computer works, what work can be done with it, and what types of tools exist for this purpose. software.

Since ancient times, people have sought to make their work easier. For this purpose, various machines and mechanisms were created to enhance human physical capabilities. Electronic computer(in modern terminology - a computer) (Fig. 2.1) was invented in the middle of the 20th century to enhance the capabilities of human mental work, i.e., working with information.

From the history of science and technology it is known that man “spotted” the ideas for many of his inventions in nature.

For example, back in the 15th century, the great Italian scientist and artist Leonardo da Vinci studied the structure of the bodies of birds and used this knowledge to design aircraft.

Russian scientist N. E. Zhukovsky, the founder of aerodynamics, also studied the mechanism of bird flight. The results of these studies are used in aircraft design calculations.

Is there a prototype of a computer in nature? Yes! Man himself is such a prototype. Only inventors sought to transfer to the computer not the physical, but the intellectual capabilities of a person.

According to its purpose, a computer is a universal technical tool for a person to work with information.

According to the principles of its design, a computer is a model of a person working with information.

What devices are included in the computer?

Human information activity is divided into components:

Reception (input) of information;
remembering information (memory storage);
thinking process (information processing);
transmission (output) of information.

The computer includes devices that perform similar functions:

Input devices;
storage devices - memory;
processing device - processor;
output devices.

During computer operation, information enters memory through input devices; the processor extracts the processed information from memory, works with it and places the processing results into memory; The results obtained are communicated to humans through output devices.

Most often, a keyboard is used as an input device, and a monitor or printer (printing device) is used as an output device.

What is data and program

Still, one cannot equate the “mind of a computer” with the mind of a person. The most important difference is that the work of a computer is strictly subordinate to the program embedded in it, while a person controls his own actions.

Computer memory stores data and programs.

Data- This is processed information presented in the computer memory in a special form.

Program is a description of the sequence of actions that a computer must perform to solve a given data processing task.

If information for a person is the knowledge that he possesses, then information for a computer is data and programs stored in memory. Data is “declarative knowledge”; programs are “procedural knowledge” of a computer.

Von Neumann's principles

In 1946, the American scientist John von Neumann formulated the basic principles of the design and operation of computers. The composition of computer devices described above and the interaction between them is called von Neumann architecture. Neumann architecture is characterized by the presence of one processor that controls the operation of all other devices. You have yet to become familiar with other von Neumann principles.

Briefly about the main thing

Computer is a software-controlled device for performing any type of work with information.

The computer includes: processor, memory, input devices, output devices.

Stored in computer memory data and programs.

Computer works according to programs created by man.

Questions and tasks

1. What human capabilities are reproduced by a computer?

2. List the main devices included in the computer. What is the purpose of each of them?

3. Describe the process of exchanging information between computer devices.

4. What is a computer program?

5. How is data different from a program?

6. Prepare a report on the principles formulated by von Neumann.

Computer memory

Main topics, paragraphs:

Internal and external memory;
- structure internal memory computer;
- program in computer memory;
- media and external memory devices.

Questions studied:

A computer as a model of a person working with information.
- Scheme information exchange on the computer.
- Difference between program and data.
- Difference between internal and external computer memory.
- The principle of binary encoding of information.
- The structure of the computer’s internal memory, its properties.
- Media and external memory devices.

Internal and external memory

When working with information, a person uses not only his own knowledge, but also books, reference books and other external sources. In Chapter I “Man and Information” it was noted that information can be stored in human memory and on external media. A person can forget information that has been memorized, but records are stored more reliably.

A computer also has two types of memory: internal (RAM) and external (long-term) memory.

Internal memory- This electronic device, which stores information while powered by electricity. When the computer is disconnected from the network, information from RAM disappears. The program is stored in the internal memory of the computer during its execution.

The formulated rule refers to the Neumann principles. This rule is called the stored program principle.

External memory- these are various magnetic media (tapes, disks), optical disks, flash memory cards. Saving information on external media does not require constant power supply.

IN modern computers There is another type of internal memory called read-only memory - ROM. This is non-volatile memory, information from which can only be read.

Figure 2.2 shows the composition of computer devices. The arrows indicate the directions of information exchange.

Structure of the computer's internal memory

Computer devices perform certain work with information (data and programs). How is information itself represented on a computer? To answer this question, let’s “look” inside computer memory. The structure of the computer's internal memory can be roughly depicted as shown in Fig. 2.3.

The smallest element of computer memory is called a memory bit. In Figure 2.3, each cell represents a bit. You see that the word "bit" has two meanings: a unit of measurement of the amount of information and a particle of computer memory. Let us show how these concepts are related to each other.

