Coding text information in a computer - sometimes an indispensable condition correct operation device or display of this or that fragment. How does this process occur during the computer's work with text and visual information, sound - we will analyze all this in this article.
Introduction
Electronic Calculating machine(which we are in Everyday life called a computer) perceives the text in a very specific way. For her, the encoding of textual information is very important, since she perceives each text fragment as a group of characters isolated from each other.
What are the symbols?
The role of symbols for the computer is not only Russian, English and other letters, but also punctuation marks, as well as other signs. Even the space with which we separate words when typing on a computer is perceived by the device as a symbol. Something very reminiscent of higher mathematics, because there, according to many professors, zero has a double meaning: it is a number, and at the same time does not mean anything. Even for philosophers, the question of a space in the text can become an actual problem. A joke, of course, but, as they say, in every joke there is some truth.
What is the information?
So, in order to perceive information, a computer needs to start processing processes. And what kind of information is there? The topic of this article is the encoding of textual information. We will pay special attention to this task, but we will also deal with other micro-topics.
Information can be textual, numerical, sound, graphic. The computer must start processes that provide encoding of textual information in order to display what we type on the keyboard, for example. We will see symbols and letters, this is understandable. But what does the car see? It perceives absolutely all information - and now we are talking not only about text - as a certain sequence of zeros and ones. They form the basis of the so-called binary code. Accordingly, the process that converts the information received by the device into an understandable one is called “binary coding of text information”.
Brief principle of the binary code
Why is the coding of information in binary code the most widespread in electronic machines? The text base, which is encoded using zeros and ones, can be absolutely any sequence of characters and signs. However, this is not the only advantage that binary text encoding of information has. The thing is that the principle on which this coding method is arranged is very simple, but at the same time quite functional. When there is an electrical impulse, it is labeled (conditionally, of course) by a unit. No impulse - mark zero. That is, text encoding of information is based on the principle of constructing a sequence of electrical impulses. A logical sequence composed of binary characters is called machine language. At the same time, coding and processing of textual information using a binary code makes it possible to carry out operations in a fairly short period of time.
Bits and bytes
The figure perceived by the machine contains a certain amount of information. It is equal to one bit. This applies to every one and every zero, which make up one or another sequence of encrypted information.
Accordingly, the amount of information in any case can be determined simply by knowing the number of characters in the binary code sequence. They will be numerically equal to each other. 2 digits in the code carry information of 2 bits, 10 digits - 10 bits, and so on. The principle of determining the information volume, which lies in a particular fragment of binary code, is quite simple, as you can see.
Encoding text information in a computer
Right now you are reading an article that consists of a sequence, as we believe, of the letters of the Russian alphabet. And the computer, as mentioned earlier, perceives all information (and in this case too) as a sequence not of letters, but of zeros and ones, denoting the absence and presence of an electrical impulse.
The thing is that one character that we see on the screen can be encoded using a conventional unit of measure called a byte. As written above, the binary code has a so-called information load. Recall that numerically it is equal to the total number of zeros and ones in the selected code fragment. So, 8 bits make 1 byte. In this case, the combinations of signals can be very different, as you can easily see by drawing a rectangle on paper, consisting of 8 cells of equal size.
It turns out that it is possible to encode textual information using an alphabet that has a capacity of 256 characters. What is the point? The meaning lies in the fact that each character will have its own binary code. Combinations that are “attached” to certain characters start from 00000000 and end at 11111111. If you move from binary to decimal system calculus, then you can encode information in such a system from 0 to 255.
Do not forget that now there are various tables that use the encoding of the letters of the Russian alphabet. These are, for example, ISO and KOI-8, Mac and CP in two variations: 1251 and 866. It is easy to make sure that the text encoded in one of these tables will not be displayed correctly in a different encoding. This is due to the fact that in different tables different characters correspond to the same binary code.
