Computers use a number system. Representation of information in computers. Representation of numerical information in a computer

1.3. Scope of computer

By purpose, computers can be divided into three groups: universal ( general purpose), problem-oriented and specialized.

Universal computers are designed to solve a wide variety of engineering and technical problems: economic, mathematical, informational and other problems that are distinguished by the complexity of algorithms and a large amount of processed data. They are widely used in public computing centers and other powerful computing systems.

Problem-oriented computers are used to solve a narrower range of problems associated, as a rule, with the management of technological objects; registration, accumulation and processing of relatively small amounts of data; performing calculations using relatively simple algorithms; they have limited hardware and software resources compared to mainframe computers.

Problem-oriented computers include, in particular, all kinds of control computing systems.

Specialized computers are used to solve a narrow range of problems or to implement a strictly defined group of functions. Such a narrow orientation of computers makes it possible to clearly specialize their structure, significantly reduce their complexity and cost while maintaining high performance and reliability of their operation.

Specialized computers include, for example, programmable microprocessors for special purposes; adapters and controllers that perform the logical functions of controlling individual simple technical devices harmonization and interfacing of the work of nodes of computing systems.

The use of computers is very common in almost all areas of human life.

So, for example, computers are used:

1. In industry (specialized computers)

2. In engineering (on-board computers)

3. Practically in any industrial and service sector (personal computers and laptops)

4. On the Internet (servers)

5. In everyday life.

2.practical part.

customization options for Windows XP (Windows Vista)

Operating system Microsoft Windows XP (from English eXPerience - experience) is an OS of the family Windows previous generation based on NT technology.

To run Microsoft Windows XP, you need a personal computer that meets the following minimum system requirements: processor - Pentium-compatible, clock frequency from 233 MHz and higher; the amount of RAM - 64 MB; free disk space - 1.5 GB. However, for stable and fast operation, it is recommended to install this operating system on a computer with the following optimal characteristics: processor - Pentium-II-compatible (or higher), clock frequency of 500 MHz or higher; the amount of RAM - 256 MB; free disk space - 2 GB. CD-ROM drive, modem with a speed of at least 56 Kbps.

Now, when you press the Start button, a dynamic menu appears, containing icons for only five programs that you use most often. This allows you to get started with the right applications significantly faster. Microsoft browser icons are also located here. Internet Explorer 6 and the Outlook Express 6 email client, the Log Off and Turn Off Computer buttons allow you to end the current Windows session and turn off the computer.

In the Microsoft Windows environment, the user often has to work simultaneously with several documents or a set of different programs. At the same time, inactive applications are minimized to the Taskbar, as a result of which it sooner or later overflows with icons, and switching between tasks becomes difficult. In order to unload the Taskbar and free up more workspace for displaying the icons of running applications, Windows XP uses the so-called task grouping algorithm, according to which the same type of programs running on the computer at the same time are combined into a logical visual group.

Windows XP includes a special mechanism - fast session switching (Fast User Switching), with the use of which you can quickly, without registration, connect new users and user groups to work with the operating system. There is also the ability to switch between multiple sessions without the need to save data or reboot the system. At the same time, each user can independently change Windows settings and work with their own files and documents, create, modify and save any data independently of others. Windows users xp. For each new session, the operating system allocates a special section of the upper memory in the amount of 2 MB, but this amount does not limit the number of applications that can be launched by the user. In particular, the Fast User Switching mechanism enables a user working, for example, with text editor, leave your computer for a while, and while you're away, another user can open their own Windows session and surf the web or download a game. At the same time, the text edited by the absent user is still stored in memory: returning to the computer, the user can continue working with the document from the point where it was interrupted without rebooting the system and without restarting the corresponding program.

operating room Windows system XP includes many different settings. Some of them are listed below:

Clearing the paging file before rebooting the system

Disable built-in debugger Dr. Watson

Disable Last File Access Recording (NTFS)

Disable System Files Protection (SFC)

Enable UDMA-66 support on Intel chipsets

Include Num Lock while loading

Automatically unload unused libraries

Disable Windows XP Tracking User

Run 16-bit programs in separate processes

Do not send bug reports to Microsoft

Password when waking up from Standby

Optimize system files during boot (boot defrag)

