Sections: Informatics
Purpose of the lesson. Introduce students to ways of representing and organizing texts in computer memory.
Questions studied:
- Advantages of file storage of texts.
- Coding of texts.
- Encoding table, international standard ASCII.
Lesson progress
I.Organizational moment
II. Explanation of new material
A computer can work with four types of information: text, graphic, numeric and sound. One of the most widespread applications of computers is working with texts: creating text documents and storing them on magnetic media in the form of files.
Why has working with test information on computers become so widespread?
Why in a very short period of time (10-15 years) in almost all enterprises and organizations, including our school, were typewriters replaced by computers?
To answer these questions, let’s consider the differences between processing and storing texts when writing manually and when creating texts on a computer.
Advantages of file storage of texts:
- saving paper;
- compact placement;
- the ability to reuse magnetic media for storing different documents;
- the ability to quickly copy to other magnetic media;
- the ability to transmit text over computer communication lines.
The most striking difference between computer text and paper text is that the information in it is organized according to the hypertext principle. Hypertext is a way of organizing text information within which semantic connections (hyperconnections) are established between its various fragments. You have already encountered hypertext when working with the Windows help system.
Sometimes it happens that a text consisting of letters of the Russian alphabet received from another computer cannot be read - some kind of “abracadabra” is visible on the monitor screen.
Guys, why do you think this is happening?
You don't have a definitive answer yet. At the end of the lesson we will try to answer this question again.
From a computer's point of view, text is any sequence of characters from the computer alphabet. It is not at all necessary that it be a text in one of the natural languages (Russian, English, etc.). These can be mathematical or chemical formulas, phone numbers, numerical tables. The most important thing is that all the characters used are included in the computer alphabet.
Enable slide Computer alphabet presentation Coding texts
To represent information in a computer, an alphabet with a capacity of 256 characters is used.
What is the information weight of one character of such an alphabet?
Let us recall the formula connecting the information weight of an alphabet symbol and the power of the alphabet: 2i = N
If the alphabet power is 256, then i = 8, and therefore one character carries 8 bits of information.
Any information is represented in the computer memory in binary, which means that each character is represented by 8-bit binary code.
8 bits = 1 byte, so the binary code for each character in computer text takes up 1 byte of memory.
The convenience of byte-by-byte character encoding is obvious because a byte is the smallest addressable part of memory and, therefore, the processor can access each character separately when processing text. On the other hand, 256 characters is quite a sufficient number to represent a wide variety of symbolic information.
Now the question arises, which eight-bit binary code to assign to each character. It is clear that this is a conditional matter; you can come up with many encoding methods.
All characters of the computer alphabet are numbered from 0 to 255. Each number corresponds to an eight-bit binary code from 00000000 to 11111111. This code is simply the serial number of the character in binary system Reckoning.
A table in which all characters of the computer alphabet are assigned serial numbers is called an encoding table.
The ASCII table (read asci) (American Standard Code for Information Interchange) has become the international standard for PCs. In practice, you can come across another table - KOI-8 (Information Exchange Code), which is used in global computer networks.
Let's look at the ASCII code table (textbook, p. 75).
Enable slide Encoding presentation characters Encoding texts
The ASCII code table is divided into two parts.
Only the first half of the table is the international standard, i.e. characters with numbers from 0 (00000000), to 127 (01111111). This includes lowercase and uppercase letters of the Latin alphabet, decimal numbers, punctuation marks, all kinds of brackets, commercial and other symbols.
Symbols with numbers from 0 to 31 are usually called control symbols. Their function is to control the process of displaying text on the screen or printing, feeding sound signal, text markup, etc.
Character 32 is a space, i.e. empty position in the text. All others are reflected by certain signs.
Please note that in the encoding table, letters (uppercase and lowercase) are arranged in alphabetical order, and numbers are ordered in ascending order. This observance of lexicographic order in the arrangement of symbols is called the principle of sequential coding of the alphabet.
The second half of the ASCII code table, called the code page (128 codes, starting from 10000000 and ending with 11111111), can have different options, each option has its own number.
The code page is primarily used to accommodate national alphabets other than Latin. In Russian national encodings, characters from the Russian alphabet are placed in this part of the table. For letters of the Russian alphabet, the principle of sequential coding is also observed.