This was a problem at first. However, at present, special algorithms are already built into the programs that convert the text, bringing it to the correct form. 1997 was marked by the creation of an encoding called Unicode. In it, each character has at its disposal 2 bytes at once. This allows you to encode text that has much large quantity characters. 256 and 65536: is there a difference?
Graphics encoding
Encoding textual and graphical information has some similarities. As you know, to display graphic information, a computer peripheral device called a “monitor” is used. Graphics now ( we are talking now about computer graphics) is widely used in various fields. Good, hardware capabilities personal computers allow you to solve fairly complex graphics problems.
Processing video information has become possible in recent years. But the text at the same time is much “lighter” than graphics, which, in principle, is understandable. Because of this, the final size of graphics files must be increased. It is possible to overcome such problems, knowing the essence in which graphic information is presented.
Let's first understand what groups this type of information is divided into. First, it's raster. Secondly, vector.
Raster images are quite similar to checkered paper. Each cell on such paper is painted over in one color or another. This principle is somewhat reminiscent of a mosaic. That is, it turns out that in raster graphics, the image is divided into separate elementary parts. They are called pixels. Translated into Russian, pixels mean “dots”. Logically, the pixels are ordered relative to the rows. The graphic grid consists of just a certain number of pixels. It is also called a raster. With these two definitions in mind, we can say that bitmap is nothing more than a set of pixels that are displayed on a rectangular grid.
Monitor raster and pixel size affect image quality. It will be the higher, the larger the raster of the monitor. Raster sizes are the screen resolution that every user has probably heard of. One of the most important features that computer screens have is resolution, not just resolution. It shows how many pixels are in one or another unit of length. The resolution of a monitor is usually measured in pixels per inch. The more pixels per unit length, the higher the quality will be, since the “graininess” is reduced.
Audio stream processing
Coding of text and sound information, like other types of coding, has some peculiarities. We will now focus on the last process: encoding audio information.
The presentation of an audio stream (as well as a single sound) can be done in two ways.
Analogue form of sound information presentation
In this case, the value can take really great amount different values. Moreover, these same values do not remain constant: they change very quickly, and this process is continuous.
Discrete Form of Sound Information Representation
If we talk about the discrete method, then in this case the value can take only a limited number of values. In this case, the change occurs in leaps and bounds. It is possible to encode discretely not only sound, but also graphic information. As for the analog form, by the way.
Analog audio information is stored on vinyl records, for example. But the CD is already discrete way presentation of sound information.
At the very beginning, we talked about the fact that a computer perceives all information in machine language. To do this, information is encoded in the form of a sequence of electrical impulses - zeros and ones. Audio encoding is no exception to this rule. To process sound on a computer, you first need to turn it into that same sequence. Only after that, operations can be performed on a stream or a single sound.
When the encoding process occurs, the stream is subjected to temporal sampling. The sound wave is continuous, it develops over small sections of time. In this case, the amplitude value is set for each specific interval separately.
Conclusion
So, what did we find out in the course of this article? Firstly, absolutely all information that is displayed on a computer monitor, before appearing there, is encoded. Secondly, this coding consists in translating information into machine language. Thirdly, machine language is nothing more than a sequence of electrical impulses - zeros and ones. Fourth, there are separate tables for encoding different characters. And, fifthly, it is possible to present graphic and sound information in analog and discrete form. Here, perhaps, are the main points that we have analyzed. One of the disciplines studying this area is computer science. Encoding of textual information and its basics are explained at school, since there is nothing complicated about it.
