Fundamentals of data storage in computers. Storing data in computer memory. The main purpose of peripheral devices

Storing data in computer memory.

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Distinguish between information storage devices implemented in the form of 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, which are electronic circuits, are characterized by 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 of its recording and reading 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 (up or down). One of the states is used to represent 0, the other to represent 1.

Trigger- This is a circuit that has a value of 0 or 1 at the output, and this value remains unchanged until a momentary impulse from another circuit causes ᴇᴦο 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.

The modern way to store bits in a similar way is 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: a positive pole to one plate, a negative pole to the other, the charges from the source will transfer to the plates. Now, if you remove the voltage source, then the charges will remain on the plates. If you connect the plates, then an electric current will arise, and the charges will be neutralized. Thus, a capacitor can be in one of two states (charged and discharged), one of which should be taken as 0, the other as 1. Modern technologies make it possible to create millions of tiny capacitors combined into one circuit on a single plate (microcircuit, chip ). This is why a capacitor has become a common way to store bits in machines.

Flip-flops and capacitors are examples of storage systems with varying degrees of resilience. The trigger loses the entered data after the power is turned off. Capacitor charges are so weak that they tend to dissipate on their own, even when the machine is turned on. It follows that, the charge of the capacitor must be constantly replenished using the so-called regeneration circuit. Because of this instability, computer memory built in this way is often referred to as dynamic memory.

Storing data in computer memory. - concept and types. Classification and features of the category "Data storage in computer memory." 2017-2018.

Computer memory consists of binary storage elements - bits (Eng. Binary Digit - a binary digit). Conventional computers use cells consisting of four consecutive bytes (words), but early computers use one- or two-byte cells (half-words), and some supercomputers use eight-byte cells.

Only one number or one command can be written to each memory cell. The binary code is stored in the cell until a new binary code is written to it or until the machine is de-energized. The division of memory into words for four-byte computers is shown in fig. 2.16.

64-bit processor

32-bit processor

16-bit

CPU

Half-word

double word

Rice. 2.16. Splitting memory into words in a PC

In modern computers, 32-bit addressing is adopted, which means that there can be 2 32 independent addresses in total. Thus, direct addressing to a memory field of size 2 32 = 4 294 967 296 bytes (4.3 GB) is possible.

External memory is located on magnetic or optical disks. Writing and reading information when working with external memory is slower than when working with NAM, but external memory is large and its contents do not change when the computer is turned off.

Non-volatile memory is represented by a memory chip, which contains information about the type of computer hardware.

Electronic circuits Data storage devices

Operational Magnetic Magnetic

storage device (RAM, RAM) or random access memory

Read Only Memory (ROM, ROM)

tape discs

Flexible Rigid

magnetic magnetic discs discs

(floppies) (hard drives)

Optical magneto-optical discs discs

Simple Recordable (CD)

Rice. 2.17. Classification of drives and devices

information storage

tera and its settings. The PC setting can be changed at the request of the user, so non-volatile memory allows not only reading data from it, but also writing it. In essence, it uses a conventional RAM chip, but made using a special CMOS technology that provides low power consumption during operation of this device, which is why non-volatile memory is often called CMOS memory. All microcircuits for portable PCs are manufactured using CMOS technology to ensure long-term operation of their batteries. The non-volatile memory chip is connected to a battery, which saves the data recorded in the chip when the PC is turned off from the network.

Devices, which are electronic circuits, have a short data access time, but do not allow storing large amounts of information. Information storage devices, on the contrary, make it possible to store large amounts of information, but the time it takes to write and read it is long, therefore, effective work on a computer is possible only when information storage devices and storage devices implemented in the form of electronic circuits are used together.

Chip (chip) BIOS (Basic Input / Output System - basic input-output system). This is software built into the computer that is available without accessing the disk; a set of programs designed to automatically test devices after turning on the power of the computer and loading the operating system into RAM.

The role of the BIOS is twofold: on the one hand, it is an integral element of the hardware (Hardware), and on the other hand, an important module of any operating system (Software). The BIOS contains the code needed to control the keyboard, video card, drives, ports, and other devices.

Typically, the BIOS resides on a ROM chip located on the computer's motherboard (which is why this chip is often referred to as the ROM BIOS). This technology allows the BIOS to always be available despite damage to, for example, the disk system and allows the computer to boot on its own. Since access to RAM (random access memory) is much faster than access to ROM, computer manufacturers design systems so that when the computer is turned on, the BIOS is copied from ROM to RAM.

Non-volatile memory is designed to store unchanging information that is written to the permanent memory chip by the computer manufacturer. The BIOS includes a program for self-testing the computer when it is turned on, drivers for some devices (monitor, disk drives, etc.), as well as a program for loading the operating system from disk devices. Currently, almost all motherboards are equipped with a chip for permanent storage of the initial executable boot code of the computer FLASH BIOS, which can be overwritten in the ROM chip at any time using a special program.

External storage device (VSD). This device is divided into random access memory, read only memory and cache memory.