Unfortunately, there are currently five different Cyrillic encodings (KOI8-R, Windows. MS-DOS, Macintosh and ISO). Because of this, problems often arise with transferring Russian text from one computer to another, from one software system to another.
Chronologically, one of the first standards for encoding Russian letters on computers was KOI8 ("Information Exchange Code, 8-bit"). This encoding was used back in the 70s on computers of the ES computer series, and from the mid-80s it began to be used in the first Russified versions operating system UNIX.
From the early 90s, the time of dominance of the MS DOS operating system, the CP866 encoding remains ("CP" means "Code Page", "code page").
Apple computers running operating systems Mac systems OS, use their own Mac encoding.
In addition, the International Standards Organization (ISO) has approved another encoding called ISO 8859-5 as a standard for the Russian language.
The most common encoding currently used is Microsoft Windows, abbreviated CP1251.
Since the late 90s, the problem of standardizing character encoding has been solved by the introduction of a new international standard called Unicode. This is a 16-bit encoding, i.e. it allocates 2 bytes of memory for each character. Of course, this increases the amount of memory occupied by 2 times. But such a code table allows the inclusion of up to 65536 characters. The complete specification of the Unicode standard includes all the existing, extinct and artificially created alphabets of the world, as well as many mathematical, musical, chemical and other symbols.
Guys, what questions will you have on the topic of the lesson?
Now let's try again to answer the question that was asked at the beginning of the lesson:
Why do we sometimes see text consisting of letters of the Russian alphabet, received from another computer, on our computer in the form of “abracadabra”?
Expected answer. Computers use different character encodings for the Russian language.
Now we will solve some examples.
Example 1. How many bits of computer memory does the word MICROPROCESSOR occupy?
Before we start solving the example, let’s remember how much memory one character of computer text takes up.
Expected answer. 1 byte
Solution. The word consists of 14 letters. Each letter is a symbol of the computer alphabet and therefore takes up 1 byte of memory. The word will take 14 bytes = 112 bits of memory, because 1 byte = 8 bits.
What is the principle of sequential alphabet coding?
Expected answer. In the encoding table, letters (uppercase and lowercase) are arranged in alphabetical order, and numbers are ordered in ascending order of value
Knowing the principle of sequential encoding allows us to solve some problems without resorting to a character encoding table.
Example 2. What is encrypted with the sequence of decimal codes: 108 105 110 107, if the letter i in the character encoding table has a decimal code of 105?
Solution. Let's remember the order of letters in the Latin alphabet - ... i, j, k, l, m, n, o .... The letter j will have code 106, k - code 107, etc. Therefore, the word link is encoded.
What does the term "code page" mean?
Expected response. This is the name of the second half of the ASCII code table, intended to accommodate national alphabets other than Latin.
Is the principle of sequential encoding observed in code pages?
Expected response. Complied with
Let's find out by solving the following example.
Example 3. The word bit is encrypted using the sequence of decimal codes: 225 232 242. Find the sequence of decimal codes of the same word, written in capital letters.
Solution. When solving, we take into account that the difference between the decimal code of a lowercase Cyrillic letter and the decimal code of the corresponding capital letter is 32. If the letter b corresponds to code 225, the capital letter B has the decimal code 225-32=193. Therefore, the word BIT corresponds to the sequence of codes: 193 200 210.
III. Independent practical work
(at the same time, students are called to solve examples at the board)
Example 4. Free volume RAM computer 640 KB. How many pages of a book will fit in it if the page has 16 lines of 64 characters per line?
Answer: (640?1024)/(16?64)=640 pp.
Example 5. The text occupies a full 10 sectors on a single-sided 180 KB floppy disk. The floppy disk is divided into 40 tracks of 9 sectors. How many characters does the text contain?
Answer: ((180?1024)/(40?9))?10=5120 characters.
IV. Summing up the lesson
Testing in the "Text editors" section
The character encoding table establishes the correspondence between
1) symbols, their decimal numbers and binary codes
2) symbols of different alphabets
3) characters and the number of bytes they occupy
4) symbols and numbers of memory cells that they occupy
5) symbols and keys
What will change when a character is presented on the monitor screen in different encodings (Windows, MS-DOS, KOI8-R, etc.)?