Text information consists of characters: letters, numbers, punctuation marks, etc. One byte is enough to store 256 different values, which allows you to place any of the alphanumeric characters in it. The first 128 characters (occupying the seven least significant bits) are standardized using ASCII (American Standard Code for Information Interchange). The essence of encoding is that each character is assigned a binary code from 00000000 to 11111111 or the corresponding decimal code from 0 to 255. Various code tables are used to encode Russian letters (KOI-8R, СР1251, CP10007, ISO-8859-5 ):
KOI8R- eight-bit standard for encoding letters of Cyrillic alphabets (for the UNIX operating system). Developers KOI8R placed the characters of the Russian alphabet at the top of the extended ASCII table in such a way that the positions of the Cyrillic characters correspond to their phonetic counterparts in the English alphabet at the bottom of the table. This means that from the text written in KOI8R, it turns out the text written in Latin characters. For example, the words "high house" take on the form "dom vysokiy";
СР1251– eight-bit coding standard used in OS Windows;
CP10007- eight-bit coding standard used in the Cyrillic alphabet of the Macintosh operating system (Apple computers);
ISO-8859-5 - an eight-bit code approved as a standard for encoding the Russian language.
Graphic information encoding
Graphical information can be presented in two forms: analog and discrete. Painting canvas created by the artist is analog representation example, and the image printed with a printer, consisting of individual (elements) dots of different colors, is discrete representation.
By splitting the graphic image (sampling), the graphic information is converted from analog to discrete form. In this case, coding is performed - assigning a specific value to each element of the graphic image in the form of a code. Creation and storage of graphic objects is possible in several forms - in the form vector, fractal or raster Images. separate subject considered 3D (three-dimensional) graphics, which combines vector and raster imaging methods.
Vector graphics used to represent such graphic images as pictures, drawings, diagrams.
They are formed from objects - a set of geometric primitives (points, lines, circles, rectangles), which are assigned some characteristics, for example, line thickness, fill color.
An image in vector format simplifies the editing process, since the image can be scaled, rotated, and deformed without loss. In this case, each transformation destroys the old image (or fragment), and a new one is built instead. This way of presentation is good for diagrams and business graphics. When encoding a vector image, it is not the image of the object that is stored, but the coordinates of the points, using which the program recreates the image each time.
Main disadvantage vector graphics is the impossibility of photographic quality images. In vector format, the image will always look like a drawing.
Raster graphics. Any picture can be divided into squares, thus obtaining raster - two-dimensional array squares. The squares themselves raster elements or pixels(picture "s element) - elements of the picture. The color of each pixel is encoded by a number, which allows you to specify the order of color numbers for describing the picture (from left to right or top to bottom). The number of each cell in which the pixel is stored is stored in memory.
Drawing in bitmap format
Each pixel is assigned values for brightness, color, and transparency, or a combination of these values. A bitmap image has a number of rows and columns. This storage method has its drawbacks: the larger amount of memory required to work with images.
The volume of a raster image is determined by multiplying the number of pixels by the information volume of one point, which depends on the number of possible colors. AT modern computers the following screen resolutions are mainly used: 640 by 480, 800 by 600, 1024 by 768 and 1280 by 1024 pixels. The brightness of each point and its coordinates can be expressed using integers, which allows the use of binary code in order to process graphic data.
In the simplest case (black and white image without grayscale), each point of the screen can have one of two states - “black” or “white”, that is, 1 bit is needed to store its state. Color images are formed in accordance with the binary color code of each point, stored in the video memory. Color images can have different color depths, which are given by the number of bits used to encode the color of a point. The most common color depths are 8, 16, 24, 32, 64 bits.
To encode color graphic images, an arbitrary color is divided into its components. The following coding systems are used:
HSB (H - hue, S - saturation, B - brightness),
RGB (Red- red, Green - green, blue- blue) and
CMYK ( C yan - cyan, Magenta - magenta, Yellow - yellow and Black - black).
The first system is suitable for human, the second - for computer processing, and the last one for printing houses. The use of these color systems is due to the fact that the luminous flux can be formed by radiations that are a combination of "pure" spectral colors: red, green, blue, or their derivatives.
fractal is an object whose individual elements inherit the properties of parent structures. Since a more detailed description of elements of a smaller scale occurs according to a simple algorithm, such an object can be described with just a few mathematical equations. Fractals allow you to describe images that require relatively little memory to represent in detail.
