1. Information coding. Encoding methods

Encoding of information. In the process of transforming information from one form of representation (sign system) to another, coding. The encoding tool is a correspondence table, which establishes a one-to-one correspondence between signs or groups of signs of two different sign systems.

In the process of exchanging information, it is often necessary to perform operations coding And decoding information. When you enter an alphabet character into a computer by pressing the corresponding key on the keyboard, it is encoded, i.e., converted into computer code. When a sign is displayed on a monitor screen or printer, the reverse process occurs - decoding, when the sign is converted from a computer code into a graphic image.

Image and sound coding. Information, including graphic and audio, can be presented in analog or discrete form. With analog representation, a physical quantity takes on an infinite number of values, and its values ​​change continuously. With a discrete representation, a physical quantity takes on a finite set of values, and its value changes abruptly.

An example of an analog representation graphic information This could be, say, a painting whose color changes continuously, or a discrete one - an image printed using an inkjet printer and consisting of individual dots of different colors.

An example of analog storage of audio information is vinyl record (soundtrack changes its shape continuously), and discrete - an audio compact disc (the audio track of which contains areas with different reflectivity).

Graphic and audio information from analogue to discrete form is converted by sampling, i.e., partitioning a continuous graphic image and a continuous (analog) sound signal into individual elements. The sampling process involves encoding, i.e., assigning each element a specific value in the form of a code.

Discretization - it is the transformation of continuous images and sound into a set of discrete values, each of which is assigned a value of its code.

Coding of information in living organisms. Genetic information determines the structure and development of living organisms and is inherited. Genetic information is stored in the cells of organisms in the structure of DNA (deoxyribonucleic acid) molecules. DNA molecules are made up of four different components (nucleotides) that form the genetic alphabet.

The human DNA molecule includes about three billion nucleotide pairs, and it encodes all the information about the human body: its appearance, health or susceptibility to disease, abilities, etc.

2. Basic characteristics of the computer (bit capacity, clock frequency, amount of RAM and external memory, performance, etc.)

CPU. The most important characteristic of a processor that determines its performance is its frequency, i.e. the number of basic operations (for example, addition operations of two binary numbers), which the processor produces in 1 second. In just over twenty years, processor clock speeds have increased 500-fold, from 4 MHz (8086 processor, 1978) to 2 GHz (Pentium 4 processor, 2001).

Another characteristic of the processor that affects its performance is bit depth processor. The processor capacity is determined by the number of binary bits that the processor processes in one clock cycle. The processor capacity has increased 8 times over 20 years. The first domestic school computer, UAGATF (1985), had an 8-bit processor, compared to the modern Pentium processor 4 bit is equal to 64 bits.

RAM (internal) memory. RAM consists of many cells, and each cell has its own unique binary address. Each memory cell has a capacity of 1 byte.

In personal computers, the size of the processor address space and the amount of actually installed RAM almost always differ. For example, the amount of addressable memory can reach 4 GB, and the amount of actually installed RAM will be significantly less - say, UvsegoF 64 MB

RAM is implemented in hardware in the form of memory modules of various types (SIMM, DIMM) and different sizes (from 1 to 256 MB). The modules vary in their geometric dimensions: legacy SIMMs have 30 or 72 pins, while modern DIMMs have 168 pins.

Long-term (external) memory. Storage media of various information capacities are used as external memory: floppy disks (1.44 MB), hard disks (up to 50 GB), optical CD-ROMs(650 MB) and DVD (up to 10 GB). The slowest of them in terms of data exchange speed are floppy disks (0.05 MB/s), and the fastest are hard disks (up to 100 MB/s).

Computer performance. Computer performance is its integral characteristic, which depends on the frequency and bit capacity of the processor, the amount of RAM (internal) and long-term (external) memory and data exchange speed. Computer performance cannot be calculated; it is determined during testing by the speed of performing certain operations in a standard software environment.

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1. Qualitative and quantitative characteristics of information. Properties of information (novelty, relevance, reliability, etc.). Units for measuring the amount of information

Information in biology. In biology, the concept information associated with the appropriate behavior of living organisms. Concept information in biology it is also used in connection with studies of the mechanisms of heredity. Genetic information is inherited and stored in all cells of living organisms. Information in cybernetics. In cybernetics (control science) the concept information used to describe control processes in complex systems (living organisms or technical devices). Information and knowledge. A person receives information from the surrounding world using the senses, analyzes it and identifies significant patterns through thinking, and stores the received information in memory. The process of systematic scientific knowledge the surrounding world leads to the accumulation of information in the form of knowledge (facts, scientific theories, etc.). Thus, from the point of view of the cognition process, information can be considered as knowledge.

Properties of information. Participants in the discussion must speak the language in which communication is conducted, then the information will be understandable. Only provided that the information useful, the discussion acquires practical value. Examples of transmitting and receiving useless information include some conferences and chats on the Internet.

The term Mass Media (newspapers, radio, television) is widely known, which convey information to every member of society. It is imperative that such information be reliable And relevant. False information misleads members of society and can cause social unrest. Outdated information is useless, which is why no one except historians reads last year's newspapers.

In order for a person to correctly navigate the world around him, he needs full And accurate information. The task of obtaining complete and accurate information faces science. A person receives a full and exact information about nature, society and technology in the learning process.

Units for measuring the amount of information. Behindunit of information quantity such an amount of information is accepted that contains a message that reduces the uncertainty of knowledge by half. This unit is called bit.

The next largest unit of measurement for the amount of information is byte, and

1 byte = 2 3 bits = 8 bits.

Units for measuring the amount of information that are multiples of a byte are entered as follows:

1 KB = 2 10 bytes = 1024 bytes;

1 MB = 2 10 KB = 1024 KB;

1 GB = 2 10 MB = 1024 MB.

2. External computer memory. Various types of storage media, their characteristics (information capacity, speed, etc.)

The main function of a computer's external memory is the ability to long-term store a large amount of information (programs, documents, audio and video clips, etc.). A device that provides recording/reading of information is called storage device or disk drive, and the information is stored on media(for example, floppy disks).

In floppy magnetic disk drives (FLMD or floppy disks) and hard magnetic disk drives (HDD or hard drives), The basis for recording, storing and reading information is the magnetic principle, and in laser disk drives it is the optical principle.

Flexible magnetic disks. Flexible magnetic disks are placed in a plastic case. This storage medium is called a floppy disk. The floppy disk is inserted into the disk drive, which rotates the disk at a constant angular speed. The magnetic head of the drive is installed on a specific concentric track of the disk, onto which information is written (or read).

In order to preserve information, flexible magnetic disks should be protected from exposure to strong magnetic fields and heat, as this can lead to demagnetization of the media and loss of information.

Hard magnetic disks. Hard magnetic disks are several dozen disks placed on one axis, enclosed in a metal case and rotating at high angular speed. Due to the many tracks on each side of the disks and the large number of disks, the information capacity of hard disks can be tens of thousands of times greater than the information capacity of floppy disks and reach 50 GB.

Laser drives and disks. Laser disk drives use the optical principle of reading information. On laser discs CD (CD - Compact Disk, compact disc) and DVD (DVD - Digital Video Disk, digital video disc), information is recorded on one spiral-shaped track (like on a gramophone record), containing alternating sections with different reflectivity. The laser beam falls on the surface of the rotating disk, and the intensity of the reflected beam depends on the reflectivity of the track section and takes on the values ​​0 or 1.

To ensure the safety of information, laser discs must be protected from mechanical damage (scratches), as well as from contamination.

For the user, some technical characteristics of various information storage devices are essential: information capacity, speed of information exchange, reliability of its storage (Table 2).

Storage and storage media

Type Capacity Speed(Mb/s) Danger

NGMD 1.44 MB 0.05 Magn. fields

HDD up to 50GB up to 100 Beats

CD-ROM 650MB up to 7.8 Scratches and

DVD-ROM up to 17GB up to 6.8 | contamination

1. Information and information processes in nature, society, technology. Human information activity

I By the end of the 20th century. An information picture of the world began to take shape, first within the framework of cybernetics, and then computer science. The structure and functioning of complex systems of various natures (biological, social, technical) turned out to be impossible to explain without considering the general patterns of information processes.

Receiving and converting information is a condition for the life of any organism. Even the simplest single-celled organisms constantly perceive and use information, for example, about the temperature and chemical composition of the environment to select the most favorable living conditions.

Any living organism, including humans, is a carrier of genetic information that is inherited. Genetic information is stored in all cells of the body in DNA molecules, |

A person perceives the world around him (receives information) with the help of his senses (vision, hearing, smell, touch, taste). To navigate correctly in the world, he remembers the information received (stores information). In the process of achieving any goals, a person makes decisions (processes information), and in the process of communicating with other people, he transmits and receives information. Man lives in a world of information.

Processes associated with receiving, storing, processing and transmitting information are called information processes.

