Coding is ... Signed systems: encoding information

Coding information is an incredibly wide area of knowledge. Of course, it is directly related to the development of digital technology. In many modern educational institutions the most popular topic is the coding of information. Today we will study the main interpretations of this phenomenon in relation to various aspects of the work of computers. We will try to answer the question: "Is coding a process, a method, an instrument, or all these phenomena simultaneously?"

Zeros and Units

Almost any types of data that are displayed on the computer screen, anyway, are a binary code consisting of zeros and ones. This is the simplest, "low-level" method of information encryption, which allows a PC to process data. The binary code is universal: it is understood by all computers without exception (in fact, for this purpose it was created - in order to standardize the use of information in digital form).

The basic unit that binary coding uses is the bit (from the phrase "binary digit"). It is either 0 or 1. As a rule, bits are not used individually, but are combined into 8-digit sequences - bytes. In each of them, thus, up to 256 combinations of zeros and ones (2 in the 8th degree) can be contained. As a rule, not single bytes are used to write significant volumes of information, but larger scales - with prefixes "kilo", "mega", "giga", "ter", etc., each of which is 1000 times larger than the previous one .

Coding text

The most common type of digital data is text. How is it encoded? This is a fairly easy to explain process. A letter, punctuation mark, number or symbol can be encoded by one or more bytes, that is, the computer sees them as a unique sequence of zeros and ones, and then, in accordance with the embedded recognition algorithm, displays on the screen. There are two main world standards for "encryption" of computer text - ASCII and UNICODE.

In the ASCII system, each character is encoded with only one byte. That is, through this standard, you can "encrypt" up to 256 characters - which is more than enough to display the symbols of most of the world's alphabets. Of course, all the existing national alphabetic systems do not fit into this resource. Therefore, each alphabet has its own "subsystem" of encryption. There is a coding of information with the help of sign systems, adapted to national samples of writing. However, each of these systems, in turn, is an integral part of the global ASCII standard adopted at the international level.

Within the ASCII system, this very resource of 256 characters is divided into two parts. The first 128 are the symbols assigned to the English alphabet (letters from a to z), as well as numbers, basic punctuation marks and some other symbols. The second 128 bytes are reserved, in turn, under the national letter systems. This is the "subsystem" for the non-English alphabets - Russian, Hindi, Arabic, Japanese, Chinese and many others.

Each of them is presented as a separate encoding table. That is, it can happen (and, as a rule, it happens) so that the same bit sequence will be responsible for different letters and symbols in two separate "national" tables. Moreover, in connection with the specifics of the development of the IT-sphere in different countries, even they differ. For example, two coding systems are most common for the Russian language: Windows-1251 and KOI-8. The first appeared later (as well as the operating system, consonant with it), but now many IT specialists use it as a matter of priority. Therefore, the computer, so that it can be guaranteed to read the Russian text, should be able to correctly recognize both tables. But, as a rule, there are no problems with this (if the PC has a modern operating system).

Methods of encoding texts are constantly being improved. In addition to the "single-byte" ASCII system, capable of operating only 256 values for symbols, there is also a "two-byte" UNICODE system. It is easy to calculate that it allows the implementation of text encoding in an amount equal to 2 in the 16th degree, that is, 65 thousand 536. It, in turn, has the resources for simultaneously coding the practical all existing national alphabets of the world. The use of UNICODE is no less common than the use of the "classic" ASCII standard.

Encoding graphics

Above we determined how the texts are "encrypted" and how bytes are used. What about digital photos and pictures? It's also quite simple. Just as it happens with the text, the main role in the coding of computer graphics is played by all the same bytes.

The process of building digital images in general is similar to the mechanisms on which the TV works. On the TV screen, if you look closely, the picture consists of a set of individual points, which together form the figures recognized at a certain distance by the eye. The television matrix (or CRT projector) receives from the transmitter the horizontal and vertical coordinates of each of the points and gradually arranges the image. The computer principle of encoding graphics works exactly the same. "Encryption" of images bytes is based on specifying each of the screen points of the corresponding coordinates (as well as the color of each of them). It's easy to speak. Of course, graphic coding is a much more complicated process than the same textual.

The method of specifying the corresponding coordinates and color parameters for points is called "raster". Similarly, many file formats for computer graphics are called. The coordinates of each of the image points, as well as their color, are written in one or more bytes. What determines their number? Mainly from how many shades of color are to be "encrypted". One byte, as you know, is 256 values. If there are enough shades for building a picture, we will manage this resource. In particular, 256 shades of gray can appear at our disposal. And this will be enough to encode almost any black and white images. In turn, for color images of this resource will clearly not be enough: the human eye, as is known, is able to distinguish up to several tens of millions of colors. Therefore, you need a "stock" of not 256 values, but hundreds of thousands of times more. Why to encode points, not one byte is involved, but several: according to existing standards, they can be 16 (you can "encrypt" 65,536 colors) or 24 (16 million 777 thousand 216 shades).