Drawing in fractal format
3D graphics (3D) operates with objects in three-dimensional space. Three-dimensional computer graphics is widely used in cinema, computer games, where all objects are represented as a set of surfaces or particles. All visual transformations in 3D graphics are controlled by operators having a matrix representation.
Audio encoding
Music, like any sound, is nothing more than sound vibrations, by registering which, it can be accurately reproduced. To represent the sound signal in the computer memory, it is necessary to represent the received acoustic vibrations in digital form, that is, to convert them into a sequence of zeros and ones. With the help of a microphone, the sound is converted into electrical vibrations, after which it is possible to measure the amplitude of the vibrations at regular intervals (several tens of thousands of times per second), using a special device - analog to digital converter (ADC). To reproduce sound, a digital signal must be converted to analog using digital-to-analogue converter (DAC). Both of these devices are built into sound card computer. The indicated sequence of transformations is shown in fig. 2.6..
Transformation of an analog signal into a digital one and vice versa
Each measurement of sound is recorded in binary. This process is called sampling (sampling), performed by the ADC.
sample (sample English sample) is the time interval between two measurements of the amplitude of an analog signal. In addition to a period of time, a sample is also called any sequence of digital data that is obtained by analog-to-digital conversion. An important parameter sampling is the frequency - the number of measurements of the amplitude of the analog signal per second. Audio sampling rate range from 8000 to 48000 measurements per second.
Graphical representation of the discretization process
Playback quality is affected sample rate and resolution(the size of the cell reserved for recording the amplitude value). For example, when writing music to CDs, 16-bit values and a sampling rate of 44032 Hz are used.
By ear, a person perceives sound waves having a frequency ranging from 16 Hz to 20 kHz (1 Hz - 1 oscillation per second).
In the Audio DVD format, the signal is measured 96,000 times in one second, i.e. a sampling frequency of 96 kHz is used. To save hard disk space in multimedia applications, lower frequencies are often used: 11, 22, 32 kHz. This leads to a decrease in the audible frequency range, which means that what is heard is distorted.
Lesson topic: « Encoding of textual information.
Item: Informatics and ICT.
Class: 9-10.
Keywords : informatics, text coding, information coding.
Literature, er.
1. Textbook Ugrinovich N.D. Informatics and ICT basic course Grade 9;
Equipment : computer class, programsMicrosoftofficePowerPoint, assignments for the lesson in in electronic format(see Attachment).
Lesson type : Exploring a new topic.
Forms of work : frontal, collective, individual.
Annotation: number of students class, subgroup.
The purpose of the lesson: Give an idea about the coding of textual information.
Tasks:
Formation of ideas about the coding of textual information;
Contribute to educationfeelingsacollectivism, skillIlisten to the answers of comrades;
Development of attention and logical thinking;
Development of interest in the study of computer programs.
During the classes:
Teacher's introductory storywith a presentation(on eqa presentation on the topic was presented earlier).
Since the 60s, computers have been increasingly used for processing text information, and at present most of the PCs in the world are occupied with processing text information.
256 characters are enough to represent textual information.
According to the formulaN=2
I
, 256=
2
8
therefore, to encode one character, the amount of information equal to 1 byte is used. (Particular attention should be paid to the formula).
Encoding is that each character is assigned a unique binary code from 00000000 to 11111111 (or a decimal code from 0 to 255).
It is important that the assignment of a specific code to a symbol is a matter of agreement, which is fixed by the code table.
For different types Computers use different encodings.
With the spreadIBMPCcoding table has become an international standardASCII ( American Standard Code for information Interchange ) – American standard code for information exchange.
Only the first half is standard in this table, i.e. characters with numbers from 0 (00000000) to 127 (0111111). This includes the letter of the Latin alphabet, numbers, punctuation marks, brackets and some other symbols.