Information processes are characteristic not only of living nature, humans and society, but also of technology. Man has developed technical devices, such as computers, that are specifically designed for automatic processing information.

2. Object-oriented programming. Objects: properties and methods. Object classes

object-oriented programming is currently

time the most popular programming technology. Object-oriented programming languages ​​are Visual Basic, Visual Basic for Application (VBA), Delphi, etc.

Encapsulation. The basic unit of object-oriented programming is the object, which contains encapsulates, both the data that describes it (properties) and the means for processing this data (methods).

Object classes and instances class, objects encapsulating the same list of properties and methods are combined into classes. Each individual object is an instance of the class. Instances of a class can have different property values.

for example, in the Windows & Office environment in the Word application there is a class of objects document, which is denoted as follows:

An object class can contain many different documents, each with its own name. For example, one of the documents may be named Proba.doc
Documents ("Proba.docФ")

Objects in applications form some kind of hierarchy. At the top of the object hierarchy is application. Thus, the Word application object hierarchy includes the following objects: application ( application), document(Documents), fragment document (Selection), symbol (Character), etc.

A full reference to an object consists of a series of names of objects nested sequentially within each other. The separators for object names in this series are dots; the series begins with the highest-level object and ends with the name of the object of interest to us.

Application. Documents ("Probe.doc")

Object methods. In order for an object to perform any operation, a method must be specified. Many methods have arguments that allow you to set parameters for the actions to be performed. To assign specific values ​​to arguments, a colon and an equal sign are used, and arguments are separated by a comma.

Apply Command Syntax object method next:

Object.Method arg1:=value, arg2:=value

For example, the operation of opening a ripo6a.doc document in Word must contain not only the name of the Open method, but also an indication of the path to the file to be opened (the FileName method argument must be assigned a specific value):

Documents(). Open FileName: ="C: DocumentsProba.doc"

Object properties. To change the state of an object, you need to define new values ​​for its properties. To assign a specific value to a property, use the equal sign. Syntax for setting a value object properties next:

Object.Property = PropertyValue

One of the object classes is the Characters() class. Instances of the class are numbered:

Characters (1), Characters (2) etc. Set in a text fragment (object selection) for the first character (object Characters (1)) style bold(property Bold).

The Bold property has two values ​​and can be set (True) or unset (False). The values ​​True and False are language keywords.

CPU. The processor can process different kinds information: numerical, textual, graphic, video and audio. The processor is an electronic device, so various types of information must be processed in it in the form of sequences of electrical impulses.

Such sequences of electrical pulses can be written as sequences of zeros and ones (there is an impulse - one, no impulse - zero), which are called machine language.

Information input and output devices. Human does not perceive electrical impulses and very poorly understands information presented in the form of sequences of zeros and ones; therefore, the computer requires special input and output devices.

Input devices translate information from human language into computer machine language, and output devices, on the contrary, make the information presented on the computer. machine language, accessible to human perception.

Information input devices. Entering numeric and text information is done using keyboards. To enter graphic information or work with the graphical interface of programs, manipulators like mouse(for desktop personal computers) and trackball or touchpad(for laptop computers).

If we want to enter a photograph or drawing into the computer, we use a special device - scanner. Currently, they are becoming more widespread digital, cameras(cameras and video cameras) that form images in computer format.

Operating processor memory

highway

device Input long memory set output.

keyboard ngmd monitor

mouse cd-rom printer

scanner dvd-rom plotter

Designed for input of audio information microphone, connected to the input of a special sound card installed on the computer.

It is more convenient to manage computer games using special devices - game controllers(joysticks).

Information output devices. The most versatile output device is monitor, on the screen of which numerical, text, graphic and video information is displayed.

To save information in the form of a hard copy on paper, it is used Printer, and for printing complex drawings, drawings and large format diagrams on paper - plotter(plotter).

Working and long-term memory. On a computer, information is stored in operational(internal) memory. However, when you turn off the computer, all information from RAM is erased.

Long-term storage of information is ensured external memory. External memory devices are usually floppy disk drives (FMD), hard disk drives (HDD) And optical drives (CD-ROM And DVD-BOM).

Highway. Exchange of information between separate devices computer is produced by highways(Fig. 8).

Connecting your computer to the network. A person constantly exchanges information with people around him. A computer can exchange information with other computers using local and global computer networks. For this purpose it includes network card And modem.

2 .The algorithm allows formalize completing the task. Let's assume that the user needs to edit the text and get the text Information ModelF from the text Information ModelF.

Writing an algorithm in natural language . Let's write down the necessary sequence of actions, i.e. the Text Editing algorithm, on natural

language, which is understandable to a person (computer user):

1) highlight the word informational+ space;

2) cut out this fragment;

3) place the cursor at the position after the word model+ space;

4) insert a piece of text.

Writing an algorithm in an algorithmic language.

Each command of the algorithm must uniquely determine the action of the performer, i.e. the algorithm must be accurate. However, natural language is not very suitable for writing algorithms, since it does not have sufficient rigor and certainty when writing commands.

To achieve the required accuracy and rigor, the algorithm should be formalized, i.e., written in one of formal languages. IN school computer science is often used as such a formal language algorithmic language.

Let's write the algorithm Editing text in an algorithmic language:

alg Editing text

given information model

necessary information model

beginning select characters from 1 to 15

cut

set the cursor to position 7

insert
Graphical representation algorithm. To make the algorithm more visual, they often use flowcharts. The block diagram (Fig. 9) clearly shows the structure of the algorithm, according to which it is convenient for the performer (human) to track the process of its execution.

1. Software control computer operation. Computer software

Data and programs. Numerical, textual, graphic and audio information can be presented and processed on a computer in the form of data. In order for the processor to know what to do with the data, how to process it, it must receive a specific command(instructions). For example, Add two numbers Ф or Replace one character with another Ф. Usually, to solve a problem, the processor requires not a single command, but a sequence of them. The sequence of commands that a computer executes while processing data is called program.

Software. Over the course of several decades, programs needed to process various data have been created. The totality of required programs is software

computer.operating system is a basic and necessary component of computer software; without it, a computer cannot operate in principle.

To perform specific work on a computer (creating texts and drawings, processing numerical data, etc.) you need application software. Application software can be divided into two groups of programs: systems

programming And applications.

Programming systems are tools for professional programmers to develop programs in various programming languages ​​(Basic, Pascal, C, etc.). Currently, visual programming systems have appeared (Visual Basic, Borland Delphi, etc.), which allow even a novice computer user to create simple programs. Applications provide the user with the opportunity to process text, graphic, numerical, audio and video information, as well as work in computer networks without knowing programming. Almost every computer user needs applications general purpose, which include: text and graphic editors, spreadsheets, database management systems, as well as applications for creating multimedia presentations. Due to rapid development global and local computer networks, various communication programs. Due to the widespread distribution of computer viruses, they can be classified as a separate group. antivirus programs.

For professional purposes, qualified computer users use special purpose applications. These include computer graphics systems, computer-aided design (CAD) systems, accounting programs, computer dictionaries and automatic translation systems, etc. All larger number users applies training programs for self-education or educational process. First of all, these are training programs foreign languages, tutoring programs and tests in various subjects, etc. Various multimedia applications (encyclopedias, reference books etc.) on laser discs containing a huge amount of information and means for quickly searching it.

A fairly large number of users begin their acquaintance with a computer with computer games, which come in a variety of types: logical, strategic, sports, etc.

2. Basic types and methods of organizing data (variables and arrays)

Variables. In algorithmic and object-oriented programming languages ​​(in particular, in the Visual Basic language) variables play a vital role. They are designed for storing and processing data in programs.

Variables are set names, defining the memory areas in which they are stored meanings. data various types (integer or real numbers, sequences of characters, logical values, etc.). The type of variables is determined by the type of data, which can be the values ​​of the variables. Variable values numeric types(Byte, Integer, Long, Single, Double) are numbers. Boolean variables can be True or False. Values string variables (String) are sequences of characters, etc. Over various data types, and therefore variables are allowed various operations. Thus, arithmetic operations are possible on numeric variables, logical operations on logical variables, character string conversion operations on string variables, etc.

Different types of data require different numbers of cells (bytes) to be stored in the computer's RAM. Thus, to store an integer in the range from 0 to 255 in variables of the Byte type, one memory cell (one byte) is sufficient; to store a real number with double precision in variables of the Double type requires eight cells (eight bytes), and to store character strings in String type variables - one cell per character. The name of any variable (identifier) ​​is unique and cannot change during program execution. The variable name can consist of various characters (Latin and Russian letters, numbers, etc.), but must begin with a letter and not include the U.F (dot) sign. The number of characters in the name cannot be more than 255. For example, a numeric variable can be called A or Number, and a string variable can be called A or String.