Each bit of memory can currently store one of two values: zero or one. The use of two characters to represent information is called binary encoding.

Data and programs in computer memory are stored in the form of binary code.

One character of a two-character alphabet carries 1 bit of information.

One bit of memory contains one bit of information.

The bit structure determines the first property of the computer’s internal memory - discreteness. Discrete objects are made up of individual particles. For example, sand is discrete because it consists of grains of sand. The “grains of sand” of computer memory are bits.

The second property of the computer's internal memory is addressability. Eight consecutive bits of memory form a byte. You know that this word also denotes a unit of information, equal to eight bits. Therefore, one byte of memory stores one byte of information.

In the internal memory of a computer, all bytes are numbered. Numbering starts from zero.

Serial number byte is called its address.

The principle of addressability means that:

Recording information into memory, as well as reading it from memory, is carried out at addresses.

Program in computer memory

Several consecutive bytes of memory form a memory cell whose address is the address of the low byte, that is, the byte with the lowest number. Figure 2.4 shows the addressing principle using 4-byte memory cells as an example.

One memory cell can store one program instruction or element of data processed by the program (for example, a number). A machine program is a set of instructions located in successive memory cells (Fig. 2.5).

Program team consists of an operational part - the operation code and an address part - addresses for placing the processed data in memory. The opcode specifies the action performed by the processor upon command. The work of the processor is automatic execution sequence of program commands until its completion (stop commands).

External storage media and devices

External memory devices- These are devices for reading and writing information to external media. Information on external media is stored in the form of files. You will learn more about what files are later.

The most important external memory devices in modern computers are magnetic disk drives(NMD), or disk drives.

The principle of magnetic recording was invented in the 20s of the last century. Then acoustic tape recorders appeared, which made it possible to record speech and music on magnetic tape, and then play the recorded sounds. The first type of external memory devices on a computer were magnetic tape drives - analogues of acoustic tape recorders.

A modern NMD works similarly to a tape recorder. A binary code is written on the surface of the disk, covered with a thin ferromagnetic layer: the magnetized area is one, the non-magnetized area is zero. When read from disk, this record turns into zeros and ones in the internal memory bits.

A recording head is connected to the magnetic surface of the disk (Fig. 2.6), which can move along the radius. During operation of the NMD, the disk rotates. At each fixed position, the head interacts with the circular track. Binary information is recorded on these concentric tracks.

Another type of external media is optical discs (another name for them is laser discs). They use not a magnetic, but an optical-mechanical method of recording and reading information.

First came laser discs, on which information is recorded only once. It cannot be erased or overwritten. Such disks are called CD-ROM - Compact Disk-Read Only Memory, which means “read-only compact disk”. Later, rewritable laser discs were invented - CD-RW. On them, as on magnetic media, stored information can be erased and recorded again.

Media that the user can remove from the drive is called removable media.

Laser discs such as DVD (Digital Versatile Disk) have the greatest information capacity among removable media. They are sometimes called video discs. The amount of information stored on a DVD is measured in gigabytes. Videos recorded on DVD can be viewed on a computer, just like on a TV.

A relatively new type of external memory device is flash memory. The flash memory device is connected to the computer via a universal USB connector.

Briefly about the main thing

The computer includes internal and external memory.

The executable program is stored in internal memory (stored program principle).

Information in computer memory is in binary form.

The smallest element of a computer's internal memory is a bit. One bit of memory stores one bit of information: the value O or 1.

Eight consecutive bits form a memory byte. The bytes are numbered starting from zero. The sequence number of a byte is called its address.

In the internal memory, information is written and read by address.

A machine program is a set of instructions located in successive memory cells.

External memory: magnetic disks; optical (laser) discs - CD, DVD; flash memory.

Questions and tasks

1. Try to explain why a computer needs two types of memory: internal and external. Prepare your message.

2. What is the principle of stored program?

3. What is the discrete property of the computer’s internal memory?

4. What two meanings does the word “bit” have? How are they related?

5. What is the addressability property of the computer’s internal memory?

6. What is a machine program? What information is contained in the program command?

7. Name the computer's external memory devices and take photographs of them.

8. What types optical disks You know?

Electronic lesson supplement

Download lesson materials

Lesson Objectives: Studying new material on the topic “Principles of organizing internal and external computer memory.”

Lesson objectives:

Educational:

• introduce students to the information structure of internal and external memory;
• introduce the main topic concepts, classification and purpose of external memory devices.

Educational:

• carry out propaedeutics for the formation of intellectual and information skills;
• develop independence in thinking and learning activities.