The remaining 128 codes are used in different options. In Russian encodings, characters of the Russian alphabet are placed.
Currently, there are 5 different code tables for Russian letters (KOI8,СР1251 , СР866,Mac, ISO).
A new international standard has now become widespreadUnicode , which allocates two bytes per character. With it, you can encode 65536 (2 16 = 65536) different characters.
Numbers are encoded according to the ASCII standard in two cases - during input-output and when they occur in the text. If the numbers are involved in the calculations, then they are converted to another binary code.
Let's take a number57 .
When used in text, each digit will be represented by its own code in accordance with the ASCII table. In binary, this is 0011010100110111.
When used in calculations, the code of this number will be obtained according to the translation rules in binary system and get - 00111001.
Today, many people use to prepare letters, documents, articles, books, etc.computer text editors . Computer editors mostly workwith an alphabet of 256 characters .
In this case, it is easy to calculate the amount of information in the text. If1 character of the alphabet carries 1 byte of information , then you just need to count the number of characters; the resulting number will give the information volume of the text in bytes.
I= K× i, where
I- information volume of the message
K- number of characters in the text
i- informational weight of one character
2 i = N
N- alphabet power
Problem solving. The presentation is built on the principle "We decided with the teacher - we decided for ourselves."
Summarizing. Putting marks. Homework.
Lesson summary on the topic"Coding of text information"
Goals: Creation of conditions for studying the topic of coding textual information.
Tasks:
Educational: Contribute to the memorization of basic terminology, the formation of an idea of \u200b\u200bcoding textual information. Formation of the ability to work with text. Create conditions for expanding and deepening knowledge about the history of coding development. Contribute to the development of skills in word processor.
Educational: Raise interest in the subject being studied; taking care of your health and the health of those around you. Participate in the formation of positive communication "teacher-student", "student-student".
Developing: To promote the possession of concepts and their interpretation; development of the ability to analyze, highlight the main thing, generalize, subject-speech skills to speak, listen; to improve the ability of students to fill in the tables. To create conditions for the development of psychological characteristics in students: memory, thinking, attention.
During the classes.
1. Actualization of knowledge.
Music from the movie Sherlock Holmes. The teacher reads the story: “Heavy steps were heard on the stairs, and a minute later a tall, ruddy, clean-shaven gentleman entered us. He was about to sit down, when suddenly his eyes fell on a piece of paper with funny signs, which I had just examined and left on the table.
What do you think of this, Mr. Holmes? he exclaimed. - I was told that you are a big fan of all sorts of mysterious cases. I sent you this paper in advance so that you have time to study it before my arrival.
Hill lifted the paper, and the rays of the sun illuminated it. It was a leaf torn from notebook. The following marks were drawn on it in pencil:
^ 209 236 229 245 ^ - 253 242 238^ ^241 238 235 237 246 229^
Holmes examined the paper carefully.
This case promises a lot of curious and extraordinary things,” he said.
Hello. Today we have a lesson in the knowledge of secrets. You will meet me as a computer science teacher at school No. 12, my name is Alla Vladimirovna, I am with you. And I hope that the knowledge of these secrets will be pleasant for all of us. In order for our lesson to bring us only positive emotions, let's agree that we will communicate using the rule of a raised hand.
What do you think we will talk about in class? What is the topic of our lesson? Encoding or encryption of what?
The teacher listens to the options and summarizes the answers received and reports the topic of the lesson - “Coding of textual information”.
Why do you think we study this topic in computer science class? Where and why is information encoding used?
What would you like to know about text encoding?
Where do you think we should start the lesson?
Do you know what coding, textual information is?
Plan: 1. Definition of concepts.
2. History of coding development.
3. Encodings or how texts are encoded now.
2. Primary development of the material.
In order for us to understand each other in the lesson today and speak the same language with you, we must get acquainted with the basic concepts of this topic. You have a folder with worksheets on your desks, now you need sheet number 1. On it you see a glossary with terms, I will give you 2 minutes to carefully familiarize yourself with these terms. Time has come, let's get to work.