Unlike text standards, the variety of which is comparable to the number of world languages, the graphics are much simpler. The most common file formats (such as JPEG, PNG, BMP, GIF, etc.) are recognized on most computers in general equally well.

There is nothing difficult to understand, according to what principles the coding of graphic information is carried out . 9 grade of any average Russian school, as a rule, includes a course in computer science, where similar technologies are disclosed in quite a very simple and understandable language. There are also specialized training programs for adults - they are organized by universities, lyceums, or also schools.

Therefore, a modern Russian person has a lot of knowledge about codes that are of practical importance in terms of computer graphics. And if you want to get acquainted with the basic knowledge yourself, you can acquire affordable teaching materials. These include, for example, the chapter "Encoding of graphic information (Grade 9, textbook" Informatics and ICT "under the authorship of Ugrinovich ND).

Encoding of sound data

The computer is used regularly to listen to music and other audio files. Just like in the case of text and graphics, any sound on the PC is all the same bytes. They, in turn, are "decrypted" by the audio card and other microcircuits and converted into audible sound. The principle here is approximately the same as in the case of gramophone plates. In them, as you know, each sound corresponds to a microscopic groove on the plastic, which is recognized by the reader, and then it is voiced. The computer looks like everything. Only the role of grooves is played by bytes, in the nature of which, like in the case of text and pictures, binary coding lies.

If in the case of computer images a single element is a dot, then when recording a sound, this is the so-called "countdown". In it, as a rule, two bytes are assigned, generating up to 65 thousand 536 sound micro-vibrations. However, unlike the way it is done in the construction of images, to improve the sound quality, it is not adding additional bytes (obviously, and so more than enough), but increasing the number of "counts". Although in some audio systems, bytes use a smaller and larger number. When audio coding is performed, the standard unit for measuring the "flux density" of bytes is one second. That is, micro-vibrations, encrypted with 8 thousand samples per second, will obviously be of lower quality than the sequence of sounds encoded by 44 thousand "counts".

International standardization of audio files, as well as in the case of graphics, is well developed. There are several typical formats of audio media - MP3, WAV, WMA, which are used all over the world.

Encoding video

A kind of "hybrid scheme", in which sound encryption is combined with the encoding of pictures, is used in computer video clips. Usually, movies and clips consist of two types of data - this is the sound itself and the accompanying video. How the first component is "encrypted", we described above. With the second a little more difficult. The principles here are different than the above-mentioned graphic coding. But thanks to the universality of the "concept" of bytes, the essence of the mechanisms is quite understandable and logical.

Let us recall how the film is arranged. It is nothing more than a sequence of individual frames (they are, as a rule, 24). In a similar way, computer video clips are constructed. Each frame is a picture. About how it is built using bytes, we defined above. In turn, in the video sequence there is a certain area of code, which allows to link individual frames with each other. A kind of digital film substitute. A separate unit of measurement of the video stream (similar to the points for pictures and samples for sound, as in the "film" format of movies and videos), it is considered to be a frame. The last in one second, according to accepted standards, can be 25 or 50.

As well as in the case of audio, there are common international standards for video files - MP4, 3GP, AVI. Manufacturers of movies and commercials are trying to produce media samples that are compatible with as many computers as possible. The specified file formats - among the most popular, they open almost on any modern PC.

Data Compression

Storage of computer data is carried out on various media - disks, flash drives, etc. As we said above, bytes are usually "overgrown" with "mega", "giga", "ter" prefixes, etc. In some cases The value of the encoded files is such that it is impossible to place them with the available resources on the disk. Then, various methods of data compression are used. They, in fact, also represent coding. This is another possible interpretation of the term.

There are two main mechanisms for data compression. On the first of them the sequence of bits is written in the "packed" form. That is, the computer can not read the contents of the files (reproduce it as text, picture or video), if it does not perform the "unpacking" procedure. A program that performs data compression in this way is called an archiver. The principle of its operation is quite simple. Archiving data as one of the most popular methods by which it is possible to encode information, informatics at the school level is studied without fail.