The simplest way to specify the type of a variable (its “declaration”) is to append a specific variable to the variable name suffix. For example, numeric type variable Integer can be specified as A%, and a string variable of type String can be specified as A$. A variable can get or change its value using assignment operator:Let's VariableName = Expression

The Let keyword is not used in most cases. The variable receives a value equal to the value of the expression (arithmetic, string, or Boolean).

For example, after executing a program fragment intA = 3 intB = 4 intC = intA"2 + intB"2

the integer variable intC will take the value equal to the number 25.

Arrays. one-dimensional, which can be represented in the form of a one-dimensional table, and two-dimensional(they are presented in the form of a two-dimensional table).

Arrays can be of different types: numeric, string etc.

An array consists of a numbered sequence of elements. The numbers in this sequence are called indexes. Each of these elements is a variable, that is, it has a name and a value, and therefore the array can be called variable with index.

For example, a one-dimensional string array strA (I i, containing letters of the Russian alphabet, can be represented as the following table:

I 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 E 33

A(I) A B C D E E F F H H I J K L M N O PEIA

The index can take any integer value (in this case from 1 to 33). An array element is accessed by its name, which consists of the array name and the index value, for example strA(5).

Each array element can have its own value. Thus, the value of the element of the string array s t rA (5) discussed above is the string d.

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1. Text editor. Purpose and main functions

Text editors - These are programs for creating, editing, formatting, saving and printing documents. A modern document may contain, in addition to text, other objects (tables, diagrams, pictures, etc.).

More advanced text editors that have a whole range of capabilities for creating documents (for example, searching and replacing characters, spell checkers, inserting tables, etc.) are sometimes called word processors. An example of such a program is Word from office suite Microsoft Office.

Powerful word processing programs - desktop publishing systems - are intended for preparing documents for publication. Example similar system- Adobe PageMaker.

Editing - transformation that adds, deletes, moves, or corrects document content. Editing a document is usually done by adding, deleting, or moving characters or pieces of text.

The object-oriented approach makes it possible to implement mechanism for embedding and embedding objects(OLE - Object Linking embedding). This mechanism allows you to copy and paste objects from one application to another. For example, when working with a document in the Word text editor, you can embed images, animation, sound and even video clips into it and thus get a multimedia document from a regular text document.

Formatting - A transformation that changes the presentation form of a document. At the beginning of working on a document, it is advisable to set page parameters: its format (size), orientation, margin size, etc.

Paragraph formatting. A paragraph is one of the main objects of a text document. In computer documents, a paragraph is any text that ends with a control character (marker) for the end of the paragraph. Entering the end of a paragraph is achieved by pressing the (Enter) key and is indicated by the C symbol.

In the process of formatting a paragraph, parameters are set for its alignment (alignment reflects the position of the text relative to the boundaries of the page margins), indents (the entire paragraph can have indents on the left and right) and spacing (the distance between the lines of the paragraph), indentation of the red line, etc.

character formatting. Symbols are letters, numbers, spaces, punctuation marks, special characters such as @, *, &. Symbols can be formatted (change their appearance) by specifying font, size And outline.

Font - a complete set of characters of a specific style, including uppercase and lowercase letters, punctuation marks, special characters, numbers and arithmetic symbols. Each historical period and different countries are characterized by a font of a certain design. Each font has its own name, for example Times New Roman, Anal, Courier, etc.

Fonts differ in the way they are presented on a computer. raster And vector. Methods are used to represent raster fonts raster graphics, font characters are groups of pixels. Bitmap fonts can only be scaled by certain factors.

In vector fonts, characters are described mathematical formulas and their arbitrary scaling is possible. Among vector fonts, TrueType fonts are the most widely used.

Font size. The unit of font size is the point (1 pt = 0.376 mm). The default font in Word is Times New Roman, 12 pt.

Inscription. In addition to the normal (usual) style of characters, bold is usually used, italic And bold italic.

The file format determines how text is stored in the file. Simplest format text file(TXT) contains only characters (numeric character codes), while other formats (DOC, RTF) contain additional control numeric codes that provide text formatting.

2. Binary coding of text information. Various Cyrillic encodings

Since the late 60s, computers have increasingly become used for processing text information, and currently the bulk of personal computers in the world. (and most of the time) is busy processing textual information. ...

Traditionally, a lot of information is used to encode one character! equal to 1 byte, i.e. 1=1byte=8bits.

If we consider symbols as possible events, we can calculate how many different symbols can be encoded: N = 2 1 =2 8 - 256.

This number of characters is quite sufficient to represent text information, including uppercase and capital letters of the Russian and Latin alphabet, numbers, signs, graphic symbols, etc.

Coding consists of assigning each character a unique binary code from 0 to 255 or a corresponding binary code from 00000000 to 11111111. Thus, a person distinguishes characters by their drawing, and the computer - according to their code.

When text information is entered into a computer, it is binary encoded; the image of the symbol is converted into its binary code. The user presses a key with a symbol on the keyboard, and a certain sequence of eight electrical impulses (binary code of the symbol) is sent to the computer. The symbol code is stored in the computer's RAM, where it occupies one cell.

In the process of displaying a symbol on a computer screen, the reverse process is performed - decoding, i.e. converting the symbol code into its image. "It is important that assigning a specific code to a character is a matter of convention, which is recorded in the code table. The first 33 codes (from 0 to 32) do not indicate characters, but operations (line feed, entering a space, etc.).

Codes from 33 to 127 are international and correspond to characters of the Latin alphabet, numbers, arithmetic operations and punctuation marks.

Codes from 128 to 255 are national, i.e. e-in national In encodings, different characters correspond to the same code. Unfortunately, there are currently five different encoding tables for Russian letters (KOI-8, SR1251, SR866, Mae, ISO), so texts created in one encoding will not display correctly in another.

Each encoding is specified by its own code table. To the same thing binary code Different encodings have different symbols assigned to them.

Recently, a new international standard, Unicode, has appeared, which allocates not one byte for each character, but two, and therefore with its help you can encode not 256 characters, but - 2 18 = 65,536 different characters

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1. Graphic editor. Purpose and mainfunctions

A graphics editor is a program for creating, editing and viewing graphic images. Graphic editors - two categories: raster and vector.

Raster graphic editors. Raster graphic editors are the best means of processing photographs and drawings. Raster graphics editors range from simple ones, such as the standard Paint application, to powerful professional graphics systems, such as Adobe Photoshop and CorelPhoto-Paint.

A raster image is stored using dots of different colors (pixels) that form rows and columns. Any pixel has a fixed position and color. Storing each pixel requires a certain number of bits of information, which depends on the number of colors in the image. The quality of a raster image is determined by the size of the image (the number of horizontal and vertical pixels) and the number of colors that the pixels can accept.

Raster images are very sensitive to scaling (enlargement or reduction). When raster image decreases, several neighboring points turn into one, so legibility is lost small parts Images. When the image is enlarged, the size of each dot increases and a step effect appears, which is visible to the naked eye.
Vector graphic editors.

You come across vector graphics when you work with computer drawing and computer-aided design systems, with three-dimensional graphics processing programs. CorelDRAW and Adobe Illustrator are common.

Vector images are formed from objects (point, line, circle, etc.), Graphic primitive dot is given by its coordinates (X, Y), line - origin coordinates (XI, U1) and end (X2 , U2), circle - center coordinates (X, Y) and radius (L), rectangle - the size of the sides and the coordinates of the upper left corner (XI, Y1) and the lower right corner (X2, Y2), etc. A color is also assigned for each primitive.

Graphic editors have a set tools for creating or drawing the simplest graphic objects: straight line, curve, rectangle, ellipse, polygon, etc. Highlighting tools. In graphic editors, various operations are possible on image elements: copying, moving, deleting, rotating, resizing, etc. The selection procedure is similar to the drawing procedure.

Picture Editing Tools allow you to make changes to the drawing: erase parts of it, change colors, etc. The tool is used Eraser, IN vector editors Editing an image is only possible by removing the objects included in the image entirely. The color change operation can be done using the menu Palette, containing a set of colors used when creating or drawing objects.

Text Tools Allows you to add text to a picture and format it.

In vector editors, you can also create text areas for entering and formatting text. In addition, captions for drawings are entered using the so-called callout various forms.

Scaling Tools in raster graphics editors, they make it possible to increase or decrease the scale of an object’s representation on the screen without affecting its actual size. This tool is usually called Magnifier.

In vector graphics editors, it is easy to change the actual dimensions of an object using the mouse.

2. Logical multiplication. Truth table

In the algebra of logic, combining two (or more) statements into one using the conjunction UiF is called logical multiplication operation or conjunction.

A compound statement formed as a result of the operation of logical multiplication (conjunction) is true if and only if the simple statements included in it are true.

The operation of logical multiplication (conjunction) is usually denoted either by the symbols U l F, U & F. or a multiplication sign< Х Образуем составное высказывание F, which results from the conjunction of two simple statements:

WITH from the point of view of propositional algebra, we wrote down the formula for the logical multiplication function, the arguments of which are the logical variables A and B, taking the values true(1) and lie (Oh).