Time to work has expired. Let's check how you learned these concepts. Words and their definitions are written on the board, please combine and get a terminological dictionary.
We are ready for the knowledge of secrets, and for this I propose to take a trip in a time machine.
The history of coding has about 4 thousand years. It can be conditionally divided into two periods, depending on which ciphers appeared.
Our time machine stopped in ancient Rome, where one of the earliest known ciphers was created, which bears the name of the Roman emperor Julius Caesar (1st century BC). Who knows the Caesar cipher?
Let me tell you about it: the essence of this cipher is as follows: each letter of the original alphabet is replaced by the third letter after it in the alphabet, which is considered to be written in a circle, i.e., after the letter “I”, the letter “A” follows. For example, let's encode the word "code" using the Caesar cipher; (The teacher on the interactive whiteboard moves the letters and the children help him in chorus).
Now I invite you to complete the task yourself. Let's translate the word "Vision" using the Caesar code. One person performs the task at the blackboard, others in worksheets No. 2.
And now let's decipher the word written using the Caesar cipher "NSPTYABKHZU". We carry out task number 2 in the worksheets.
Answer: Computer.
Why do you think I coded these particular words?
How does computer work affect human vision? Can this harmful effect be reduced? Maybe someone knows how?
Today in the lesson we will get acquainted with some ways to reduce this harmful effect. Here is the first way - it's exercises for the eyes.
Physical education:
1. Without turning your head, look “right - up - left - down”, and then we will perform this exercise into the distance counting from 1 to 6. Do the same, but “left - up - right - down” and look into the distance again.
2. Pick up a pencil or pen. Position the pencil at arm's length from the tip of your nose. Bring the pencil closer to the nose and follow it with your eyes and return it to its original position. Let's repeat 3 times.
3. Place your fingertips on your temples, squeezing them lightly. Blink quickly and lightly 10 times. Close your eyes and relax by taking 2-3 deep breaths in and out.
Our eyes rested and we continue our lesson, and in the meantime our time machine has stopped in the 19th century.
We are greeted by a strange sound. What do you think this sound means?
You're right, it's Morse code. It is with her invention that the second stage in the development of encoding textual information is associated. Samuel Finley Morse - American inventor and artist, he was called the "American Leonardo da Vinci"
The table with which Morse code is written is called the code table.
Look carefully at the Morse code code table. What symbols are used to encode letters in this table?
How many different characters are used in encoding?
What do you think this character encoding is called?
Such an encoding is called binary, i.e., an encoding that uses an alphabet of two characters "." and "-".
3. Awareness and comprehension of educational information.
Why do you think we settled on the binary encoding of textual information?
Our time machine tells us that it's time to return home to the 21st century. Indeed, textual information in modern computers is recorded using a binary code. Look at the screen, you probably didn’t realize that by pressing a letter on the keyboard, the computer, or rather the processor, encodes it in binary code, then recodes it back, and only after that you see the image of the letter on the monitor screen.
4. Primary consolidation of educational material.
Today we will get acquainted with one of the encodings that is used to encode textual information and, in particular, to encode the Russian alphabet. You have worksheet #3 on your desks. Take it, read the information and answer questions #3-5 on the worksheets.
Time to work is up, let's check what you got.
What is the name of the international character encoding table? (ASCII) What do these letters mean?
What are the two parts of this code table? (In the ASCII system, two coding tables are fixed - basic and extended. The base table fixes code values \u200b\u200bfrom 0 to 127, and the extended table refers to characters with numbers from 128 to 255).
Let's fill in the table:
Let's move on to working on the computer. I suggest you unravel the recipe for a vitamin salad. To do this, open the “Information Encoding” folder and the “Salad” document on the desktop of your computer.
On the sheet you see a salad bowl, in which instead of ingredients there are their codes written in ASCII encoding. Identify the ingredients of the salad by replacing the code with the appropriate picture.