External memory is designed for long-term storage of programs and data, and the integrity of its contents does not depend on whether the computer is turned on or off. Additional external memory devices are:

FDD (Floppy Disk Drive) - floppy disk drive, capacity - 1.44 MB;
CD-ROM and R/W - laser CD drive, capacity - 800 MB;
DVD-ROM and R/W - laser DVD drive, capacity - up to 16 GB;
HDD (Hard Disk Drive) - hard disk drive, capacity - more than 100 GB;
FLASH - a storage device based on memory chips, capacity - up to 8 GB.

The computer memory must consist of a number of numbered cells, each of which may contain either processed data or program instructions. All memory cells must be equally accessible to other computer devices.

RAM(RAM, eng. Random Access Memory, RAM) - designed for writing, reading and temporary storage of programs (system and application), initial data, intermediate and final results.

When the computer is turned off, the information in RAM is erased. In modern computers, the amount of memory is usually between 128 MB and 2 GB. The amount of memory is an important characteristic of a computer, it affects the speed of the computer and the performance of programs. Modern application programs often require more than 4 MB of memory to execute, otherwise the program simply will not be able to work. A portion of RAM called "video memory" contains data corresponding to the current image on the screen.

Structurally, the elements of RAM are made in the form of DIP (Dual In-line Package) microcircuits or in the form of SIP (Single In-line Package) memory modules.

A personal computer contains four types of RAM: SIMM modules used in obsolete computers on 386, 486 and Pentium processors; more advanced DIMMs used in computers from Pentium II and Celeron to Pentium III and Athlon; more modern DDR DIMMs and MMMs that are used with newer processors and motherboards. Random access memory is built on memory chips with random access to any cell. RAM is either static (on triggers) and is called SRAM (Static RAM), or dynamic (based on capacitor cells) - DRAM (Dynamic RAM).

In static RAM, a static trigger is used as an EP, which is able to maintain a state of 0 or 1 indefinitely (when the PC is turned on). Dynamic RAM is based on capacitors implemented inside a silicon crystal. Dynamic EPs (capacitors) self-discharge over time and the recorded information is lost, therefore, dynamic EPs require periodic charge recovery - regeneration. During regeneration, the recording of new information should be disabled.

Compared to static RAM, dynamic RAM has a higher specific capacity and lower cost, but more power consumption and slower performance. Random access memory devices have a modular structure. The RAM capacity is increased by installing additional modules. Access time to DRAM modules is 60-70 ns.

Modern computers have RAM, which is 512-1024 MB. The computer's processor can only work with data that is in RAM. Data from the disk for processing is read into RAM. The main memory manufacturers are IBM, Seagate, Maxtor, Western, Digital, Fujitsi and Kingston. The share of DIMM memory sales is significantly reduced, giving way to DDR DIMM (256 and 512 MB) or RIMM (128 and 256 MB) memory modules.

Read Only Memory(ROM, eng. Real Only Memory - ROM - read-only memory) - non-volatile memory used to store data that never needs to be changed.

ROM modules and cassettes have a capacity usually not exceeding a few hundred kilobytes. Structurally, the main memory consists of millions of individual memory cells with a capacity of 1 byte each. The total capacity of the main memory of modern PCs usually ranges from 1 to 32 MB.

Reprogrammable Read Only Memory(FLASH Memory) - non-volatile memory that allows multiple rewriting of its contents from a floppy disk.

Register Cache - high-speed memory, which is a buffer between the RAM and the microprocessor, allowing you to increase the speed of operations. It is advisable to create it in a personal computer with a master oscillator clock frequency of 40 MHz or more. Cache registers are inaccessible to the user, hence the name cache. According to the principle of recording results, two types of cache memory are distinguished:

Write-back - the results of operations before writing them to RAM are fixed in the cache memory, and then con-

the cache memory troller independently overwrites this data in RAM;

With write-through - the results of operations are simultaneously written to both the cache memory and the RAM.

To speed up operations with the main memory, a registered cache is used inside the microprocessor (L1 cache) or outside the microprocessor on the motherboard (L2 cache). To speed up operations with disk memory, a cache memory is organized on electronic memory cells.

Pentium and Pentium Pro microprocessors have cache memory separately for data and separately for commands, and if Pentium has a small capacity of this memory - 8 KB each, then Pentium Pro has 256-512 KB. It should be borne in mind that for all MPs, additional cache memory located on the motherboard outside the MP can be used, the capacity of which can reach several megabytes.

The main purpose of using cache memory is to compensate for the difference in the speed of information processing by the processor (its registers are the fastest) and somewhat slower RAM. The cache memory is not available to the user, it is used by the computer automatically. Keep in mind that having a 256 KB cache memory increases PC performance by about 20%.

main memory The computer is divided into two logical areas: directly addressable memory, which occupies the first 1024 KB of cells with addresses from 0 to 1024 KB - 1, and extended memory, access to the cells of which is possible using special driver programs.

Standard memory(Conventional Memory Area - СМА) is called directly addressable memory in the range from 0 to 640 KB. Directly addressable memory in the address range from 640 to 1024 KB is called upper memory(UMA - Upper Memory Area). Upper memory is reserved for monitor memory (video memory) and read-only memory. However, there are usually free areas left in it - "windows" that can be used using the memory manager as general-purpose RAM.