As we remember, the process of "encrypting" files in bytes is standardized. Let's take the ASCII standard. To, say, encrypt the word "hello", we need 6 bytes, based on the number of letters. That's the amount of space the file with this text will occupy on the disk. What happens if we write the word "hello" 100 times in a row? Nothing special - for this we need 600 bytes, respectively, the same amount of disk space. However, we can use the archiver, which will create a file in which a much smaller number of bytes will be "encrypted" the command, which looks something like this: "hello multiply by 100". Having counted the number of letters in this message, we come to the conclusion that we only need 19 bytes to write such a file. And the same amount of disk space. When "unpacking" the same archive file, "decryption" occurs, and the text acquires the original form with "100 greetings". Thus, using a special program that uses a special encoding mechanism, we can save a significant amount of space on the disk.

The above process is quite universal: no matter what sign systems are used, the encoding of information for compression is always possible through the archiving of data.

What is the second mechanism? To some extent, it is similar to what is used in archivers. But its principal difference is that the compressed file can be displayed by the computer without the "unpacking" procedure. How does this mechanism work?

As we remember, in the original form the word "hello" takes 6 bytes. However, we can go to the trick and write it like this: "prvt". There are 4 bytes. All that remains to be done is to "teach" the computer to add the letters that we removed during the file display. I must say that in practice, the "learning" process is not necessary to organize. The basic mechanisms for recognizing missing characters are laid down in most modern PC programs. That is, the bulk of the files that we deal with every day are somehow "encrypted" by this algorithm.

Of course, there are also "hybrid" information coding systems that allow data compression while simultaneously using both of the approaches described above. And they, most likely, will be even more effective from the point of view of economy of disk space, than everyone separately.

Of course, with the word "hello", we have outlined only the basic principles of the operation of data compression mechanisms. In reality they are much more complicated. Different systems of information coding can offer incredibly complex mechanisms for "compression" of files. However, we see, due to what it is possible to achieve economies of disk space, practically without resorting to degradation of the quality of information on the PC. Particularly important is the role of data compression when using pictures, audio and video - these types of data are more demanding on disk resources than others.

What other "codes" are there?

As we said at the very beginning, coding is a compound phenomenon. Having dealt with the basic principles of encoding digital data based on bytes, we can affect another area. It is associated with the use of computer codes in several other meanings. Here, by "code" we mean not a sequence of zeros and ones, but a collection of different letters and symbols (which, as we already know, are already made from 0 and 1), which has practical significance for the life of modern man.

Software code

At the heart of the work of any computer program is the code. It is written in a language that the computer understands. The PC, decrypting the code, executes certain commands. A distinctive feature of the computer program from another type of digital data is that the code contained in it is capable of "decrypting" itself (the user just needs to start this process).

Another feature of the programs is the relative flexibility of the code used. That is, a person can give the same tasks to a computer using a sufficiently large set of "phrases," and, if necessary, in another language.

Document markup code

Another practically significant area of application of the letter code is the creation and formatting of documents. Typically, a simple display of characters on the screen is not enough in terms of the practical importance of using the PC. In most cases, the text should be built using a font of a certain color and size, accompanied by additional elements (such as, for example, tables). All these parameters are set, as well as in the case of programs, in specific languages that the computer understands. The PC, recognizing the "commands", displays the documents exactly as the user wishes. In addition, texts can be formatted in the same way, just as it does with programs, using different sets of "phrases" and even in different languages.

However, there is a fundamental difference between the codes for documents and computer programs. It consists in the fact that the former are not capable of deciphering themselves. To open files with formatted texts, third-party programs are always required.

Encryption of data

Another interpretation of the term "code" for computers is the encryption of data. Above we used this word as a synonym for the term "coding", and this is permissible. In this case, by encryption we will understand a different kind of phenomenon. Namely, the coding of digital data in order to prohibit access to them from other people. The protection of computer files is a major area of activity in the IT field. This is actually a separate scientific discipline, it also includes school computer science. Encoding files to prevent unauthorized access is a task whose importance is presented to citizens of modern countries as early as childhood.

How are the mechanisms used to encrypt data? In principle, it is as simple and understandable as all the previous ones, considered by us. Coding is a process easily explained from the point of view of the basic principles of logic.

Suppose we need to send a message "Ivanov goes to Petrov" so that no one can read it. We trust to encrypt the message to the computer and see the result: "10-3-1-15-16-3-10-5-7-20-11-17-6-20-18-3-21". This code is, of course, very simple: each digit corresponds to the ordinal number of the letters of our phrase in the alphabet. "And" stands on the 10th place, "B" - on 3, "A" - on 1, etc. But modern computer coding systems can encrypt data so that it will be incredibly difficult to find a key to them.