The logical multiplication function itself F can also take only two values ​​- true(1) and false (0). The value of a logical function is determined using the truth table of this function

Using the truth table, it is easy to determine the truth of a compound statement formed using the operation of logical multiplication. Consider, for example, the compound statement U2X2 = 4 and ZHZ = 10F. The first simple statement is true (A-1), and the second simple statement is false (IN- 0); From the table we determine that logical function takes on the value false (F== O), i.e. this compound statement is false.

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1. Spreadsheets. Purpose and main functions

Spreadsheet - is a numerical data processing program that stores and processes data in rectangular tables.

The spreadsheet consists of columns And lines. Column headings are designated by letters or combinations of letters (A, G, AB, etc.), row headings are designated by numbers (1, 16, 278, etc.). Cell - the intersection of a column and a row.

Each table cell has its own own address. Spreadsheet cell address made up of a column header and a row header, for example: A1, F123, L7. The cell with which some actions are performed is highlighted with a frame and called active.

Data types. Spreadsheets allow you to work with three main types of data: number, text And formula.

Numbers in spreadsheets Excel can be written in regular numeric or exponential format, for example: 195.2 or 1.952D +02. By default, numbers are aligned to the right in a cell. This is explained by this. that when placing numbers under each other (in a table column), it is convenient to have alignment by digits (units under units, tens under tens, etc.).

Text in electronic Excel tables is a sequence of characters consisting of letters, numbers and spaces, for example the entry<32 МбайтФ является текстовой. По умолчанию текст выравнивается в ячейке по левому краю. Это объясняется традиционным способом письма (слева направо).

The formula must begin with an equal sign and can include numbers, cell names, functions (Mathematical, Statistical. Financial, Date and time I, etc.) and signs of mathematical operations. For example, the formula U=A1+D2F provides the addition of numbers stored in cells A1 and B2, aformula <=А1*5Ф - multiplying the number stored in cell.41 by 5. When you enter a formula in the cell, it is not the formula itself that is displayed, but the result of calculations using this formula. If the initial values ​​included in the formula change, the result is recalculated immediately.

Absolute and relative links. Formulas use references to cell addresses. There are two main types of links: relative And absolute. The differences between them appear when you copy a formula from the active cell to another cell.

Relative link the formula uses | to specify the cell address, calculated relative to the cell in which the formula is located. When you move or copy a formula from the active cell, relative references are automatically updated based on the new position of the formula. Relative links have the following form: A1, ВЗ.

Absolute link in the formula is used for | specifying a fixed cell address. When changing-| When copying or copying a formula, absolute references f do not change. In absolute references, the immutable cell address value is preceded by a dollar sign (for example, $A$1).

If the dollar sign precedes a letter (for example: $ A), then the column coordinate is absolute, and the row coordinate is relative. If the dollar symbol comes before the number | scrap (for example, A$1), then, on the contrary, the column coordinate is relative, and the row coordinate is absolute. Such links are called sdeshannyli. ; .

Let, for example, in cell C1 the formula is written.mA$1+$B1, which, when copied to cell D2 takes the form =B$1+$B2. Relative links g changed when copied, but absolute ones did not. . Sort by search data. Spreadsheets allow you to sort data. Data I spreadsheets are sorted in ascending or descending order. When sorting, data is arranged in a certain order. You can perform nested sorts, i.e., sort data by several columns, and assign a sorting sequence for the columns.

It is possible to search for data in spreadsheets in accordance with the specified conditions - filters. Filters are defined using search terms (more, less, equal etc.) and values ​​(200, 10 etc.). For example, more than 100. As a result of the search, those cells will be found that contain data that matches the specified filter.

Constructing charts and graphs. Spreadsheets allow you to present numerical data in the form of charts or graphs. Charts come in different types (bar, pie, etc.); The choice of chart type depends on the nature of the data.

2. Internet addressing: domain name system and IP addresses

IP addressing. So that computers can find each other in the process of exchanging information, there is a unified addressing system on the Internet. Every computer connected to the Internet has its own unique 32-bit (binary) IP address.

Using the formula for determining the amount of information, it is easy to calculate that the total number of different IP addresses is more than 4 billion:

N- 2 32 - 4 294 967 296.

In decimal notation, the IP address of a computer on the Internet consists of four numbers separated by dots, each of which lies in the range from O to 255. For example, the IP address of the MTU-Intel server is written as 195.34.32.11.

Have a domain system. It is easy for computers to find each other using a numeric IP address, but it is not easy for a person to remember a numeric address, and for convenience, domain name system(DNS - Domain Name System). The domain name system assigns a unique domain name to the numerical IP address of each computer.

The domain name system has a hierarchical structure: top-level domains - second-level domains - third-level domains. Top-level domains come in two types: geographical (two-letter - each country has a two-letter code) and administrative (three-letter).

Russia owns the geographical domain ru. Long-existing servers may belong to the su (USSR) domain. The administrative domain designation allows you to determine the profile of the organization that owns the domain. The names of computers that are Internet servers include the fully qualified domain name and the actual computer name. Domain names are read from right to left. The rightmost group of letters represents the top-level domain.

Yes, the main server companies Microsoft has a name www.microsoft.com and the MTU-Intel server is dialup.mtu.ru

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1. Databases. Purpose and main functions

Database- This is an information model that allows ordering to store data about a group of objects that have the same set of properties.

Information in databases is stored in an orderly manner.

There are several different types of databases: tabular, hierarchical And network.

Tabular databases. A tabular database contains a list of objects of the same type, that is, objects with the same set of properties. It is convenient to represent such a database in the form of a two-dimensional table.

The columns of such a table are called fields;Database field - This is a table column that contains the values ​​of a particular property.

The table rows are records about object; these records are divided into fields by table columns. Database entry is a table row that contains a set of values ​​for various properties of an object.

Each table must have at least one key field, whose contents are unique to any entry in that table. Key field values ​​uniquely identify each record in the table.

Hierarchical databases. Hierarchical databases can be graphically represented as a tree consisting of objects at various levels. The top level is occupied by one object, the second - by objects of the second level, etc.

There are connections between objects; each object can include several lower-level objects. Such objects are in relation ancestor(object closer to the root) to descendant(a lower-level object), while it is possible for an ancestor object to have no children or to have several of them, while a descendant object must have only one ancestor. Objects that have a common ancestor are called twins.

The hierarchical database is Windows folder directory, with which you can work with by running Conductor.

Network databases. A network database is formed by a generalization of a hierarchical database by allowing objects that have more than one ancestor, i.e., each element of a higher level can be associated simultaneously with any elements of the next level. In general, no restrictions are imposed on the connections between objects in network models.

The network database is actually The World Wide Web global computer network IV-ternet. Hyperlinks link hundreds of millions of documents together into a single distributed network database.

Database management systems (DBMS). For

creating databases, as well as performing search and sorting operations, special programs are designed - database management systems (DBMS).

Thus, it is necessary to distinguish between databases (DBs) themselves - ordered sets of data, and database management systems (DBMS) - programs that manage the storage and processing of data. For example, the Access application, included in the Microsoft Office office suite, is a DBMS that allows the user to create and process tabular databases.

2. Computer viruses: methods of distribution, protection against viruses

Computer viruses are programs that can multiply and secretly insert copies of themselves into files, disk boot sectors and documents.

Currently, there are several tens of thousands of viruses known to infect computers. various operating systems and distributed over computer networks. A mandatory property of a computer virus is the ability to self-copy.

The activation of a computer virus often causes the destruction of programs and data.

According to their habitat, viruses are divided into file, boot, macro viruses And network,

File viruses. File viruses are embedded in executable files (programs) in various ways and are usually activated when they are launched. After running an infected program, viruses are located in the computer’s RAM and remain active (that is, they can infect other files) until the computer is turned off or the operating system is restarted.

Preventive protection against file viruses consists of not executing files received from a dubious source and not previously scanned by anti-virus programs.

Boot viruses. Boot viruses write themselves to the boot sector of the disk. When the operating system is loaded from an infected disk, viruses are introduced into the computer's RAM.

Macroviruses. Macro viruses infect Word document files and Excel spreadsheets. Macro viruses are actually macro commands (macros) that are embedded in a document.

After loading an infected document into an application, macro viruses are constantly present in the computer's memory and can infect other documents. Preventative protection against macroviruses consists of preventing the virus from starting; When you open a document in Word and Excel, you are notified of the presence of macros (potential viruses) in them and are asked to block their downloading. Choosing to prohibit loading macros will reliably protect your computer from infection by macro viruses, but will also disable useful macros contained in the document.

Network viruses. Any common viruses can spread and infect computers over a computer network. This happens, for example, when receiving infected files from file archive servers. However, there are also specific network viruses that use email and the World Wide Web to spread.

The mail * virus is contained in files attached to the mail message. If the recipient of the message opens the attached file (virus), the computer will be infected. This will not happen after reading the email message itself, since it is not the email message that is infected, but the file attached to it.