1) font typeface
2) character size
4) character outline
5) there will be no changes
The code (number) of the letter "j" in the character encoding table is 106. What sequence of letters will correspond to the word "file"?
Alphabet of Latin letters: abcdefghijklmn ...
1) 110 107 104 111
3) 132 112 90 140
4) 102 105 108 101
5) 90 102 114 86
The code sequence 105 162 109 of the encoding table encrypts some characters. Insert the correct statement in place of the ellipsis.
"Among these symbols..."
1) there cannot be letters of the Russian alphabet
2) there cannot be letters of the Latin alphabet
3) there may be letters of the Russian and Latin alphabets
4) there cannot be letters of the Russian and Latin alphabets
5) there can only be one letter of the Latin alphabet
To store text, 10 KB is required. How many pages will this text take if the page contains 40 lines of 64 characters per line?
Text editor cursor coordinates are fixed
1) in the text editor menu
2) in the dictionary of a text editor
3) in the status bar of the text editor
4) in a text editor window
5) in the copy buffer
Select a phrase whose spelling corresponds to the rules of typing on a computer:
1) All trams have ice windows. White trees, roofs, wires
2) I am a bright image in my heart: near the winter Volga, Yaroslavl is in the snow.
3) All trams have ice windows. White trees, roofs, wires.
4) I am a bright image in my heart on the shore: Yaroslavl is covered in snow near the winter Volga.
5) All trams have windows made of ice. The trees, roofs, and wires are white.
Select an action related to text formatting:
1) copying text fragments
2) correction of typos
3) spell check
4) changing the size of the fields
5) moving text fragments
When printing a document, 60 lines of 80 characters each fit on a page. What settings need to be changed to fit fewer characters on the page?
1) change the encoding
2) change the font style
3) reduce the size of page margins
4) reduce the font size
5) increase the spacing between lines
Which characters can be encrypted with ASCII table codes: 119 and 251?
IN text editor You can use only one font and two buttons to set effects such as bold and italic. How many different character styles can you get?
The size of the text editor window is 20 lines of 64 characters per line. The cursor is located in the upper left corner of the screen and points to the character located in the 25th line and 5th position of the text. Which of the following symbols will be visible in the window?
1) standing in the 25th line and 70th position of the text
2) standing in the 35th line and 50th position of the text
3) standing in the 1st line and 1st position of the text
4) standing in the 46th line and 57th position of the text
5) standing in the 20th line and 5th position of the text
The minimum set of functions that a text editor must perform does not include:
1) saving files
3) text formatting
4) work with graphics
5) text editing
To edit incorrectly typed characters, use the following keys:
1) Backspace, Delete, Insert
2) Home, End, Insert
4) Backspace, Delete
The clipboard is:
1) RAM section
2) hard disk partition
3) part of the input device
4) ROM section
5) part of the output device
The text takes up 0.25 KB of computer memory. How many characters does the text contain?
While the text editor is running, the spelling dictionary
1) loaded into RAM as needed
2) loaded into external memory as needed
3) is permanently located in the input device
4) is permanently in ROM
5) is permanently located in the output device
To move a piece of text from one place in the document to another, you need to run the command(s):
1) Copy, Paste
2) Cut
5) Paste
The text consists of 50 lines of 60 characters each. The size of the text editor window is 20 ´ 50 characters. The cursor is in the upper left corner of the working field and its position is displayed in the status bar: (11,11). How many characters will be visible on the screen?
How many words (from the point of view of a text editor) are contained in the following text, which contains a number of errors: “One, two, three, four, five. The bunny went out for a walk. You are running as a friend of the hunter.”
Literature
I. Semakin and others. Computer science. Basic course 7 – 9.
Previous 1 .. 113 > .. >> NextE) in the copy buffer.
2. While the text editor is running, the spelling dictionary:
A) loaded into external memory as needed;
B) is permanently located in the input device;
C) is permanently located in RAM;
Tests ^__________________________________________________________________________393
D) loaded into RAM as needed;
E) is constantly located in the output device.