Error messages

The path to the Windows distribution and system folders for active user

Write Recovery Console to HDD

Automatic Windows Updates

Windows Prefetcher Service

Login

Show running commands on startup and logout

Automatic login without entering a password

Show message on login

Don't show last username

Use the welcome page

Use fast user switching

System acceleration

Disable unused devices in Device Manager

Disable indexing

Increasing the performance of NTFS

Speed ​​up the action file system

Disable Universal Plug and Play

Office XP - disable sending errors

Change the priority of interrupt requests (IRQ)

Windows operation with zip archives

Disable support for zip archives

System Restore

Disable System Restore

Recovery point lifetime

System failure

Automatically restart your computer

Write an event to the system log

Send administrative notification

Writing debug information

Memory Options

Do not use the swap file to store the system kernel

Large system cache

Memory allocation for I/O operations

Ways to system utilities

Use your own disk defragmenter

Use your system cleaner

Use your program for data archiving

Vista setup

Disable UAC

Consider examples of how to set up:

1. Windows Automatic Updates

Automatic control Windows update xp. Also, this option can be configured in the following way: Control Panel - System - Automatic Update.

HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update

Windows XP uses the following values:

Disable automatic updates

Notify when updates can be downloaded

Download updates, then notify when ready to install

AUOptions = 3 and other values

2. Automatic login without entering password

Allows you to automatically log in without choosing a name and entering a password. Also, automatic login can be enabled in the following way: Start - Run - type "control userpasswords2", in the window that appears, uncheck "Require username and password", after clicking OK, a window will appear where you need to specify a username and password. If auto-login is enabled, you can bypass it by holding SHIFT key when the computer boots up.

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon

STRING AutoAdminLogon, takes the value "1" - Automatic login is enabled, "0" - disabled.

STRING DefaultUserName, the username used for automatic login

STRING DefaultUserPassword, user password

STRING DefaultDomainName, the default domain used for computers on the network

Note: the password is stored in the registry in unencrypted form.

If the display of the previous name is disabled when the computer is booted (the DontDisplayLastUserName parameter), automatic login will not work!

If the option resets after a reboot, create a password for your account (Control Panel - Accounts users) or use the control userpasswords2 applet (see above).

3. Setting the time and date

Start Menu - Control Panel - Date, Time, Language and regional standards-Date, time - the desired time is set, the desired date - apply - OK.

BIBLIOGRAPHY:

1. Akulov O. A., Medvedev N. V. Informatics: basic course. Moscow: Omega-L, 2006.

2. Dorot V. A., Novikov F. N. Explanatory dictionary of modern computer vocabulary. 2nd ed. St. Petersburg: BHV, 2001.

3. Installing Windows XP [Electronic resource]: - Access mode: http://reestr.hotmail.ru/publik/instal_XP.htm

4. Informatics: Textbook. Ed. Makarova N. V. M.: Finance and statistics, 2000.

5. Lesnichaya I.G. Informatics and Information Technology. Tutorial. Moscow: Eksmo Publishing House, 2007

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Positional number systems allow you to write numbers. The elements of the PSS are symbols. For example, in the decimal number system, the symbols 0, 1, ..., 9 are used. Let B be the base of the PSS, i.e. a number equal to the number of characters. For decimal ss. In PSS, a proper decimal fraction is represented as

where and are the number of digits before and after the decimal point, respectively.

Example.

In addition to decimal, binary, octal and hexadecimal SS are used. Binary SS uses the symbols and, octal uses , and hexadecimal uses .

Example.

Representation of numerical information in a computer

To represent numbers in computers, the binary number system is used. The number itself can be represented in various formats: as a natural number, as an integer, with a fixed point, with a floating point, in binary decimal format, etc.

Data units

The units of measurement of data volume are based on the binary number system.

Data units. Numbers in computers are transmitted over wires (tires) or stored in memory cells. The wire can be either zero or high potential, and the memory cell can be in one of two stable states. An analogue of these states is a binary digit. One binary digit was assigned a new unit of data, which was called bit.

The remaining off-system units are presented in Table.

Table - Off-system units of measurement of data volume

Representation of symbolic information in a computer. ASCII (American Standard Cods for Information Interchange) is used to represent character information in computer memory. This code consists of 7 bits. It can be used to encode characters. Character encoding is carried out by natural numbers from 0 to 127. Each character has its own number. The first code values ​​from 0 to 31 are used for service characters. If these codes are used in the symbolic text of the program, then they are not displayed on the screen and are considered spaces. Then comes the punctuation Special symbols and signs of operations, numbers, etc. Capital letters of the Latin alphabet start with 65 and end with 90, and lowercase letters from 97 to 122. If 8 bits are allocated for the character code, then another 128 numbers can be used to encode, for example, the Russian alphabet.