Extended memory - memory with addresses of 1024 KB and above. Direct access to this memory is possible only in the protected mode of the microprocessor. In real mode, there are two ways to access this memory, but only when using drivers: according to the XMS (extended Memory Specification) and EMS (Expanded Memory Specification) specifications.

Access to extended memory according to the XMS specification is organized using XMM (extended Memory Manager) drivers. This memory is often referred to as add-on memory, given that early PCs had this memory on separate add-on boards. The EMS specification is an older one, access is implemented by mapping Expanded Memory fields to a specific area of high memory. At the same time, not processed information is stored, but only addresses that provide access to this information. Memory organized according to the EMS specification is called displayed.

Extended memory can be used mainly for storing data and some OS programs. Extended memory is often used to organize virtual (electronic) disks.

video memory(VRAM) is a type of random access RAM that stores encoded images. This memory is organized in such a way that its contents are available to two devices at once - the processor and the monitor, so the image on the screen changes simultaneously with the update of the video data in the memory.

Controllers and adapters are sets of electronic circuits that are supplied with computer devices in order to make their interfaces compatible. Controllers, in addition, directly control peripheral devices at the request of the microprocessor.

Device ports are electronic circuits containing one or more I / O registers and allowing you to connect computer peripherals to external buses of the microprocessor.

The system (motherboard) board of a computer. Motherboard - the main PC board (Fig. 2.18), which houses:

processor (a microcircuit that performs most of the computational operations);
microprocessor set (chipset) - a set of microcircuits that control the operation of the internal devices of a computer;
three buses (sets of conductors through which signals are exchanged between the internal devices of a computer);
random access memory (RAM) - a set of chips designed for temporary data storage;
ROM - a microcircuit designed for long-term storage of data;
connectors (slots) for connecting additional devices;
means of monitoring the state of the system board.

External connector zones Card slots

built-in expansion peripherals

Rice. 2.18. Computer motherboard

Synchronization and overclocking of the motherboard. The motherboard's main clock generates a highly stable clock reference used to clock the processor, memory, and I/O buses. Since the speed of these subsystems varies significantly, each of them can be synchronized with its own frequency. In asynchronous type chipsets, the frequencies are relatively independent, which opens up the possibility of optimizing performance and overclocking. The most common object for overclocking is the central processor. It is quite obvious that the performance of a particular processor depends on the clock frequency of the core and the frequency of the system bus. The first component determines the rate of processing, and the second - the speed of delivery of instructions and data. The maximum allowed clock speed is determined by the delays between different signals and the power dissipation of the processor.

Cache - memory of small capacity, but extremely high speed (the time of access to the MPP, i.e. the time required to search, write or read information from this memory, is measured in nanoseconds). It is designed for short-term storage, recording and output of information in the next cycles of the machine directly involved in the calculations.

CPU. This is the central part of any modern computer that controls the rest of the devices. It contains an arithmetic logic unit, a control unit and registers for temporary storage of information. The processor reads data from the RAM (RAM) of the computer, where it sends the result of the action on this data. The processor can perform the following operations on binary numbers: arithmetic, logical, comparison operations, memory operations, and control transfer operations.

The processor performs all actions only according to the program, that is, a certain sequence of commands. Most computer errors during operation are due precisely to the mistakes of the programmer, who was unable to foresee all possible situations.

The processor performs the following functions:

data processing according to a given program by performing arithmetic and logical operations;
software control of the operation of computer devices.

The speed of a processor is determined by its clock speed. The larger it is, the faster the processor. Modern processors operate at frequencies above 3 GHz (Table 2.3).

Each specific processor can only work with a certain amount of RAM. The maximum amount of memory that the processor can serve is called

Table 2.3. Processor manufacturers

vaetsya processor address space and is an important characteristic of a computer. The address space is determined by the bit width of the address bus.

Computer Engineering- a set of devices designed for automatic or automated processing of data into information.

Computing system is a specific set of interconnected devices. The central device of most computing systems is an electronic computer (computer) or computer.

A computer is a device consisting of electronic and electromechanical components that performs data input, storage and processing operations according to a specific program in order to obtain information, the output of which is carried out in a form suitable for human perception.

Computer architecture. Under the architecture of a computer, one must understand the set of characteristics that the user needs. These are, first of all, the main devices and computer blocks, as well as the structure of connections between them and program control.

General principles for building computers that relate to architecture:

computer memory structure;
ways to access memory and external devices";
the ability to change the configuration;
command system;
data formats;
interface organization.

Based on this, it can be determined that Architecture- these are the most general principles of building a computer that implement program control of the operation and interaction of its main functional units.

