ict

Section 2. INFORMATION AND INFORMATION PROCESSES

Topic 2.1. Information and information measurement

Approaches to the concept of information and the measurement of information. Information objects of various types. The versatility of discrete (digital) information presentation. Representation of information in a binary number system.

The word "information" comes from the Latin word informatio, which translated means information, clarification, familiarization.

The following approaches to the definition of information can be distinguished:

* traditional (ordinary) - used in computer science: Information - this is information, knowledge, messages about the state of affairs that a person perceives from the outside world with the help of the senses (sight, hearing, taste, smell, touch).

* probabilistic - used in information theory: Information - this is information about objects and phenomena of the environment, their parameters, properties and condition, which reduce the existing degree of uncertainty and incompleteness of knowledge about them.

For a person: Information is knowledge which he receives from various sources through the senses.

All information that a computer processes is represented by a binary code using two digits - 0 and 1. These two characters 0 and 1 are usually called bits (from the English binary digit - a binary sign)

Bit - the smallest unit of measurement of the amount of information...

Question: "How to measure information?" very difficult.

The answer to it depends on what is meant by information. But since information can be defined in different ways, the measurement methods can also be different.

In computer science, different approaches to measuring information are used:

A meaningful approach to measuring information...

A message that halves the uncertainty of a person's knowledge carries 1 bit of information for him.

The amount of information contained in the message, is determined by the Hartley formula:

where N is the number of equally probable events; I is the amount of information (bits) contained in the message about one of the events.

Alphabetical (technical) approach to measuring information - based on counting the number of characters in the message.

If we assume that all the symbols of the alphabet occur in the text with the same frequency, then the amount of information contained in the message is calculated by the formula:

 Ic - information volume of the message

 TO - Characters

 N - power of the alphabet (number of characters)

 i - information volume of 1 symbol

The advantage of the binary number system is the simplicity of the operations performed, the ability to automatically process information using two states of PC elements and the shift operation

Coding Is an operation of converting characters or groups of characters of one character system into characters or groups of characters of another character system.

Decoding - decoding of coded characters, conversion of a character code into its image

Binary encoding - coding information as 0 and 1

Methods for encoding and decoding information in a computer, first of all, depends on the type of information, namely, what should be encoded:

Ø  numbers

Ø  symbolic information (letters, numbers, signs)

Ø  graphic images

Ø  sound

Numbers are used to record information about the number of objects.

Numbers are written using special sign systems, which are called number systems. 100 → 11001002

Notation - a set of techniques and rules for writing numbers using a specific set of symbols.

All number systems are divided into two large groups:

The quantitative value of each digit of a number depends on where (position or digit) one or another digit is written.

0.7770

The quantitative value of the digit of a number does not depend on where (position or digit) this or that digit is written.

XIX

Coding - assigning each character a decimal code from 0 to 255 or the corresponding binary code from 00000000 to 11111111

Assigning a specific code to a character Is a matter of agreement, which is fixed in the code table.

As international standard the code was adopted ASCII table (American Standard Code for Information Interchange):

Codes 0 to 32 (first 33 codes) - operation codes (line feed, space entry, i.e. correspond to function keys);

Codes 33 to 127 - international, correspond to symbols of the Latin alphabet, numbers, signs of arithmetic operations, punctuation marks;

Codes 128 to 255- national, i.e. national alphabet encoding.

on the 1 character allotted 1 byte (8 bits), in total, 28 = 256 characters can be encoded

 Since 1997, a new international standard has appeared Unicodewhich takes one character to encode 2 bytes (16 bits), and 65536 different characters can be encoded (Unicode includes all existing, extinct and artificially created alphabets of the world, many mathematical, musical, chemical and other symbols)

Currently, there are five Cyrillic encodings: KOI-8, CP1251, CP866, ISO, Mac. To convert text documents from one encoding to another, there are programs calledConverters.

Graphic encoding

Spatial sampling - conversion of a graphic image from an analog form to a digital computer format by dividing the image into separate small fragments (dots) where each element is assigned a color code.

Pixel - min area of ​​the image on the screen, of a given color

Bitmapformed from separate points - pixels, each of which can have its own color. The binary code of the image displayed on the screen is stored in video memory. Raster graphics image coding resembles a mosaic of squares having a specific color

 Image encoding quality depends on:

1) the size of a point (the smaller its size, the greater the number of points in the image);

2) the number of colors (the larger the number of possible states of a point, the better the image is) Color palette - the set of colors used

 The quality of the bitmap depends on:

1) the resolution of the monitor - the number of dots vertically and horizontally.

2) used palette of colors (16, 256, 65536 colors)

3) color depth - the number of bits to encode the color of a point

1 bit is used to store a black and white image.

Color images are formed in accordance with the binary color code that is stored in the video memory. Color images have different color depths. The color image on the screen is formed by mixing the three basic colors - red, green and blue. Base colors can be set to different intensities for a rich palette.

In analog form, sound is a wave of continuously varying amplitude and frequency. They began to work with sound files on a computer in the early 90s. At the heart of audio coding using a PC is the process of converting air vibrations into electrical current fluctuations and the subsequent sampling of an analog electrical signal. The encoding and reproduction of sound information is carried out using special programs (sound editor). The quality of playback of the encoded sound depends on - the sampling frequency and its resolution (audio encoding depth - the number of levels)

Time sampling - a method of converting sound into digital form by breaking a sound wave into separate small time sections, where the amplitudes of these sections are quantized (they are assigned a certain value).

This is done using an analog-to-digital converter located on the sound card. Thus, the continuous dependence of the signal amplitude on time is replaced by a discrete sequence of loudness levels. Modern 16-bit sound cards encode 65536 different volume levels or 16-bit sound depth (each value of the sound amplitude is assigned a 16-bit code)

Audio encoding quality depends on:

1) audio coding depth - the number of audio levels

2) sampling rate - the number of changes in the signal level per unit of time (as a rule, for 1 sec).

N - number of different signal levels

i - audio coding depth

Information volume of audio information is equal to:

I = i * k * t

where i is the depth of sound (bit)

 K - broadcast frequency (sound quality) (Hz) (48 kHz - audio CD)

 t - playing time (sec)

Recently, the computer is increasingly used to work with video information. The simplest such job is watching movies and video clips. It should be clearly understood that the processing of video information requires a very high speed of the computer system.

            What is filmfrom a computer science point of view? First of all, it is a combination of sound and graphic information. In addition, to create a motion effect on the screen, an inherently discrete technology of fast change of static images is used. Studies have shown that if more than 10-12 frames are replaced in one second, then the human eye perceives the changes in them as continuous.