3* The character encoding table establishes correspondence between:
A) symbols, their decimal numbers and binary codes;
B) symbols of different alphabets;
C) characters and the number of bytes they occupy;
D) symbols and numbers of memory cells that they occupy;
E) symbols and keys.
4, Graphics output devices include:
A) display;
B) mouse;
C) keyboard;
D) scanner;
E) graphic editor.
5- Text formatting includes the following:
A) copying text fragments;
B) correction of typos;
C) spell check;
D\ change paragraph indentations;
E) moving text fragments,
V. When you execute the following command(s), the selected text fragment goes to the clipboard:
A) insert;
B) replace;
C) check spelling;
D) align to the center;
E) cut and copy.
7. The text takes up 0.35 KB of computer memory. How many characters does the text contain?
394_______________________________________________Part a
A) 256;
B) 2048;
C) 32;
D) 250;
E) 2000.
&. The character numbers *2" and "B* in the ASCII encoding table are respectively equal:
A) 80 and 90;
B) 130 and 140;
C) 90 and 129;
D) 160 and 50;
E) 10 and 250;
9. Video memory page size - 125 KB. The graphic display works with a 16-color palette. What is the resolution of the graphic display?
A) 640x200;
B) 320*400;
C) 640x400;
D) 640x800;
E) 512x400.
10. To encode green color, use the code 010. How many colors does the palette contain?
A) 4; B) 3; C) 8; D) 16; E) 6.
11. The code (number) of the book in the character encoding table is 106. What sequence of codes will correspond to the word * file? Alphabet of Latin letters: abcdefghijklmnop,..
A) NO 107 104 111;
B) 74 98 120 66;
C) 132 112 90 140;
D) 102 105 10S 101;
E) 90 102 114 Y6.
12. The code sequence 105 162 109 of the encoding table encrypts some characters.
Among these symbols;
A) there cannot be letters of the Russian alphabet;
Tests_________________________r_______________________395
B) there cannot be letters of the Latin alphabet;
C) there may be letters of the Russian and Latin alphabets;
D) there cannot be letters of the Russian and Latvian alphabets;
E) there can be only one letter of the Latin alphabet*
1S. To store text, 84,000 bits are required. How many pages will this text take if the page contains 30 lines of up to 70 characters per line?
A) 40; B) 5; C) 50; D) 400; E) 350.
14. The video memory capacity is 62.5 KB. The graphic display operates in 640x400 pixel mode. What is the maximum number of colors a gallitra can contain?
A) 4; B) 2; C) 8; D) 16; E) 32.
15. To delete an incorrectly typed yen character, use the following key:
A) Ctrl;
B) Esc;
C) Num Lock;
D) Insert;
E)Delete-
16. The text editor window contains 25 lines with up to 60 characters per line. The graphic editor window operating in two-color mode is 80 x 25.
pixels. Compare the amount of memory required to store text that occupies the entire window of a text editor and to encode a picture that occupies the entire field of a graphics editor:
A) text requires more memory than a picture;
B) text requires less memory than a picture;
C) text requires as much memory as a picture;
396 Part 3
D) there is not enough information” to answer the question.
17. What characters can be encrypted with ASCII table codes 119 and 235?
A) “d*> and *sh*;
B) *j* and
C) and
D) and
Ej) fW^ and "s".
16. Part of the book is presented in color images in a 16-color format in the format 320x640 accurate* Pages containing text have a format of 64 lines of 48 characters per line* Determine the maximum possible number of pages that can be stored on a 40 MB hard drive, if the number of pages presented with color images is 80 more than the number of pages containing only text.
A) 400", B) 720; C) 320; D) 100; E) 530.
19. ^The contents of the video memory are continuously viewed and displayed... on the screen*. Instead of ellipses, you need to insert the words:
A) display processor, central processor;
B) central processor, display processor;
C) display processor, display processor;
D) central processor" graphics adapter;
B) graphics adapter, central processor,
20. In a text editor, you can use only one font and two buttons, which are used to set effects such as bold and italics. How many different character styles can you get?
Tests
397
A) 1; B) 2; C) 3; D)4; E) 6.