The classical principles of building a computer architecture were proposed in the work of J. von Neumann. G. Goldsteig and A. Burks in 1946 and are known as "von Neumann's principles". These principles declare the following provisions of the architecture:

Using a binary data representation system. The advantages of the binary system for technical implementation gave the convenience and ease of performing arithmetic and logical operations. Computers began to process non-numeric types of information - textual, graphic, sound and others. Binary encoding of data is still the information basis of any modern computer.
Stored Program Principle. Neumann was the first to guess that a program could also be stored in the form of zeros and ones, and in the same memory as the numbers it processed. The absence of a fundamental difference between the program and data made it possible for the computer itself to form a program for itself in accordance with the results of calculations. Von Neumann not only put forward the fundamental principles of the logical device of the computer, but also proposed its structure, which was reproduced during the first two generations of the computer.
The principle of sequential execution of operations. Structurally, memory consists of numbered cells. Any cell is available to the processor at any time. Hence follows the possibility to give names to memory areas like this. so that the values stored in them can be subsequently accessed or changed during program execution using the assigned names.
The principle of random access to RAM cells. Programs and data are stored in the same memory. Therefore, the computer does not distinguish what is stored in a given memory cell - a number, text or command. You can perform the same actions on commands as on data.

Fig 3. Control device (CU). Arithmetic logic unit (ALU). Memory (memory) stores information (data) and programs, includes random access memory (RAM) and external storage devices (VSD).

Modern computer architecture. The real structure of a computer is much more complicated than the scheme discussed above (Fig. 3). In modern computers, in particular microcomputers (personal), more and more often there is a departure from the traditional von Neumann architecture, due to the desire of developers and users to improve the quality and performance of computers (Fig. 4).

The quality of computers is characterized by many indicators. This is a set of commands that a computer is able to understand and execute, the speed (performance) of the central processor, the number of peripheral devices connected to the computer at the same time, and much more. At the same time, the main indicator characterizing a computer (computer) is its speed.

Performance is the number of operations that the processor can perform per unit of time. In practice, the user is more interested computer performance- an indicator of its effective speed, that is, the ability not only to function quickly, but to quickly solve specific tasks.

As a result, all these and other factors contribute to the fundamental and constructive improvement of the element base of computers, that is, the creation of new, faster, more reliable and easy-to-use processors, storage devices, input-output devices, etc. Nevertheless, it should be taken into account that the speed of the elements cannot be increased indefinitely (there are modern technological limitations and limitations due to physical laws). Therefore, computer technology developers are looking for solutions to this problem by improving the computer architecture.

This is how computers with a multiprocessor (or multiprocessor) architecture appeared, in which several processors work simultaneously, which means that the performance of such a computer is equal to the sum of the performance of the processors.

In powerful computers designed for complex engineering calculations and computer-aided design (CAD) systems, two or four processors are often installed. In super-powerful computers (such machines can, for example, simulate nuclear reactions in real time, predict weather on a global scale, simulate full-scale scenes for cinema and animation), the number of processors reaches several tens.

Rice. 4. General structure of a modern microcomputer

All major architectural blocks consist of separate smaller devices that perform well-defined functions.

In particular, the central processing unit includes an arithmetic logic unit ( ALU). internal storage device in the form of processor registers and internal cache memory, control device ( uu).

The input device, as a rule, is also not one structural unit. Since the types of input information are diverse, there can be several sources of input data. The same applies to output devices.

CPU is the central computing unit in any type of computer. It performs calculations on the program stored in RAM and provides general control of the computer.

The processor contains at least:

Arithmetic logic unit (ALU), designed to perform arithmetic and logical operations;

Control device (CU), designed to perform general control of the computing process according to the program and coordination of all computer devices. The control unit in a certain sequence selects a command after a command from the RAM. Then: each command is decoded, as needed, data elements from the RAM cells specified in the command are transferred to the ALU. The ALU is configured to perform the action specified by the current command (I/O devices may also take part in this action); command is given to perform this action. This process will continue until then. until one of the following situations occurs: the input data has been exhausted, a command has been received from one of the devices to stop working, the computer's power has been turned off.

storage device (storage)- this is an architectural unit of a computer designed for temporary (RAM) and long-term (permanent memory) storage of programs, input and output data, as well as intermediate results on external storage devices (VZU).

Random Access Memory (RAM)- serves for receiving, storing and issuing information. It contains programs and data available for use by the microprocessor, as well as intermediate and final results of calculations. The process of program execution is reduced to converting the initial state of memory into the final (final) one. RAM is a volatile device, which means that information is lost when the power is turned off. The speed of the computer depends significantly on the speed of the RAM. Therefore, elements for RAM are constantly being searched for, spending less time on read-write operations. The problem is solved by building a multi-level memory.

RAM consists of two or three parts: the main part of the larger capacity is built on relatively slow (cheaper) elements, and the additional (so-called cache memory) consists of high-speed elements. The data most frequently accessed by the processor resides in cache memory, while most of the operational information is stored in main memory.

Read Only Memory (ROM). A non-volatile device designed for long-term storage of service and primary information. Presented in the form of microcircuits located on the motherboard (system) board.

Externalstorage device (VZU). Non-volatile devices that provide reliable storage and issuance of information. They store frequently used programs and data (see storage devices). However, the speed of data exchange between permanent memory and the central processor, in the vast majority of cases, is much less than that of RAM.

Input devices (IUV) and output (UV), belong to the category of peripheral devices. Previously, the operation of I / O devices was controlled by the central processor, which took a lot of time. The architecture of modern computers provides for the presence of channels for direct access to RAM for data exchange with I / O devices without the participation of the central processor, as well as the transfer of most of the control functions of peripheral devices to specialized processors, unloading the central processor and increasing its performance.