Educational:

• cultivate interest in the subject;
• cultivate a culture of working with a computer – “user culture”;
• foster responsibility, independence, and respect for each other.

Lesson type: combined - lesson explaining new material

Forms, academic work, students: frontal work, work in pairs, individual work at the computer.

Learning Tools:

textbooks: Semakin I. G., Zalogova L. A., Rusakov S. V., Shestakova L. V. Computer Science: Basic course for grades 7 - 9. - M.: Laboratory of Basic Knowledge, 1998.
Semakin I. G., Varaksin G. S. Structured outline of the basic course. - M.: Laboratory of Basic Knowledge, 2001.

CDs: Anatomy of a Computer - 2

hardware and software:

Personal computers;
MS Windows OS application - PowerPoint program;
presentation on the lesson topic “Internal and external computer memory”;
projector.

Lesson steps:

I. Organizational part.

II. Communicate the topic and objectives of the lesson. Explanation of work on the score sheet.

III. Checking homework. Programmed control of the studied material (test).

IV. Updating basic knowledge.

V. Explanation of new material.

1. Problematic situation. “Message from the computer.”
2. information structure of internal memory.
3. information structure of external memory.
4. external memory devices.

VI. Checking students' assimilation of new material.

VII. Summing up the lesson.

PROGRESS OF THE LESSON

I. Organizational part.

The teacher greets the students, notes those who are absent in the journal, and checks the students’ readiness for the lesson.

II. Communicate the topic and objectives of the lesson.

To view the presentation with pictures, design and slides, download its file and open it in PowerPoint on your computer.
Text content of presentation slides: Purpose and device of a computer. Principles of organization of internal and external memory. MEMORY CHARACTERISTICS: Capacity – the maximum amount of information that “fits” in various devices memory; Speed ​​of accessing information; Method of accessing information - direct or sequential; Principle of writing-reading - magnetic or optical TYPES OF MEMORY ExternalInternal ROM (external storage devices) is designed for long-term storage of user information. It can be updated, and unnecessary ones can be deleted. This type of memory is not intended for storing user information. It is used by the system itself and ensures its functioning Floppy disks Hard disks Compact disks Devices based on flash memory Random access memory (RAM) Cache memory Read-only memory EXTERNAL MEMORY The main function of the computer’s external memory is the ability to long-term store a large amount of information (programs, documents, audio and video clips, etc.). d.). The device that provides recording/reading of information is called a drive or disk drive, and information is stored on media (for example, floppy disks). Information on external media has a file organization. A file is information stored on external media and has its own name.
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style.rotation FLEXIBLE MAGNETIC DISKS A floppy disk - also called a floppy disk or floppy disk - is a round flexible plate with a magnetized layer inserted into a plastic case. The flexible disk rotates in a plastic case, protected by two gaskets to reduce friction. The principle of recording on floppy disks is magnetic. Access to information is direct. In floppy disks (3.5 inches) there is a mode to protect information from erasing and writing, which is carried out by switching the corresponding switch on the plastic envelope. A standard floppy disk contains 1.44 MB of information. Floppy disks need very careful storage. They should not be wet, beaten, or handled carelessly. HARD MAGNETIC DISKSHard disk (HDD - Hard Disk Drive) refers to non-removable magnetic disk drives. Hard magnetic disks are several dozen disks placed on one axis, enclosed in a metal case and rotating at high angular speed. Speed ​​of writing and reading information from hard drives quite large (about 133 MB/s) due to the fast rotation of the disks (7200 rpm). hard drives Quite fragile and miniature elements are used. To preserve information and the performance of hard drives, it is necessary to protect them from shocks and sudden changes in spatial orientation during operation. LASER DISK DRIVES AND DISKSLaser disk drives use the optical principle of reading information. On laser discs CD (CD - Compact Disk, CD) and DVD (DVD - Digital Video Disk, digital video disk) information is recorded on one spiral-shaped track (like on a gramophone record), containing alternating sections with different reflectivity. A laser beam falls on the surface of a rotating disk, and the intensity of the reflected beam depends on the reflectivity of the track section and acquires values ​​0 or 1. DEVICES BASED ON FLASH MEMORY Flash memory is a non-volatile type of memory that allows you to record and store data in microcircuits. Devices based on flash memory do not have moving parts, which ensures high data security when used in mobile devices. Flash memory is a chip housed in a miniature package. To write or read information, drives are connected to a computer via a USB port. The information capacity of memory cards reaches 16 GB. Memory cards INTERNAL MEMORY The devices that make up the internal memory are located on the “motherboard” in system unit. This type of memory is not intended to store user information. It is used by a computer system. Properties of internal memory: Discreteness; Discrete objects consist of individual particles. Memory consists of individual cells - bits. Addressability. Entering information into memory, as well as retrieving it from memory, is carried out at addresses. RAM Memory (RAM, English RAM, Random Access Memory - random access memory) is a fast storage device of not very large capacity, directly connected to the processor and designed for writing, reading and storing executable programs and data processed by these programs. CACHE MEMORY Cache memory (from the English cache - hiding place) or ultra-random access memory is a very fast small-volume memory that is used when exchanging data between the microprocessor and RAM to compensate for the difference in the speed of information processing by the processor and the somewhat slower RAM. PERMANENT MEMORYRemote memory - BIOS (Basic Input-Output System). The data was entered into it when the computer was manufactured. Designated ROM - Read Only Memory. Stores: programs for checking equipment when loading the operating system; programs to start loading the operating system; programs for performing basic functions for servicing computer devices; computer configuration program - Setup. Allows you to set the characteristics: types of video controller, hard drives and floppy drives, modes of working with RAM, password request at boot, etc.; What is the purpose of devices for storing information in a computer? What is the essence of reading and writing information in a computer? What are CD, CD-ROM, CD-R, DVD-RW? How many times is the information capacity of a DVD larger than a CD? HOMEWORK