Preventive protection against email viruses involves not opening files attached to email messages that are received from dubious sources.

Antivirus programs. The most effective anti-virus programs in the fight against computer viruses are those that use various principles for searching and treating infected files.

The most popular and effective antivirus programs are polyphages(for example, AntiVira) Toolkit Pro). The operating principle of polyphages is based on checking files and sectors of disks and RAM and searching them for known and new (unknown to the polyphage) viruses.

Polyphages are capable of checking files as they are loaded into RAM. Such programs are called antivirus programs monitors(for example, AVP Monitor).

The advantages of polyphages include their versatility; the disadvantages are the large size of the antivirus databases they use, which must contain information about the maximum possible number of viruses, which, in turn, leads to a relatively low speed of virus search

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1. Algorithmic structure cycle. Repeat commands. Give an example

In algorithmic structures, a cycle includes a series of commands that are executed repeatedly. This sequence of commands is called body of the cycle.

There are two types of cyclic algorithmic structures:

- loops with counter, in which the body of the loop is executed a certain number of times;

- cycles, with the condition, in which the body of the loop is executed as long as the condition is satisfied.

Algorithmic structure cycle can be recorded in various ways:

In a programming language, such as Visual Basic and VBA, using special instructions that implement various types of loops.

Loop with a counter. When you know in advance how many repetitions of the loop body need to be performed, you can use the cyclic instruction (loop operator with a counter) For. . . Next (Fig. 19).

For... operator syntax Next next:

the line starting with the For keyword is the loop head, and the line with the Next keyword is the end of the loop; Between them are operators that represent the body of the loop.

At the beginning of the loop, the value of the Counter variable is set equal to StartValue. With each pass of the loop, the Counter variable is increased by the step value. If it reaches the value ConValue, then the cycle ends and the following statements are executed.

Conditional loops. It often happens that it is necessary to repeat the body of a loop, but it is not known in advance how many times this must be done. In such cases, the number of repetitions depends on some condition. This loop is implemented using the Do statement. . . Loop.

The loop exit condition can be placed at the beginning, before the loop body, or at the end, after the loop body

The loop exit condition is checked using keywords While or Until. give the same condition the opposite meaning. The While keyword ensures that the loop continues as long as the condition is true, that is, as long as the condition has a value true. In this case the condition is condition for continuing the cycle. lie, The loop will end.

The Until keyword ensures that the loop continues until the condition is met, that is, as long as the condition has a value lie. In this case the condition becomes condition for ending the cycle. As soon as the condition evaluates true, The loop will end.

2. Performing arithmetic operations in the binary number system

Addition. The basis for adding numbers in the binary number system is the table for adding single-digit binary numbers (Table 6).

It is important to pay attention to the fact that when adding two units, a transfer is carried out to the most significant digit. This occurs when the magnitude of a number becomes equal to or greater than the base of the number system.

The addition of multi-bit binary numbers is performed in accordance with the above addition table, taking into account possible transfers from low-order to high-order digits. As an example, let's add the binary numbers POgIPz into a column:

Subtraction. The basis for subtracting binary numbers is the table for subtracting single-digit binary numbers (Table 7). When subtracting a larger number (I) from a smaller number (0), a loan is made from the highest digit. In the table, the loan is designated 1 with a line.

Subtraction of multi-bit binary numbers is implemented in accordance with this table, taking into account possible borrowings in the most significant bits.

Multiplication. Multiplication is based on the multiplication table for single-digit binary numbers (Table 8).

Multiplication of multi-digit binary numbers is carried out in accordance with this multiplication table according to the usual scheme used in the decimal number system, with sequential multiplication of the multiplicand by the next digit of the multiplier. Consider an example of multiplying the binary numbers 110, and Pa:

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1. During development, a complex algorithm can be broken down into separate algorithms called auxiliary. Each auxiliary algorithm describes the solution to a subproblem. Both the main algorithm and auxiliary ones can include basic algorithmic structures: linear, branching and cyclic.

In the process of creating programs in Visual Basic, each form that provides GUI program, corresponds software module. A software module may include two types of procedures: event And are common.

Event procedure is a subroutine that starts executing after a certain event occurs. A software module may contain several event procedures. Each of these procedures begins with the keyword Sub (subroutine - subroutine) and ends with the keywords End Sub.

Program module with event procedures. Let's develop an application (project) that has a graphical interface on a form (Formi) and an associated software module that displays a drawing of a simple house on the form.

Let the house consist of a wall (rectangle) and a roof (triangle). Then in the software module that implements drawing a house on the Forml form, there will be two event procedures -

CTeHa_Click_and_ROOF_Ciick.

Private Sub Wall_click()

Forml.Line (20, l00)-(220, 200), V

private Sub Kpbiuia_Click()

Forml.Line (20, 100)-(220, 100): Forml.Line (20, 100)-(120, 50): Forml.Line (120, 50)-(220, 100) End Sub

To create a graphical interface for the program, place two buttons on Form1 Wall And Roof. Then after launching the program for execution and clicking on the buttons Wall And Roof The corresponding event procedures will be implemented and a picture of a house will appear on the form.

A software module with a general procedure. Let's say that now you need to draw several houses. If you use event procedures, then for each house you will need to write your own procedures, and this is very labor-intensive. In cases where it is possible to identify multiple repeating actions (procedures) in a software module, form general procedures.

The execution of general procedures is not associated with any events; they are called for execution using the Call statement. Each common procedure is given a unique name - procedure name and installed list of inputs And output parameters procedures.

General procedure is a subroutine that begins execution after it is called from another procedure.

An input parameter list is a set of variables whose value must be set before the procedure can be executed.

The list of output parameters is a set of variables whose value is set after the procedure is completed.

Then the procedure call syntax becomes

Call NameProcedure1(List of Parameters) SZ

To implement a graphical interface, we will include another form (Form2) in the project. To draw a house, it is advisable to create a general procedure House(X1, X2, Yl, Y2 As Single), which has only a list of input parameters (coordinates of the wall corners). This procedure has no output parameters.

Let the event procedure Drawing Click () provide drawing of three houses with different values ​​of input parameters, i.e., calls the general procedure House three times with different values ​​of input parameters.

Then the program module associated with the form (Form2) will include the general procedure House (XI, X2, Yl, Y2 As Single) and the event procedure Drawing Click ():

Private Sub House(X1, X2, Yl, Y2 As Single)

Form2.Line (XI, Y1)-(X2, Y2), V

Form2.Line (XI, Y1)-(X2, Yl)"

Form2.Line (X.I, Y1)-((X1 + X2) / 2, Y1:V 2)

Form2.Line ((XI + X2) / 2, Yl / 2)-

Private Sub Drawing_С11с1^()

Call Little house.<10, .50, 50,. J.00) , . ., /

Call House(60, 150, 150, 200)

Call House(160, 300, 80, 200)

To build a graphical interface for the program, we will place a button on Form2. Drawing. In this case, after launching the program for execution and clicking on the button Drawing the event procedure Drawing_Click() will be launched, during which the general procedure House with different parameter values ​​will be called three times and pictures of three different houses will appear on the form.

2. Information modeling. Main types of information models (tabular, hierarchical, network)

Tabular models. One of the most commonly used types of information models is table, which consists of rows and columns.

WITH Using tables, information models are created in various subject areas. The tabular presentation of mathematical functions, statistical data, train and plane schedules, lessons, etc. is widely known.

Tabular information models are most easily created and examined on a computer through spreadsheets and database management systems.

Hierarchical models. We are surrounded by many different objects, each of which has certain properties. However, some groups of objects have the same common properties that distinguish them from objects in other groups.

A group of objects that have the same common properties is called a classols objects. Within a class, subclasses can be distinguished, the objects of which have some special properties, in turn, subclasses can be divided into even smaller groups, etc. This process is called classification process.

When classifying objects, information models are often used that have hierarchical (tree) structure. In a hierarchical information model, objects are distributed across levels, with lower-level elements being part of one of the higher-level elements. For example, the entire animal world is considered as a hierarchical system (phylum, class, order, family, genus, species), computer science is characterized by a hierarchical file system, etc.

Figure 22 shows an information model that allows us to classify modern computers. The resulting information structure resembles a tree that grows from top to bottom (which is why such information models are sometimes called tree-like). Three levels are clearly visible in the structure: from the first, top, which has one element Computers, we descend to the third, lower, having three elements Tabletop, Portable, Pocket.

Network information models. Network information models are used to reflect systems with a complex structure, in which the connection between elements is arbitrary.

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1. Programming language basics (alphabet, operators, data types, etc.)

Programming languages ​​are formal languages ​​that encode algorithms in a form familiar to humans (in the form of sentences). A programming language is determined by specifying an alphabet and a precise description of the rules for constructing sentences (syntax).