Interrupt system. interruption A situation is called a situation that requires some action by the microprocessor when a certain event occurs. An interrupt system is understood as a software and hardware complex that provides the execution and processing of interrupts.

The processor must respond quickly to various events occurring in the computer as a result of the actions of the operator or without his knowledge. Examples of this kind include keystrokes on the keyboard, an attempt to divide by zero (during program execution), a power failure (other hardware failures), scheduled calls to the operating system kernel, and more. The necessary response to interrupts is provided by the interrupt system.

Interrupt handling is reduced to suspending the execution of the current sequence of commands, instead of which another sequence corresponding to this type of interrupt and called the interrupt handler begins to be interpreted. After its implementation, the execution of the program can be continued if it is possible or appropriate, depending on the type of interrupt.

I/O port system provides a direct connection of a peripheral device adapter to the system bus, that is, in fact, is the point of such a connection of a peripheral device to a computer system. Each I/O port has its own address, and multiple I/O ports can be assigned to a peripheral device. A set of input-output ports form a system of input-output ports. Simplified, the I / O port can be considered a register into which information is written to transfer it to a peripheral device or from which information received from a peripheral device is read.

From the user's point of view, port- this is an interface (connector) for connecting a device (keyboard, mouse, display, printer, headphones, etc.) to a computer. Typically, input-output ports are located on the rear panel of the system module case, some of them can also be placed on the front panel.

Adapter, controller. The concept of "peripheral device adapter" can be considered a synonym for the term "controller", but the latter is more often used for devices that implement more complex functions for controlling peripheral devices (Fig. 5).

Rice. 5.Video controller. Controls the display of the image

Advanced peripheral controllers include specialized microprocessors and memory. The same applies to peripheral devices with complex operation algorithms that require sophisticated control units. From the user's point of view, (adapter or controller) is a board with a set of chips and I / O ports, its task is to control the device connected to it. It can be a display, a printer, audio devices, etc.

interface adapter- this is a means of interfacing the central part of the computer with peripheral devices in which all physical and logical parameters correspond to predetermined parameters (a certain protocol) and are widely used in other devices.

Rice. 6. Interface adapter

Modern computer system architecture. Having retained the principles of building a computer architecture according to Neumann, modern architecture has been enriched with additional principles, and today computer architecture is determined by the following principles:

Principle of program control. Provides automation of the process of computing on a computer. According to this principle, for solving each problem, a program is compiled that determines the sequence of computer actions. The efficiency of program control will be higher when the problem is solved by the same program many times (albeit with different initial data).
The principle of a program stored in memory. According to this principle, program commands are given, like data, in the form of numbers and are processed in the same way as numbers, and the program itself is loaded into RAM before execution, which speeds up the process of its execution.
Random access principle to memory. In accordance with this principle, elements of programs and data can be written to an arbitrary location in RAM, which allows you to access any given address (to a specific memory location) without looking at the previous ones.
The principle of separation of functions. The processor controls all operations at the highest level, while a specific interpretation of its general commands for individual devices is implemented by special control devices - controllers. The processor can process information only if it has already undergone primary processing. This function is taken over by the input device controllers. They bring the input data to a single standard. Then the data is sent to the RAM, where they are arranged into cells and provided with links (addresses) necessary for their use. The output of information also occurs through the mediation of output control devices, which again produce reformatted data in the desired standard. In principle, all computer devices have their own controllers (drives, monitor, printer, plotter, streamer, etc.). Based on this, one of the important principles of computer operation can be formulated.

Functional subsystems. In the course of its work, the computer performs:

Entering information from outside;
Temporary storage;
conversion;
Conclusion in a form accessible to perception by her person.

The process of obtaining data by a computer is called briefly " input”, and issuing it to the user - "conclusion". These processes are so important that a large number of various devices have been proposed for their implementation. In addition, we must not forget that "input" and "output" are two sides of one process of information exchange, and without one of them there is no other. Therefore, when they talk not about data transformation, but about their transfer to a computer for calculations and obtaining the final results, the term “input-output” is used.

During the input process, data is converted to a format that can be perceived by a computer, and during the output, to a form familiar to humans.

In each of the listed stages of the process, a separate functional subsystem is implemented:

data entry subsystem;
data storage subsystem;
data conversion subsystem;
information output subsystem.

All subsystems are interconnected by exchange channels grouped into flows. In addition to data and commands, they carry timer signals and supply voltage to all computer blocks. These streams have a constructive expression in the form of wires and connectors, which have the name of the bus (see below).

Input device subsystem. The input of information into a computer is carried out by specialized devices, both standard (see below) and non-standard (optional).

Entering information into a personal computer is carried out in three stages:

perception of information from outside;
bringing data to a specific format understandable by a computer;
data transfer to a computer bus;

Output device subsystem. The information output subsystem allows the computer user to obtain the results of work in the form familiar to him. output devices as well. like input devices, they can be standard (see below) and non-standard (optional).

The output of information is also carried out in three stages, and their order is the reverse of that in the input process:

perception of information transmitted over the bus channels;
bringing information to the format characteristic of the output device;
issuing the results of the work. output devices.