Windows 2000 uses the Universal Coding System UNICODE characters. 16 bits are used to encode characters. In this coding system one can put various characters, which is enough to accommodate the symbols of the main languages ​​of the planet.

Representation of logical information in a computer. In Pascal, the character code is returned by the ord function. Under the boolean type is assigned 1 bit: ord (false) =0, ord(true) =1.

Variable length fields are 0 to 256 bytes in size.

Image encoding. The image on the monitor screen is formed by a system of luminous dots. It is called raster. Each point is characterized by coordinates, color and brightness. For black and white images, gradation of 256 shades of gray is generally accepted, for encoding of which 1 byte is used.

It is believed that any color can be obtained by mixing red (Red), green (Green) and blue (Blue). This method of obtaining color is called RGB. If for each color 8 bits are used to grade its intensity, then 24 bits are required to set the color of one point, allowing you to get 2 24 \u003d 16777216 different colors. This corresponds to the ability of the human eye to distinguish colors, so this way of presenting graphic information is called full color (True color).

If 16 bits are used for color encoding, then the method is called high color.

If 8 bits are used for color encoding, then the encoding method is called index. Each number (index) is assigned its own color sample, which is placed in the reference table - palette.

Audio encoding. When playing sounds, the table-wave synthesis method is used. In special tables, the main parameters of the sound of all the main instruments are collected in numerical form.

concept software(ON). Software products are conditionally divided into three classes:

• - system software;
• - application programs;
• - programming technology tools.

System software ensures efficient and reliable operation of the computer, creates an efficient operating environment for the execution of other programs, performs hardware diagnostics, copies, restores and archives files, provides an operator interface.

The most common operating systems include MS DOS, Windows 95, OS/2, NetWare, Windows NT, Unix. The system includes basic and service software. The basic software includes operating system, shell and network system. The service software expands the capabilities of the basic one and provides computer diagnostics, virus protection, file archiving, disk and network maintenance.

Operating shells are programs that facilitate communication between the user and the computer. Shells can be text and graphic. To popular text shells operating system MS DOS includes Norton Commander 5.0 (Symantec), XTree Gold 4.0, Norton Navigator, etc. The most popular are Windows graphical shells.

The programs included with the service software are called utilities, such as Norton Utilities (Symantec Corporation).

Application packages include problem-oriented, computer-aided design, general purpose, integrated packages ( Microsoft office), office, desktop publishing systems, software multimedia. Problem-oriented ones include software for automated accounting, financial activities, personnel records, inventory and production management, banking information systems, etc. General-purpose application programs include DBMS, word and spreadsheet processors, and presentation graphics tools. Office PPPs include organizers, translation programs, and e-mail.

Electronic computers are electronic devices designed to collect, transmit, store, process and issue information. Often the term "electronic computing" is identified with another - "electronic computer" (computer). In essence, in addition to computers, electronic devices can also be attributed to electronic computing devices that ensure the transmission of information (various data) over distances. These communication devices make it possible to combine several computers into a single complex or enter data into a computer from points remote from it, as well as transfer calculation results to them.

Computers are divided into digital and analog. In turn, digital computers are divided into universal and control.

Universal computers are designed to solve problems (information processing), the specific nature of which is not specified during its development. The mainframe computer consists of a set of devices of various functional purpose interconnected by wires. The specific set of devices that compose a computer of this type should be entirely determined by the nature of the tasks for which this machine is intended. In principle, all computer devices can be attributed to one of the following groups: 1) input devices designed to enter information and programs into a computer; 2) storage devices that store information; 3) an arithmetic device that processes information in accordance with a given program; 4) output devices that provide results; 5) control devices that coordinate and control the operation of both individual devices and the computer as a whole.

Computer storage devices are divided into operational and external. Operational - high-speed, relatively small capacity; it stores the data used at a given step of calculations; all other information is stored in external memory - relatively slow and large capacity. In modern computers, it is accepted (constructively and formalized) RAM and the arithmetic unit to be combined into a single block-central calculator (processor), to which, with the help of special channel devices included in the central calculator, other devices are connected, which are commonly called peripheral. A modern computer is a complex complex, the operation of which is controlled by the input of the computing process) is automated with the help of special control programs included in the mathematical software of the computer.