The alphabet of a language can include letters, numbers, mathematical symbols, as well as the so-called If keywords. Then (then). Else (otherwise), etc. From the original symbols (alphabet), according to the rules of syntax, sentences are constructed, usually called operators. For example, the conditional jump operator:

If A>B Then X=A+B Else X=A*B

Algorithmic programming languages, or they are also called structural programming languages ​​represent an algorithm as a sequence of basic algorithmic structures - linear, branching, loop.

Various types of algorithmic structures are coded in a programming language using the corresponding operators: branching using the If-Then-Else operator, a loop with a counter using the For-Next operator, etc. Operators, in addition to keywords, sometimes contain arithmetic, string And brain teaser expressions.

Arithmetic expressions can include numbers, variables, arithmetic expression signs, standard features and parentheses. For example, an arithmetic expression that allows you to determine the size of the hypotenuse of a right triangle would be written as follows:

String expressions can include string type variables, strings(strings are any sequence of characters enclosed in quotes) and string functions. For example:

"inf"+M1s1 ("informatics"^ 3, 5) +strA.

Boolean expressions, in addition to logical variables, often include numbers, numeric or string variables, or expressions that are compared with each other using the comparison operator (>,<, =, >-, <= и т. д.).

A Boolean expression takes only one of two values: true or lie. For example: 5 > 3 - true; 2 X 2 = 5 - false.

Logical operations can be performed on the elements of logical expressions, which are designated as follows: logical multiplication - And, logical addition - Or and logical negation - Mot.

Programming languages ​​use different data structures: variable, array etc. Variables are set names, which define the memory areas in which they are stored meanings. Variable values ​​can be data various types (integer or real numbers, strings, logical values). Accordingly, variables are of different types: integers(A%=5), real(A=3.14), string(A$="computer science" 1), brain teaser(A=True).

Arrays are a set of variables of the same type, united by one name. There are arrays one-dimensional, which can be represented as one-dimensional tables, and two-dimensional, which can be represented as two-dimensional tables. Arrays can also be of different types: integer, real, string vn. R,.

Object-oriented programming is a development of structured programming technology, but it It has their characteristic features. The basic unit in object-oriented programming is an object, which contains and encapsulates both the data that describes it (properties) and the means for processing this data (methods).

An important place in object-oriented programming technology is occupied by event. Events can be considered a mouse click on an object, pressing a certain key, opening a document, etc. As a reaction to events, a certain procedure is called, which can change the properties of the object, call its methods, etc.

Object-oriented programming systems typically use a graphical interface to visualize the programming process. It becomes possible to create objects, set their properties and behavior using the mouse.

2. Basics of Hypertext Markup Language (HTML)

Web sites are created using the hypertext markup language HTML (Hyper Text Markup Language). HTML technology consists of inserting control characters (tags) into a regular text document and resulting in a Web page. When loading a Web page, the browser presents it on the screen in the form specified by tags.

Some tags have attributes that define the properties of the tag. Attribute - this is the name of a property that can take on certain values.

To create Web pages, simple text editors are used that do not include document being created text formatting control characters. As such an editor in Windows, you can use the standard Notepad application.

The HTML code of the page is placed inside the container . Without these tags, the browser is unable to determine the document format and interpret it correctly. A web page is divided into two logical parts: header and content.

The header of a web page is contained in a container and contains help information about the page that is not displayed by the browser, as well as the title of the document.

The title of the web page is contained in the container and is displayed in the title bar of the browser. Let's call our Web page UComputerF:

<Т1ТLЕ>Computer

Let's get acquainted - Computer

HTML tags are used to define various parameters text formatting. It is advisable to highlight the page title large print. The title font size is set by tags from<Н1>(largest) up to<Н6>(the smallest).

By default, text is aligned to the left edge of the page. However, the header is usually placed in the center of the page (in this case, the browser window). The ALIGN attribute of the title tag allows us to do this:

<Н1 ALIGN="center">

Web sites can contain images in three graphic formats - GIF, JPG and PNG. A tag is used to insert an image with the src="/kmh file" attribute:

Users sometimes, in order to save time, disable loading graphic images in the browser and read only texts. Therefore, in order not to lose the meaning and functionality of the page, an explanatory text should be displayed instead of a picture.

For this tag has one more ALT attribute, the meaning of which is the explanatory inscription:

As a result, we will get the HTML code of the Web page:

<Т1ТЬЕЖомпьютер

Let's get acquainted -

Computer

1. Folders and files (file type, file name). File system. Basic operations with files in the operating system

File. All programs and data are stored in the long-term (external) memory of the computer in the form of files. File - this is a certain amount of information (program or data) that has a name and is stored in long-term (external) memory.

The file name consists of two parts separated by a dot: the actual Name file and an extension that defines its type (program, data, etc.). The actual name of the file is given by the user, and the file type is usually set automatically by the program when it is created.

Different operating systems have different filename formats. In the MS-DOS operating system itself Name The file must contain no more than eight letters of the Latin alphabet and numbers, and the extension consists of three Latin letters, for example:

proba.txt

In the Windows operating system, the file name can have up to 255 characters, and the Russian alphabet can be used, for example:

Units of information.doc

File system. Each storage medium (floppy, hard or laser disk) can store a large number of files. The order in which files are stored on the disk is determined by the installed file system.

For disks with a small number of files (up to several dozen) it is convenient to use single-level file system, when a directory (disk table of contents) is a linear sequence of file names.

If hundreds and thousands of files are stored on the disk, then for ease of searching, the files are organized into multi-level hierarchical file system, which has a tree-like structure.

The initial, root, directory contains subdirectories of the 1st level, in turn, in each of them there are subdirectories of the 2nd level, etc. It should be noted that files can be stored in directories of all levels.

Operations on files. IN While working on files on a computer, the following operations are most often performed: copying(a copy of the file is placed in another directory); moving(the file itself is moved to another directory); deletion(the file entry is removed from the directory); renaming(file name changes).

Graphical representation of the file system. The MS-DOS hierarchical file system containing directories and files is represented in the Windows operating system through a graphical interface in the form of a hierarchical system of folders and documents. A folder in Windows is analogous to an MS-DOS directory.

However, the hierarchical structures of these systems are somewhat different. In the MS-DOS hierarchical file system, the top of the object hierarchy is the root directory of the disk, which can be compared to the trunk of a tree - branches (subdirectories) grow on it, and leaves (files) are located on the branches.

2. Logical addition. Truth table

In the algebra of logic, combining two (or more) statements using the conjunction UiliF is called logical addition operation or disjunction.

A compound statement formed as a result of logical addition (disjunction), true when at least one of the simple statements included in it is true.

The operation of logical addition (disjunction) is usually denoted either by the sign УвФ or by the addition sign У+Ф:

We have written down the formula for the logical addition function, the arguments of which are the logical variables A and B, taking the values ​​true (1) and false (0).

Logical addition function F can also take only two values: true (1) and false (0). The value of a logical function can be determined using the truth table of a given function, which shows what values ​​the logical function takes for all possible sets of its arguments (Table 3).

Using a truth table, it is easy to determine the truth of a compound statement formed using the operation of logical addition. Review;

rome, for example, compound statement U2 x 2 = ° 4 or 3 x 3 = 10F. First simple statement true (A= 1), and the second statement false (B= 0); Using the table, we determine that the logical function takes the value true (F = 1), i.e. this composite

statement true.

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1. Legal protection of computer programs and databases was first fully introduced in the Russian Federation by the Law on the Legal Protection of Programs for Electronic Computers and Databases F, which came into force on October 20, 1992. The legal protection provided by this law applies to all types of computer programs (including operating systems and software systems), which can be expressed in any language and in any form. To recognize and exercise copyright in a computer program, its registration with any organization is not required. Copyright in a computer program arises automatically when it is created. To notify of his rights, the program developer may, starting from the first release of the program, use a copyright symbol consisting of three elements:

The letters C in a circle or parentheses;

Name (name) of the copyright holder;

Data protection.Protection against illegal copying and use. Software protection to prevent copying of distribution diskettes may consist of using non-standard formatting. In addition, an encrypted program key can be placed on a floppy disk or CD-ROM, without which the program becomes unusable and is lost when copied. Hardware protection against illegal use can be implemented using a hardware key, which is usually connected to the parallel port of the computer. Protecting access to your computer. Passwords are used to protect against unauthorized access to data stored on a computer. The computer allows access to its resources only to those users who are registered and have entered the correct password. Each specific user may be allowed access only to certain information resources. In this case, it is possible to register all unauthorized access attempts. Protect disks, folders and files. Each disk, folder and file can be protected from unauthorized access: for example, by setting certain access rights (full or read only), and different for different users. Protecting information on the Internet. Servers on the Internet host various important information: Web sites, files, etc. If a computer is connected to the Internet, then, in principle, any user also connected to the Internet can access the information resources of this server. He is able to change or replace the site's Web page, erase or, conversely, write a file, etc. To prevent this from happening, access to the server's information resources (its administration) is carried out using a password. If the server has a connection to the Internet and simultaneously serves as a local network server (Intranet server), then unauthorized penetration from the Internet into the local network is possible. To avoid this, a software or hardware barrier is installed between the Internet and the Intranet using a firewall. The firewall monitors data transfer between networks and prevents unauthorized access.