Conversion Subsystem. The transformation of data into information in a computer is carried out by the processor. The processor, at a minimum, contains a control device ( uu) and arithmetic logic unit ( ALU). The control device is essentially the "master" of the computer and performs the following functions:

sets the order for tasks performed by the system;
generates control signals for the distribution of operations and data flows both inside the arithmetic logic unit and outside it;
manages the transfer of information on the address bus and data bus;
receives and processes service signals following the system control bus.

Storage subsystem. In order to work effectively with data, the processor needs to have fast and free access to them. The functions of intermediate storage are performed by the information storage subsystem. Having entered the computer from the input subsystem, the information reduced to a certain internal standard is located in the cells of the RAM, after which, as necessary. processed by the processor.

The memory of a personal computer is implemented on electronic elements and, as mentioned above, is volatile. This way of storing information is very vulnerable. At the end of the session, the contents of RAM are written to disk. Now a sudden power outage is not dangerous for the data, because the information recorded on the disk will restore everything in memory. what was before.

Many more reliable devices have been created for long-term and reliable data storage; magnetic and magneto-optical drives, magnetic tape drives and others.

For external storage devices ( VZU) has two main advantages over RAM:

storage of information does not require energy supply;
the amount of information can be extremely large.

Based on these principles, it can be argued that modern computer- this is a technical device that, after entering into the memory of the initial data in the form of digital codes and a program for their processing, also expressed in digital codes, is able to automatically carry out the computational process specified by the program and issue ready-made results of solving the problem in a form suitable for human perception.

Methods computer classifications. The range of types of computers today is huge: machines differ in purpose, power, size, element base, etc. Therefore, computers are classified according to different criteria. It should be noted that any classification is to some extent conditional, since the development of computer science and technology is so rapid that. for example, today's microcomputer is not inferior in power to five-year-old minicomputers and even supercomputers of the recent past. In addition, the assignment of computers to a certain class is rather conditional due to the vagueness of the division of groups, and due to the introduction of custom assembly of computers into practice, where the nomenclature of nodes and specific models are adapted to the requirements of the customer. Consider common criteria for classifying computers.

Classification by purpose

large electronic computers (BEVM);
minicomputer;
microcomputer:
personal computers.

Mainframes(Mainframe) . They are used to serve large areas of the national economy. They are characterized by powerful parallel processors (the number of which reaches up to 100), integral performance up to tens of billions of operations per second, and a multi-user mode of operation.

A computer center is created on the basis of large computers, which contains several departments or groups (Table 1). The structure of a computer center based on a mainframe computer can be as follows:

CPU- the main unit of the computer. in which the data is processed and the results are calculated. It consists of several system units in a separate room, where a constant temperature and humidity are maintained.
System Programming Group- is engaged in the development, debugging and implementation of software necessary for the functioning of the computer system. System programs provide the interaction of programs with equipment, that is, the software-hardware interface of a computer system.
Application Programming Group- is engaged in the creation of programs for performing specific actions with data, that is, providing a user interface for a computer system.
Data preparation group- is engaged in the preparation of data that will be processed on application programs created by application programmers. In particular, this is typing, scanning images, filling in databases.
Technical Support Group- is engaged in maintenance of the entire computer system, repair and debugging of equipment, connection of new devices.
Information support group- provides technical information to all divisions of the computing center, creates and saves archives of developed programs (program libraries) and accumulated data (data banks).
Department of data issuance- receives data from the central processor and converts them into a form convenient for the customer (printout).

Large computers have a high cost of equipment and maintenance, so the work is organized in a continuous cycle.

Minicomputer. This category is similar to mainframe computers, but smaller. Used in large enterprises, scientific institutions and organizations. Often used to control industrial processes. They are characterized by multiprocessor architecture, connection of up to 200 terminals, disk storage devices that grow up to hundreds of gigabytes, branched peripherals. To organize work with minicomputers, a computer center is needed, but smaller than for large computers.

Microcomputer. Microcomputer (microcomputer) - a computing system in which a microprocessor is used as a control and arithmetic device. In more advanced microcomputers, several microprocessors can be used. The performance of this system is determined not only by the characteristics of the processor used, but also by the capacity of the available RAM, types of peripheral devices, the quality of design solutions, expandability, etc. Now they have become tools for solving complex problems. Microprocessors have become more powerful and peripherals more efficient, so microcomputers are now replacing minicomputers and the difference between them is gradually decreasing. This course of study is designed for computers of this category.

Microcomputers can be conditionally divided into professional and household. Due to cheaper hardware, the line between them is gradually blurred. Since 1999, an international certification standard has been introduced - specification RS99:

mass personal computer (Consumer PC) - relatively inexpensive systems that meet user requirements;
business personal computer (Office PC) - have a minimum means of reproducing graphics and sound;
portable personal computer (Mobile PC) - differ in the presence of means of communication of remote access (computer communication);
workstation (Workstation) - differ in increased requirements for storage and processing devices;
entertainment personal computer (Entertainment PC) - they focus on multimedia with the help of advanced means of reproducing graphics and sound.