21. For 5 minutes at a speed of 10 bytes/sec, the leader of the Multi tribe transmitted an information Message. How many characters did it contain if the tribe's alphabet consists of 32 characters?
When using materials from this site - and placing a banner is MANDATORY!!!
The character encoding table establishes the correspondence between
1) symbols, their decimal numbers and binary codes
2) symbols of different alphabets
3) characters and the number of bytes they occupy
4) symbols and numbers of memory cells that they occupy
5) symbols and keys
What will change when a symbol is presented on the monitor screen in different
encodings (Windows, MS-DOS, KOI8-R, etc.)?
1) font typeface
2) character size
4) character outline
5) there will be no changes
The code (number) of the letter "j" in the character encoding table is 106.
What sequence of letters would correspond to the word "file"?
Alphabet of Latin letters: abcdefghijklmn ...
1) 110 107 104 111
3) 132 112 90 140
4) 102 105 108 101
5) 90 102 114 86
The code sequence 105 162 109 encoding table encrypts some
Insert the correct statement in place of the ellipsis.
"Among these symbols..."
1) there cannot be letters of the Russian alphabet
2) there cannot be letters of the Latin alphabet
3) there can be letters of the Russian and Latin alphabets
4) there cannot be letters of the Russian and Latin alphabets
5) there can only be one letter of the Latin alphabet
To store text, 10 KB is required.
How many pages will this text take?
if the page contains 40 lines of 64 characters per line?
Text editor cursor coordinates are fixed
1) in the text editor menu
2) in the dictionary of a text editor
3) in the status bar of the text editor
4) in a text editor window
5) in the copy buffer
Select a phrase whose spelling corresponds to the rules of typing on a computer:
1) All trams have ice windows. White trees, roofs, wires
2) I am a bright image in my heart: near the winter Volga, Yaroslavl is in the snow.
3) All trams have ice windows. White trees, roofs, wires.
4) I am a bright image in my heart on the shore: Yaroslavl is covered in snow near the winter Volga.
5) All trams have windows made of ice. The trees, roofs, and wires are white.
A08:Select an action related to text formatting:
1) copying text fragments
2) correction of typos
3) spell check
4) changing the size of the fields
5) moving text fragments
When printing a document, 60 lines of 80 characters each fit on a page. What settings need to be changed to fit fewer characters on the page?
1) change the encoding
2) change the font style
3) reduce the size of page margins
4) reduce the font size
5) increase the spacing between lines
Which characters can be encrypted with ASCII table codes: 119 and 251?
In a text editor, you can use only one font and two buttons to set effects such as bold and italic. How many different character styles can you get?
The size of the text editor window is 20 lines of 64 characters per line. The cursor is located in the upper left corner of the screen and points to the character located in the 25th line and 5th position of the text. Which of the following symbols will be visible in the window?
1) standing in the 25th line and 70th position of the text
2) standing in the 35th line and 50th position of the text
3) standing in the 1st line and 1st position of the text
4) standing in the 46th line and 57th position of the text
5) standing in the 20th line and 5th position of the text
The minimum set of functions that a text editor must perform does not include:
1) saving files
3) text formatting
4) work with graphics
5) text editing
To edit incorrectly typed characters, use the following keys:
1) Backspace, Delete, Insert
2) Home, End, Insert
4) Backspace, Delete
The clipboard is:
1) RAM section
2) hard disk partition
3) part of the input device
4) ROM section
5) part of the output device
The text takes up 0.25 KB of computer memory. How many characters does the text contain?
While the text editor is running, the spelling dictionary
1) loaded into RAM as needed
2) loaded into external memory as needed
3) is permanently located in the input device
4) is permanently in ROM
5) is permanently located in the output device
To move a piece of text from one place in the document to another, you need to run the command(s):
1) Copy, Paste
2) Cut
5) Paste
The text consists of 50 lines of 60 characters each. The size of the text editor window is 20 ´ 50 characters. The cursor is in the upper left corner of the working field and its position is displayed in the status bar: (11,11). How many characters will be visible on the screen?
How many words (from the point of view of a text editor) are contained in the following text containing a number of errors:
One, two, three, four, five. The bunny went out for a walk. A friend of the hunter you are running around.