Control computers are designed to control processes in a variety of areas. The information entered into them is data on the course of a process received from sensors. The results of processing (calculations) are implemented through devices that ensure the required flow of the controlled process. Analog computers (AVM) are intended for solving equations, electronic simulation of various processes.

Currently, computers are widely used in medicine for the purposes of machine diagnostics, building automated systems control (ACS).

Electronic computers (computers). The main circuit elements of a computer are electronic devices - vacuum tubes or transistors (see Electronic amplifiers). Computers in comparison with other types of computers (arithmometer, keyboard electromechanical machine) are faster, more versatile and reliable in operation, and most importantly - more automated. Before starting work, a calculation program and initial data are entered into the computer to solve the problem, after which the calculations are performed automatically until the final result is obtained. In addition to the usual mathematical and logical operations according to a given program, computers can perform conditional transition operations that change the calculation program depending on intermediate results or other additional conditions. This feature of the computer (self-control), with high speed (up to 1,000,000 operations per second), allows you to perform very complex calculations, control technological processes, and perform logical and mathematical processing of the results of an experiment or clinical analysis continuously during the study (see Cybernetics).

According to the principle of operation, computers are divided into analog and digital. In analog computers, figures or processes that are subject to mathematical or logical processing are replaced by the corresponding continuous values ​​of electric currents or voltages, with which the necessary operations are performed. The accuracy of calculations is determined by measurement errors and lies within 10-0.1%. Analog computers are mainly used to solve integrated and differential equations, modeling and process control in real time, especially if high accuracy is not required.

In digital computers, calculations are performed using elements that are in a finite number of discrete states (usually in two, ten). Therefore, before input, continuous processes must be presented in digital form, which is carried out using special analog-to-code converters. The accuracy of calculations is determined by the bit depth - the number of digits (digits) in one "memory" cell (usually 7-10 decimal digits). Practically on digital computers, any required accuracy can be achieved with the help of a program.

A modern computer consists of the following main units. 1. An arithmetic unit where basic operations are performed. 2. Storage device (distinguish between long-term and operational). Long-term storage stores data on magnetic disks, drums, tapes or punched cards. The storage time of information and the volume of the long-term storage device are practically unlimited, however, the speed of access is the lower, the larger the volume. Random access memory is usually carried out on ferromagnetic elements, cathode ray tubes or electron tubes. The search time for information in the random access memory is about millionths of a second, but its volume is always limited. 3. Input device. 4. Data output device. Input is carried out from punched tape, punched cards, magnetic tapes. The output in most cases is performed by a direct-printing device (in modern computers, data input and output are the slowest operations). 5. The control device ensures the automatic operation of all computer devices in accordance with the program.

Typical modern computers of medium power require a room of 40-60 m 2, 5-20 service personnel, food 10-20 kw.

The main fields of application of computers in medicine and biology are as follows. 1. Diagnosis of diseases, determination of the prognosis and selection of the optimal treatment option, classification of biological objects. 2. Automatic processing of experimental and clinical data (isolation of regular components in electroencephalograms and neurograms, spectral and correlation analysis of biological processes, counting and classification of blood cells or histological preparations, analysis of radiography data, processing of X-ray examination data). 3. Implementation of mathematical and physical models (modeling of neural networks, behavior, metabolism in the body or individual cells, individual organs or systems of the body, the behavior of animal populations). 4. Stereotactic calculations during operations on the human brain. 5. Automation of processing of medical archival materials. 6. Prediction of pharmacological properties of substances by their physical and chemical characteristics. 7. Automatic control artificial respiration and circulation during operations and when monitoring patients in serious condition. 8. Planning and automation of long and expensive experiments. There is a tendency to further expand the areas of application of computers in biology and medicine.

Integers are the simplest numerical data with which the computer operates. There are two representations for integers: unsigned (only for non-negative integers) and signed. Obviously, negative numbers can only be represented in signed form. Integers are stored in computers fixed point format.

Representation of integers in unsigned integer types.

For unsigned representation, all digits of the cell are assigned to the representation of the number itself. For example, in a byte (8 bits) you can represent unsigned numbers from 0 to 255. Therefore, if you know that a numerical value is non-negative, then it is more profitable to consider it as unsigned.