Classification of microcomputers by purpose or level of specialization.

multi-user microcomputers(Servers) are microcomputers operating in the time-sharing mode providing the work of several users at the same time. They run in one small rack or desktop form and in most cases are a subset of a computer network.
specialized or workstations(AWP) - are a microcomputer equipped with all the tools necessary to perform a certain type of work. Distinguish between engineering, graphic, computer-aided design, publishing (desktop publishing) and others.
embedded microcomputers- are computing systems designed to solve specific problems. Used to control (for example, a machine tool or a set of machine tools, scientific equipment, a combat unit, etc.) and process measurements. Structurally, they are implemented in the form of one or more boards and do not provide a wide range of computing functions, as well as standard user interaction.

Size classification. In addition to the intended purpose, depending on the design use, microcomputers are divided into stationary and portable.

Stationary microcomputers. Mounted on a table, cabinet or in the form of a small rack on the floor.
Portable microcomputers. They have a relatively small mass and dimensions, are transported by one person, as a rule, do not have autonomous power supply;
Portable self-powered microcomputers. They fall into a number of categories:
Knee-highs(Laptop), made in the form of a diplomat;
Pocket(Pocket) that fit in your pocket.

The most common are desktop microcomputers that allow for easy reconfiguration. Portable are convenient for use, have means of computer communication. Pocket models can be called "intelligent" notebooks, they allow you to store operational data and get quick access to them.

Compatibility classification. There are a great many types of computers that are assembled from parts made by different manufacturers. It is important to ensure the compatibility of the computer, which has several levels:

hardware compatibility (platform IBM PC and Apple Macintosh);
compatibility at the operating system level;
software compatibility;
data level compatibility.

Questions for self-control

What is called computing?
1. What is a computer system?
2. What is a computer?
3. What is computer architecture?
4. List the principles of building a computer architecture according to Neumann?
5. What is speed?
6. What is computer performance?
7. What is a processor?
8. What is an Arithmetic Logic Unit?
9. What is a control device?
10. What is a storage device?
11. What is working memory?
12. What is an external storage device?
13. What is an interrupt?
14. What is an interrupt system?
15. What is interrupt handling and interrupt handler?
16. What is an I/O port?
17. What is an adapter and controller?
18. What is an interface adapter?
19. What functions does the computer perform during its operation?
20. List the functional subsystems of a computer.
21. What functions does the data entry subsystem perform?
22. What functions does the data output subsystem perform?
23. What functions does the data conversion subsystem perform?
24. What is a microcomputer?
25. What is a server?
26. What is ARM?
27. List the types of compatibility of computer systems?

Even for small one-time statistical studies, the efforts expended on the timely and complete description of the arrays used, the variables included in them, and all steps of statistical analysis fully pay off. Early and thorough documentation removes many misunderstandings. Large statistical studies are carried out collectively, the composition of the participants in the work partially changes in the course of its implementation, the processing of the collected materials is stretched in time and is carried out iteratively, when the data are again and again accessed to test the hypotheses that arise during the analysis. In many studies (for example, medical ones), there is often a constant replenishment of data with new information. Under these conditions, thoughtful and careful documentation becomes simply necessary as the most important condition for ensuring continuity in the implementation of the study. Let us dwell briefly on certain aspects of this process.

Certification of research, arrays, variables, methods of analysis. For each of the above objects, it is desirable to have the following in the computer: 1) a short name that must appear in all outputs; 2) the full name, which is mainly used in reports, but sometimes also in search results, when the short name is not enough for an unambiguous understanding of their meaning; 3) a description that briefly reveals the content of the work for research and indicates the relationship between the arrays; for arrays, specifies the conditions for their collection or formation; for variables, gives a way to get, measure, or register them; for the method of analysis, references to sources where an exact description of the method can be found. Descriptions are mainly used in the formation

reports and sometimes as an auxiliary comment to facilitate the understanding of individual outputs; and only for variables 4) an indication of the limits of change or accepted values, which must be used for control when entering data, as well as when building output tables.

If in the course of the analysis separate arrays are singled out or new auxiliary variables are introduced, then they must be described in the same detail as the main arrays and variables.

The automation of research documentation described above is achieved at the current level of development of mathematical software by fairly simple means, but it allows solving very important tasks: it controls variables during input; provides "offline readability" of all issued tables; increases the likelihood of detecting inaccuracies and errors in descriptions; facilitates reporting.

In addition, it is desirable to maintain in a computer or with the help of special filing cabinets: what types of analysis (programs) and to which subarrays were applied; what was the revealed measure of the dependence between the signs, the success of the forecast, the adequacy of the display of objects in a space of lower dimension, etc.; addresses where relevant results are stored in a computer or on shelves, as well as maintaining multi-purpose text comments both on the logic and course of analysis, and on individual printouts.

10.1.2. Data entry and storage.

For input, either punched cards are usually used, or a display with a template highlighting into which coded values are entered, or a display with a list of possible values \u200b\u200bof the variable - the so-called "menu". The last two methods allow you to immediately detect gross errors during input. Using the "menu" requires more input time. "Menu" should be configured automatically according to the description of the variables. Data storage should be organized in such a way that it can be easily edited and replenished.