2 . Basic logical devices of a computer (adder, register)

Since any logical operation can be represented as a combination of three basic operations (AND, OR, NOT), any computer devices that process or store information can be assembled from basic logical elements like bricks.

Logic element I. To inputs L and IN of a logical element, four pairs of signals of different values ​​are sequentially supplied, the output is a sequence of four signals, the values ​​of which are determined in accordance with the truth table of the logical multiplication operation B(0,1,0,1) AND A(0,0,1,1) = F(0,0,0,1)

OR gate. To the entrances A And IN of a logical element, four pairs of signals of different values ​​are sequentially supplied, and the output is a sequence of four signals, the values ​​of which are determined in accordance with the truth table of the logical addition operation A(0,0,1,1) OR B(0,1,0,1) = F(0,1,1,1)

Logical element NOT. Two signals are sequentially applied to input A of the logical element; the output produces a sequence of two signals, the values ​​of which are determined in accordance with the truth table of logical negation (Fig. 13). A(0,1) NOT = F(1,0)

Adder. In order to simplify the computer's operation as much as possible, the entire variety of mathematical operations in the processor is reduced to the addition of binary numbers. Therefore, the main part of the processor is the adder, which provides such addition.

When adding binary numbers, a sum is formed in this digit, and it can be transferred to the most significant digit. Let us denote the terms (A, B), transfer (R) and sum (S). Let's build a table for adding single-digit binary numbers, taking into account the transfer to the most significant digit (Table 4). Components: carry amount

A = 0,0,1,1 P=0,0,0,1 S=0,1,1,0

From this table it is immediately clear that the carry is implemented using the logical multiplication operation: P=A&B. To determine the amount, we apply the following expression: S = (A v B)&(not (A&B))

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1. Let's look at the process of solving a problem using a specific example:

A body is thrown vertically upward with an initial speed from a certain height. Determine its location and speed at a given time. On the first stage is usually built descriptive information model object or process. In our case, an idealized model of object motion is created using physical concepts. From the conditions of the problem, the following basic assumptions can be formulated: 1) the body is small compared to the Earth, therefore it can be considered a material point; 2) the speed of throwing the body is small, therefore: - the acceleration of free fall is considered a constant value; - air resistance can be neglected. At the second stage is created formalized model, that is, the descriptive information model is written using some formal language. From the physics course it is known that the motion described above is uniformly accelerated. At a given initial speed (V0), initial height (But) and free fall accelerations (g- 9.8 m/s 2) speed dependence (V) and height (H) from time (t) can be described by the following math. Formulas:

V=Vo-g*t, Y=Ho+V*t – gt^2/2

At the third stage it is necessary to transform the formalized information model into computer model, that is, express it in a language understandable to a computer. There are two fundamentally different ways to build a computer model:

Creating an algorithm for solving a problem and coding it in one of the programming languages;

Formation of a computer model using one of the applications (spreadsheets, DBMS, etc.). To implement the first way, you need to build an algorithm for determining the coordinates of a body at a certain point in time and code it in one of the programming languages, for example, Visual Basic. The second path requires the creation of a computer model that can be examined in spreadsheets. To do this, you should present a mathematical model in the form of a table of the function of the dependence of the coordinate on time (function table N = But + V X t - ((g t 2)/2)) and tables of the dependence of body speed on time (V=Vo-g*t) Fourth stage information model research consists of conducting computer experiment. If a computer model exists in the form of a program in one of the programming languages, it needs to be executed and the results obtained. If a computer model is examined in an application such as a spreadsheet, you can sort or search the data, create a chart or graph, and so on. On the fifth stage is in progress analysis of the results obtained and if necessary adjustment of the studied model. For example, in our model it is necessary to take into account that there is no physical meaning in calculating the coordinates of a body after it falls on the Earth’s surface. Thus, technology for solving problems using a computer consists of the following stages: construction of a descriptive model - formalization - construction of a computer model - computer experiment - analysis of the results and adjustment of the model.

2. Each object has a large number of different properties. In the process of building a model, the main, most significant ones are identified. Thus, a model of an airplane must have a geometric similarity to the original, a model of an atom - correctly reflect physical interactions, the architectural layout of the city - landscape, etc.

Model - This is a new object that reflects the essential features of the object, phenomenon or process being studied. In different sciences, objects and processes are studied from different angles and different types of models are built. In physics, the processes of interaction and movement of objects are studied, in chemistry - their internal structure, in biology - the behavior of living organisms, etc. Let's take a person as an example; in different sciences it is studied within the framework of various models. In mechanics it can be considered as a material point, in chemistry- as an object consisting of various chemical substances, in biology - as a system striving for self-preservation, etc. On the other hand, different objects can be described by one model. Thus, in mechanics, various material bodies (from a planet to a grain of sand) are often considered as material points. The same object sometimes has many models, and different objects are described one model. All models can be divided into two large classes: models subject (material) I models symbolic (informational). Subject models reproduce the geometric, physical and other properties of objects in material form. The following models are widely used in the learning process: globe (geography), dummies (biology), models of crystal lattices (chemistry), etc. Information models represent objects and processes in the form of pictures, diagrams, drawings, tables, formulas, texts etc. The following models are often used at school: a drawing of a flower (botany), a map (geography), a formula (physics), a flowchart of an algorithm (computer science), D. I. Mendeleev’s periodic system of elements (chemistry), equation ( mathematics), etc.

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1. Natural languages ​​are used to create descriptive information models. Numerous descriptive information models are known in the history of science. For example, the heliocentric model of the world that Copernicus proposed was formulated as follows:

The Earth rotates on its axis and around the Sun;

All planets orbit around the Sun.

Formal languages ​​are used to build formal information models(mathematical, logical, etc.). The process of building information models using formal languages ​​is called formalization.

One of the most widely used formal languages ​​is mathematical. Models formed using mathematical concepts and formulas are called mathematical models. The language of mathematics is a collection of formal languages; You learned about some of them (algebraic, geometric) at school, and you can get acquainted with others during further studies.

The language of algebra allows one to formalize functional dependencies between quantities. Thus, Newton formalized the heliocentric system of the Copernican world, discovering the laws of mechanics and the law of universal gravitation and writing them down in the form of algebraic functional dependencies. In a school physics course, many different functional dependencies are considered, expressed in the language of algebra, which are mathematical models of the phenomena or processes being studied. The language of logic algebra (propositional algebra) makes it possible to construct formal logical models. WITH With the help of propositional algebra, simple and complex statements expressed in natural language are formalized (written in the form of logical expressions). By building logical models, it is possible to solve logical problems, create logical models of computer devices (adder, trigger), etc. In the process of understanding the world around us, humanity constantly resorts to modeling and formalization.

2. Multimedia technology allows you to simultaneously use different ways of presenting information: numbers, text, graphics, animation, video and sound.

An important feature of multimedia technology is its interactivity, i.e., the user is assigned an active role in the dialogue with the computer. The graphical interface of multimedia projects usually contains various control elements (buttons, text windows, etc.).

Recently, many multimedia software products have been created: - encyclopedias on history, art, geography, biology, etc.; - training programs in foreign languages, physics, chemistry, etc.

A multimedia computer, i.e. a computer that can work with multimedia data, must have a sound card for playback and synthesis of sound with connected speakers (headphones) and a microphone, and a CD-ROM drive that allows storing large-scale multimedia data. One of the multimedia applications is computer presentations. A computer presentation is a sequence of slides containing multimedia objects: numbers, text, graphics, animation, video and sound.

Publications on the World Wide Web are implemented in the form of multimedia Web sites, which, in addition to text, may include illustrations, animation, sound and video information.

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1. System consists of objects called elements systems. There are various connections and relationships between the elements of the system. For example, a computer is a system consisting of various devices, and the devices are interconnected both hardware (physically connected to each other) and functionally (information is exchanged between devices). An important feature of the system is its holistic functioning. The computer works normally as long as its main devices (processor, memory, motherboard, etc.) are in good working order. If you remove one of them, for example the processor, the computer will fail, that is, it will cease to exist as a system. Any system is located in space and time. The state of the system at each moment in time is characterized by its structure, i.e., the composition, properties of the elements, their relationships and connections with each other. Thus, the structure of the Solar system is characterized by the composition of the objects included in it (the Sun, planets, etc.), their properties (say, sizes) and interaction (gravitational forces). Models that describe the state of a system at a certain point in time are called static information models. In physics, for example, static information models describe simple mechanisms, in biology - the classification of the animal world, in chemistry- structure of molecules, etc. The state of systems changes over time, i.e. processes occur changes and development of systems. So, the planets move, their position relative to the Sun and each other changes; The Sun, like any other star, develops, its chemical composition, radiation, etc. changes. Models that describe the processes of change in the development of systems are called dynamic information models.IN in physics, dynamic information models describe the movement of bodies, in biology - the development of organisms or animal populations, in chemistry - the processes of passage chemical reactions, etc.