To prevent the development of retinal dystrophy, each person's diet should contain foods that contain a large amount of beta-carotene, vitamin C, E, lutein, zinc and omega-3 fat. You can make a salad of peppers and beets - this dish is also very tasty, especially if you season it with olive oil or citrus juice. By the way, you can add carrots there.
5. Reflection (summarizing the lesson).
You remember that today we have a lesson in the knowledge of secrets. Have we solved all the mysteries today?
Let's go back to the beginning of the lesson.
We can unravel this mystery now. What encoding did you use for this?
“Laughter is the sun: it drives the winter from the human face” Victor Hugo. Now it is winter outside, recently there were very severe frosts, if you smile at each other, then any weather will be a joy to you.
What else do you think can be encoded? Have you ever used coding in your life? By means of writing SMS messages?
It turns out that in addition to the text, emotions can also be encoded. With the help of emoticons, which are depicted on the board.
To appreciate our collaboration, I suggest you code your mood: at the beginning of the lesson and at the end of the lesson. If the examples of emoticons from the presentation did not reflect your mood, you can come up with your own. Thank you for your cooperation.
6. Homework: come up with your own encoding of the Russian alphabet and present the encoding in the form of a code table.
Lesson #13
Lesson topic: "Coding of textual information".
Lesson Type: Educational.
Lesson Objectives:
To introduce students to the ways of encoding information in a computer;
Consider examples of problem solving;
To promote the development of cognitive interests of students.
Cultivate endurance and patience in work, a sense of camaraderie and mutual understanding.
Lesson objectives:
To form students' knowledge on the topic “Coding of text (character) information”;
To promote the formation of figurative thinking among schoolchildren;
Develop skills of analysis and introspection;
Develop the ability to plan your activities.
Equipment:
workplaces of students (personal computer),
teacher workplace,
interactive whiteboard,
multimedia projector,
multimedia presentation,
During the classes
I. Organizational moment.
On the interactive whiteboard, the first slide of a multimedia presentation with the topic of the lesson.
Teacher: Hello guys. Sit down. Duty officer, report the missing. (Report of the attendant). Thank you.
II. Work on the topic of the lesson.
1. Explanation of new material.
The explanation of the new material takes place in the form of a heuristic conversation with the simultaneous display of a multimedia presentation on an interactive whiteboard(Appendix 1).
Teacher: What kind of information encoding did we study in previous lessons?
Answer : Coding of graphic and multimedia information.
Teacher : Let's move on to the study of new material. Write down the topic of the lesson “Coding text information” (slide1). Issues under consideration (slide 2):
Historical excursion;
Binary encoding of textual information;
Calculation of the amount of text information.
Historical digression
Mankind has been using text encryption (encoding) since the very moment when the first secret information. Here are several text encoding techniques that were invented at various stages in the development of human thought (slide 3) :
Cryptography - this is cryptography, a system for changing letters in order to make the text incomprehensible to uninitiated persons;
Morse code or non-uniform telegraphic code, in which each letter or character is represented by its own combination of short elementary parcels electric current(dots) and elementary parcels of triple duration (dashes);
Sign language is a sign language used by people with hearing impairments.
Question : What other examples of encoding textual information can be given?
Students give examplesroad signs, electrical circuits, product barcode).
Teacher : (Show slidefour). One of the earliest known encryption methods bears the name of the Roman emperor Julius Caesar (1st century BC). This method is based on replacing each letter of the encrypted text with another, by shifting the alphabet from the original letter by a fixed number of characters, and the alphabet is read in a circle, that is, after the letter I considered a . So word bytes when shifted two characters to the right, it is encoded as a word GVLF . The reverse process of deciphering a given word is to replace each encrypted letter with the second one to the left of it.