10.1.3. View data.

It is essential that the data collected in a statistical study be carefully reviewed and edited before the main statistical technique is applied to it. Mistakes

in the data can lead to unexpected results, sometimes interpretable, sometimes not, but always wrong.

Viewing data has the following purposes:

1) detection of gross errors in the research dictionary, as well as errors made during coding, perforation and data entry into the computer;

2) an indication of possible outliers or anomalous, i.e., observations that stand out sharply in magnitude, which may not be representative of the population under study (for more details, see § 11.5);

3) obtaining the first, rough idea about one-dimensional and, partially, two-dimensional distributions.

Let us point out some techniques that facilitate the review of data, or, as they sometimes say, screening.

A printout of the data entered into the computer in tabular form by objects, sometimes with their preliminary sorting according to the value of some attribute. At the same time, the presence of gross errors in setting the data format, the correctness and readability of the name of the study and the names of variables, the completeness of the entered material and the absence of unnecessary data, as well as whether the numerical values of the variables or their codes fall within the specified range are checked. Viewing the variables arranged in columns usually allows you to immediately highlight gross errors. If desired, the columns can also be viewed on the display screen. However, a well-formatted paper printout is a handy reference document for other issues that may arise in later stages of the analysis.

Construction of one-dimensional distributions. If the computer builds a histogram (see § 10.3), then it is convenient to fill its column with the numbers of observations. In the extreme case, if there are too many observations, then indicate separately the numbers of observations that have gone beyond -th quantiles.

It is also convenient to use the indication of observation numbers when constructing two-dimensional printouts. If several observations fall into one point, a special sign is put on the graph, and the observation numbers are printed below. Two-dimensional large-format printouts are very convenient for the formation of preliminary meaningful hypotheses about the relationship of variables. Mathematical issues of constructing empirical distributions are considered in § 10.3.

The CPU has access to the data in RAM. The work of the computer with user programs begins after the data is read from external memory into RAM.

RAM works in sync with the CPU and has a fast access time. RAM stores data only when the power is on. A power outage leads to irreversible data loss, so a user who works with large amounts of data for a long time is recommended to periodically save intermediate results on external media.

RAM

Memory functions

1) receiving information from other devices;

2) memorization of information;

3) transfer of information on request to other devices of the machine.

Peripherals

The functions of peripheral devices include the input and output of information.

Each device has a set of characteristics that allow you to choose a device configuration that is best suited for solving a certain range of tasks using a computer.

The main purpose of peripheral devices

Ensure that programs and data for processing enter the PC from the environment, as well as the output of the results of the PC in a form suitable for human perception or for transfer to another computer, or in another required form.

Peripherals can be divided into several groups according to their functional purpose:

1. I/O devices- designed to enter information into a PC, output it in the format necessary for the operator, or exchange information with other PCs. External drives, modems can be attributed to this type of PU.

2. Output devices– designed to display information in the format required by the operator. This type of peripherals includes: printer, monitor, audio system.

3. Input Devices– Input devices are devices through which information can be entered into a computer. Their main purpose is to implement the impact on the machine. These types of peripherals include: keyboard, scanner, graphic tablet, etc.

4. Additional launchers- such as the "mouse" manipulator, which only provides convenient control of the graphical interface of PC operating systems and does not carry pronounced functions input or output of information; WEB-cameras that facilitate the transmission of video and audio information on the Internet, or between other PCs. The latter, however, can be attributed to devices input, thanks to the ability to save photo, video and audio information on magnetic or magneto-optical media.

binary code

Information always has the form of a message, and the message is encoded by one or another set of characters, symbols, numbers. From a technical point of view, the most convenient and efficient is to use a binary code, that is, a set of characters, an alphabet consisting of a pair of numbers (0,1). Since binary code is used to store information in computers, it is also called machine code.

The digits 0 and 1 that form the set (0,1) are usually called binary digits because they are used as an alphabet in the so-called binary number system. The number system is a set of rules and techniques for naming and writing numbers, as well as obtaining the meaning of numbers from the symbols depicting them. The number of characters in the alphabet of a number system is usually reflected in its name: binary, ternary, octal, decimal, hexadecimal, etc. Generally speaking, number systems with any number of characters in the alphabet can be considered. Currently, the Arabic decimal number system is generally accepted, the alphabet of which consists of ten digits (0,1,2,3,4,5,6,7,8,9). However, the decimal system is too complicated for use in a computer, since for its application it is necessary to select technical methods for representing ten different digits. From the point of view of the technical implementation of a computer, it is much easier to work with just two digits of the binary system (0.1).

The elementary computer memory device, which is used to display one binary digit, is called a binary digit or bit.

The internal bit depth of the processor determines how many bits it can process simultaneously when performing arithmetic operations.

The external bit depth of the processor determines how many bits it can simultaneously receive or transmit to external devices.

Literature

1. A.V. Mogilev, N.I. Pak, E.K. Henner. Informatics. M., 2000.

2. A.Ya. Saveliev. Fundamentals of informatics. M., 2001.

3. Compas Magazine Articles 2007

4. Informatics: basic course, 2nd edition. Publishing house "Peter", 2005