2. After declaring an array, a certain amount of memory space is allocated to store it. However, to start working with an array, you must first fill it, that is, assign certain values ​​to the array elements. Filling an array is done in various ways.

The first way is to have the array element values ​​entered by the user using the InputBox input function. For example, you can fill the string array strA(l) with letters of the Russian alphabet using the following program (event procedure) in Visual Basic:

Dim strA(l To 33) As String I As Byte

Sub Conraandl_Click()

For I = 1 To 33

strA(I) = InputBox("Enter a letter", "Fill_

array")

After launching the program and clicking the Command! letters of the alphabet should be placed on sequentially appearing input panels in the text field.

The second way to fill an array is to use the assignment operator. Let's fill the numeric array bytA (I) with random integers in the range from 1 to 100, using the random number function Rnd and the function for selecting the integer part of the number Int in a loop with a counter:

Dim bytA(l To 100), I As Byte

Sub Conimandl_CUck()

For I = 1 To 1.00

bytA(I) = Int(Rnd * 100)

Let's create a program to find the index of an array element whose value matches the given one. Let's take a character array containing the alphabet and determine the number of a given letter in alphabetical order. In the first cycle of the program, we will fill the string array with letters of the Russian alphabet. Then we enter the desired letter and in the second loop compare it with all the elements of the array. If there is a match, we will assign the variable N the value of the index of this element. Let's print the result.

Dim strAll To 33) As String I,N As Byte

Sub Commandl_Click() "fill array

For I = 1 Then 33

strA(I) = InputBox("Enter the next letter", __ "Fill the array")

"search for element

strB = InputBox ("Enter the letter you are looking for", "Search")

For I = 1 Then 33

If strB = strA(I) Then N = I

Formi. Print"Number of the element being searched"; strB; N

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1. Algorithm - this is an information model that describes the process of transforming an object from the initial state to the final state in the form of a sequence of commands understandable to the performer. Let's consider an information model that describes the process of editing text. First, must be defined initial state object and its final state(purpose of transformation). Therefore, for the text, you need to specify the initial sequence of characters and the final sequence, which must be obtained after editing. Secondly, in order to change the state of an object (the values ​​of its properties), certain actions (operations) must be performed on it. Performs these operations executor. The text editing executor can be a person, a computer, etc. Thirdly, the text conversion process must be divided into separate operations, recorded as separate instructions for the executor. Each performer has a certain set of system of commands understandable to the performer. In the process of editing text, various operations are possible: deleting, copying, moving or replacing its fragments. The text editor must be able to perform these operations. The division of the information process in an algorithm into separate commands is an important property of the algorithm and is called discreteness. In order for an executor to perform an object transformation according to an algorithm, he must be able to understand and execute each command. This property of the algorithm is called certainty(or accuracy). It is necessary that the algorithm ensures the transformation of an object from the initial state to the final state in a finite number of steps. This property of the algorithm is called finitude (or effectiveness). Algorithms can represent transformation processes for a wide variety of objects. Computational algorithms that describe the transformation of numerical data have become widespread. The word algorithm itself comes from algorithmi - Latin form of writing the name of an outstanding mathematician of the 9th century. al-Khwarizmi, who formulated the rules for performing arithmetic operations. The algorithm allows formalize execution of the information process. If the performer is a person, then he can perform the algorithm formally, without delving into the content of the task, but only strictly following the sequence of actions provided for by the algorithm.

2. operating system ensures the joint functioning of all computer devices and provides the user with access to its resources. The process of computer operation, in a certain sense, comes down to exchanging files between devices. The operating system has software modules that manage the file system. The operating system includes a special program - command processor, which asks the user for commands and executes them. The user can give, for example, a command to perform some operation on files (copying, deleting, renaming), a command to print a document, etc. The operating system must execute these commands. Various devices are connected to the computer backbone (disk drives, monitor, keyboard, mouse, printer, etc.). The operating system includes device drivers - special programs that provide control of the operation of devices and coordination of information exchange with other devices. Each device has its own driver.

To simplify the user's work, modern operating systems, and in particular Windows, include software modules that create a graphical user interface. In GUI operating systems, the user can enter commands using the mouse, whereas in command line mode, commands must be entered using the keyboard. The operating system also contains service programs, or utilities. Such programs allow you to maintain disks (check, compress, defragment, etc.), perform operations with files (archive, etc.), work in computer networks, etc. For user convenience, the operating system usually has And reference system. It is designed to quickly obtain the necessary information about the functioning of both the operating system as a whole and the operation of its individual modules. Operating system files are stored in external, long-term memory (hard disk, floppy disk, or laser disk). However, programs can only run if they are in RAM, so operating system files must be loaded into RAM. The disk (hard, floppy or laser) on which the operating system files are located and from which it is loaded is called systemic. After turning on the computer, the operating system is loaded from the system disk into RAM. If there are no system disks in the computer, a message appears on the monitor screen Non system disk and the computer freezes, i.e. e. loading of the operating system stops and the computer remains inoperative.

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1. Unlike linear algorithms, in which instructions are executed sequentially one after another, in algorithmic structures branching included condition, depending on the truth of the condition, one or another sequence of commands (series) is executed. We will call condition a statement that can be either true or false. A condition written in formal language is called conditional or logical expression. Conditional expressions can be simple And complex. A simple condition involves two numbers, two variables or two arithmetic expressions, which are compared with each other through comparison operations (equal to, greater than, less than..). For example:

5>3 ,str A = UinformatikaF

A complex condition is a sequence of simple conditions united by signs of logical operations. For example: 5>3 And strА="computer science".

The algorithmic structure of branching can be written in various ways:

Graphically, using a block diagram;

• in a programming language, such as Visual Basic and VBA

After the first keyword It, a condition must be placed, after the second keyword Then, a sequence of commands (series 1) that must be executed if the condition evaluates to true. After the third keyword Bise there is a sequence of commands (series 2) that should be executed if the condition evaluates to lie. The conditional jump operator can be written as multiline or in one-line form. In multiline form, it is written using an If statement. . . Then. . . Else. . . End If (If... To... Otherwise... End If). In this case, the second Then keyword is located on the same line as the condition, and the sequence of commands (series 1) is on the next one. The third keyword Else is on the third line, and the sequence of commands (series 2) is on the fourth. The end of the End If branch instruction is placed on the fifth line. In single-line form, this statement is written according to the If... Then... Else statement. If an instruction does not fit on one line, it can be split into multiple lines. This presentation of instructions is more visual for humans. The computer must know that an instruction divided into lines represents a single whole. This is provided by the hyphenation sign, which is specified by the underscore character after the space. The third keyword Else may not be present in the shortened form of the statement. (Optional parts of the statement are written in square brackets.) Then, if the condition is false, the execution of the conditional jump operator ends and the next line of the program is executed.

2. Presentation of information can be carried out using sign systems. Each sign system is built on the basis of a certain alphabet and rules for performing operations on signs. Sign systems are natural languages ​​(Russian, English, etc.), formal languages ​​(programming languages, number systems, etc.), biological alphabets (states of a neuron in the nervous system, nucleotides storing genetic information in a DNA molecule) and etc. Signs can have a different physical nature. For example, for writing, signs are used that are images on paper or other media; in oral speech, various sounds (phonemes) act as signs, and when processing text on a computer, signs are represented in the form of sequences of electrical impulses (computer codes). Coding, that is, the translation of information from one sign system to another is carried out using correspondence tables of sign systems, which establish a one-to-one correspondence between signs or groups of signs of two different sign systems. An example of such a table is the ASCII (American Standard Information Interchange Code) code table, which establishes a correspondence between international alphabet characters and their numeric computer codes. When storing and transmitting information using technical devices, it is advisable to abstract from the content of the information and consider it as a sequence of characters (letters, numbers, color codes of image dots, etc.). Based on the probabilistic approach to determining the amount of information, a set of symbols of a sign system (alphabet) can be considered as various possible states (events). Then, if we assume that the appearance of symbols in a message is equally probable, using the formula we can calculate how much information each symbol carries: N = 2 1 , Where N- number of characters in the alphabet, I - amount of information. The information capacity of signs depends on their number in the alphabet (the power of the alphabet): the greater their number, the greater the amount of information one sign carries. Thus, the information capacity of a letter in the Russian alphabet, if you do not use the letter УеФ, is:

32 = 2 1 , i.e. I = 5 bits

According to the alphabetical approach amount of information^ which contains a message encoded using a sign system is equal to the amount of information carried by one sign multiplied by the number of characters in the message.