Attached files

Bits Bytes Information structure of internal memory - bit-byte

Properties of internal memory 1. Discreteness (lat. discretus) - intermittent, consisting of separate parts) A memory cell that stores one binary character is called a BIT. BIT 0 or 1 Binary encoding 2. Addressability Memory byte is the smallest addressable part of internal memory The processor accesses internal memory by addresses Structure of internal memory BytesBits The serial number of a byte is called its ADDRESS

File – named space on a disk for storing information Information on external media has a file organization Information structure of external memory Information structure of external memory – file Types of information: text, numeric, graphic, sound

Magnetic tape drives NMD (streamers) Cassette drives Magnetic disk drives NMD (disk drives) Compact disk drives Optical (laser) drives Floppy disk drives (floppy disks) Hard disk drives (hard drives) CD-R, CD-RW DVD drives -ROM

A device for writing and reading information from floppy magnetic disks is a disk drive (FDD - Floppy Disk Drive). The information capacity of the floppy disk is small and is only 1.44 MB. The speed of writing and reading information is also low (about 50 KB/s) due to the slow rotation of the disk (360 rpm). Floppy magnetic disks (floppy disk, floppy disk)

In order for information to be stored on a disk, the disk must be formatted, i.e. The physical and logical structure of the disk must be created. During the formatting process, concentric tracks are formed on the disk, which, in turn, are divided into sectors; for this, the magnetic head of the drive places track and sector marks in certain places on the disk.

After formatting a 3.5" floppy disk, its parameters will be as follows:

First hard drive was developed by IBM in 1973 and had a capacity of 16 KB. Hard magnetic disks are several disks placed on one axis, enclosed in a metal case and rotating at high angular speed. Due to the many tracks on each side and the large number of disks, the information capacity of hard drives can be tens of thousands of times greater than the information capacity of floppy disks and reach hundreds of GB. The speed of writing and reading information from hard drives is quite high (about 133 MB/s) due to the fast rotation of the disks (7200 rpm).

Magnetic tapes A device for writing and reading information from flexible magnetic tapes is called a streamer. Magnetic tapes are: Cassette, Reel, designed for creating data archives, backup; is a flexible plastic tape coated with a thin magnetic layer; information is recorded via magnetic recording; The capacity of magnetic tape can reach several gigabytes.

Used to store a large amount of information in a small area; the disc is made of polycarbonate, which is coated on one side with a reflective layer; information is recorded through optical recording; optical disk capacity - from 640 MB and above Laser (optical) disks

MAGNETO-OPTICAL DISK is used in the construction of optical libraries; is a polycarbonate substrate 1.2 mm thick, on which several thin-film layers are applied; information is recorded both through magnetic and optical recording; Magneto-optical optical disk capacity up to 9.1 GB.

Flash disks (cards) Flash memory is a non-volatile type of memory that allows you to record and store data in microcircuits. Devices based on flash memory do not have moving parts, which ensures high data security when used in mobile devices. Flash memory is a chip housed in a miniature package. To write or read information, drives are connected to a computer via a USB port. Information capacity of memory cards from 256 MB – 4 GB. Reading devices – Card reader.

The first samples of flash memory were developed by Toshiba back in 1984, but its mass use began only a few years ago with the advent of digital cameras. Flash memory is increasingly used for storing and transferring data. Today, manufacturers produce several types of cards and USB drives that first appeared in 2001.