Representation of integers in signed integer types.

For a signed representation, the most significant (left) bit is assigned to the sign of the number, the remaining digits are assigned to the number itself. If the number is positive, then 0 is placed in the sign bit, if negative - 1. For example, signed numbers from -128 to 127 can be represented in a byte.

Direct number code.

The representation of a number in the usual form "sign" - "value", in which the highest bit of the cell is assigned to the sign, and the rest to the number in the binary system, is called direct code binary number. For example, direct code binary numbers 1001 and - 1001 for an 8-bit cell is 00001001 and 10001001 respectively.

Positive numbers in the computer are always represented using a direct code. The direct code of the number completely coincides with the entry of the number itself in the cell of the machine. The direct code of a negative number differs from the direct code of the corresponding positive number only in the content of the sign bit. But negative integers are not represented in a computer using a direct code, the so-called additional code .

Additional number code.

Additionalthe code positive number is equal to the direct code of this number. The complementary code of a negative number m is 2 k -|m|, where k is the number of digits in the cell.

As already mentioned, when representing non-negative numbers in unsigned format, all digits of the cell are assigned to the number itself. For example, writing the number 243=11110011 in one byte with unsigned representation will look like this:

When representing integers with a sign, the leading (left) digit is assigned to the sign of the number, and under the actual number remains one digit less. Therefore, if the above state of the cell is considered as a record of a signed integer, then for the computer in this cell the number is written - 13 (243+13=256=28).

But if the same negative number is written into a cell of 16 digits, then the contents of the cell will be as follows:

1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 1

Sign digit The question arises: for what purpose are negative numbers written in the form of an additional code and how to get the additional code of a negative number? Additional code used to simplify arithmetic operations. If the computer worked with direct codes of positive and negative numbers, then when performing arithmetic operations, a number of additional actions would have to be performed. For example, when adding, you would need to check the signs of both operands and determine the sign of the result. If the signs are the same, then the sum of the operands is calculated and the same sign is assigned to it. If the signs are different, then the smaller number is subtracted from the larger number and the sign of the larger number is assigned to the result. That is, with such a representation of numbers (in the form of only a direct code), the addition operation is implemented through a rather complex algorithm. If negative numbers are represented as an additional code, then the operation of addition, including those of a different sign, is reduced to bitwise addition.

For computer representation of integers, one, two, or four bytes are usually used, that is, a memory cell will consist of eight, sixteen, or thirty-two bits, respectively.

Algorithm for obtaining an additional code of a negative number.

To obtain an additional k-bit code of a negative number, it is necessary

• 1. the module of a negative number is represented by a direct code in k binary digits;
• 2. invert the value of all bits: replace all zeros with ones, and ones with zeros (thus, a k-bit reverse code of the original number is obtained);
• 3. add one to the received return code.

We get the 8-bit additional code of the number - 52:

• 00110100 - number |-52|=52 in direct code
• 11001011 - number - 52 in reverse code
• 11001100 - number - 52 in additional code

You may notice that the representation of an integer is not very convenient to represent in the binary system, so the hexadecimal representation is often used:

Representation of real numbers in a computer.

To represent real numbers in modern computers accepted way of presenting floating point. This way of representation is based on the normalized (exponential) notation of real numbers.

As with integers, when representing real numbers in a computer, the binary system is most often used, therefore, the decimal number must first be converted to the binary system.

Normalized notation for a number.

Normalizedrecord non-zero real number is a record of the form

where q is an integer (positive, negative, or zero) and m is a proper p-number whose first decimal digit is non-zero, i.e. Here m is called mantissa numbers, q - in order numbers.

• 1. 3,1415926 = 0, 31415926 * 10 1 ;
• 2. 1000=0,1 * 10 4 ;
• 3. 0,123456789 = 0,123456789 * 10 0 ;
• 4. 0.0000107 8 \u003d 0.1078 * 8 -4; (the order is written in the 10th system)
• 5. 1000,0001 2 = 0, 100000012 * 2 4 .

Since the number zero cannot be written in the normalized form in the form in which it was defined, we assume that the normalized notation of zero in the 10th system will be as follows:

0 = 0,0 * 10 0 .

Normalized exponential notation numbers is a notation of the form a= m*P q , where q is an integer (positive, negative, or zero) and m is a P-number that has whole part consists of one number. Here the (m-integer part) is called mantissa numbers, q - in order numbers.