(Slide Show 5) Decipher the phrase of the Persian poet Jalaluddin Rumi “kgnusm yoogkg fesl ttsfhya fzuzhschz fkhgrzh yoogxp”, encoded with a Caesar cipher. It is known that each letter of the source text is replaced by the third letter after it. As a support, use the letters of the Russian alphabet located on the slide.
Question : What did you get?
Students response:
Close your eyes let your heart become an eye
The answer is compared with the correct answer that appears on slide 5.
Binary coding of text information
Information expressed using natural and formal languages in writing, is calledtext information (slide 6).
How much information is needed to encode each character can be calculated by the formula: N = 2 I.
Question : Which of the following coding methods uses the binary principle of information coding?
Student answer: In Morse code.
Teacher : The computer also uses the principle of binary encoding of information. Only instead of a dot and a dash, 0 and 1 are used (slide 7) .
Traditionally, 1 byte of information is used to encode one character.
Question : How many different characters can be encoded? (remind that 1 byte=8 bits)
Students answer: N = 2 I = 2 8 = 256.
Teacher : Right. Is this enough to represent textual information, including uppercase and lowercase letters of the Russian and Latin alphabets, numbers and other symbols?
Children count the number of different symbols:
33 lowercase letters of the Russian alphabet + 33 uppercase letters = 66;
For the English alphabet 26 + 26 = 52;
Numbers from 0 to 9, etc.
Teacher: What is your conclusion?
Withdrawal of students : It turns out that 127 characters are needed. There are still 129 values left that can be used to indicate punctuation marks, arithmetic signs, service operations (line feed, space, etc.). Therefore, one byte is enough to encode the necessary characters for encoding textual information.
Teacher : In a computer, each character is encoded with a unique code.
An international agreement has been adopted to assign each character its own unique code. The ASCII code table (American Standard Code for Information Interchange) has been adopted as an international standard (slide 8).
This table contains codes from 0 to 127 (letters of the English alphabet, signs of mathematical operations, service symbols, etc.), and codes from 0 to 32 are assigned not to symbols, but function keys. Write down the name of this code table and the range of characters to be encoded.
Codes 128 to 255 are assigned to the national standards of each country. This is sufficient for most developed countries.
For Russia, several different code table standards have been introduced (codes 128 to 255).
Here are some of them (slide9-10). Consider and write down their names:
KOI8-R, SR1251, SR866, Mac, ISO.
Open the computer science workshop on pages 65-66 and read about these encoding tables.
Teacher : AT text editor MS Word, to display a character on the screen by its code number, you need to hold down the “ALT” key on the keyboard and type the character code on the additional numeric keypad (slide 11):
Concept of Unicode encoding
Decision : There are 108 characters in this phrase, including punctuation marks, quotation marks and spaces. We multiply this number by 8 bits. We get 108*8=864 bits.
Teacher : Consider problem number 2. (The condition is displayed on the interactive whiteboard).<Рисунок 3> Write down the condition: Laser printer Canon LBP prints at an average speed of 6.3 Kbps. How long will it take to print an 8-page document if it is known that there are an average of 45 lines on one page, 70 characters per line (1 character - 1 byte) (see Fig. 2).
Decision:
1) Find the amount of information contained on 1 page:
45 * 70 * 8 bits = 25200 bits
2) Find the amount of information on 8 pages:
25200 * 8 = 201600 bits
3) We bring to uniform units of measurement. To do this, we translate Kbits into bits:
6.3*1024=6451.2 bps
4) Find the print time: 201600: 6451.2 = 31.25 seconds.
III. Generalization
Teacher questions (slide 14):
1. What is the principle of encoding textual information used in a computer?
2. What is the name of the international character encoding table?
3. List the names of encoding tables for Russian characters.
4. In what number system are the codes in the encoding tables you listed?
We coded characters, sound and graphics. Can emotions be encoded?
Showing a slide 14.
IV. Summary of the lesson. Homework
§ 2.1, task 2.1, notes in notebooks.
