What Is Information Good?

Information refers to the objects that are transmitted and processed by audio, messaging, and communication systems, and refers generally to all the content that is transmitted by human society. People can recognize and transform the world by obtaining and identifying different information from nature and society to distinguish different things. Information is a form of universal connection in all communication and control systems. In 1948, the mathematician Shannon stated in a paper entitled "The Mathematical Theory of Communication": "Information is used to eliminate random uncertainties." The most basic unit for creating everything in the universe is information.

[xìn x]

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Don't worry, although the information is uncertain, there are ways to quantify it. According to the concept of information, people can conclude that information has the following characteristics:

1. The greater the probability P (x) of message x, the smaller the amount of information; conversely, the smaller the probability of occurrence, the greater the amount of information. It can be seen that the amount of information (we use I to represent) and the probability of message occurrence are inversely related.

2. When the probability is 1, 100% of what happened is known to everyone on earth, so the amount of information is 0.

3 When a message is composed of multiple independent small messages, the amount of information contained in this message should be equal to the sum of the information contained in each small message.

According to these characteristics, if it is represented by a mathematical logarithmic function, it can just represent the relationship between the amount of information and the probability of message occurrence: I = -log _a (P (x)). In this way, can the information be quantified? Now that the information can be quantified, must we give it a unit? A person's weight is measured in kilograms, and a person's height is measured in meters. So what unit of information should be measured? Usually the amount of information is measured in bits, which is more convenient, because the amount of information in a binary waveform is exactly equal to 1 bit.

Some classmates have a problem again: so to say that my family's Internet speed of 2Mbit / s, that is to say can transmit 2Mbit of information per second?

The bits here strictly do not refer to the amount of information, but to the signal. Originally, it can not be said that it is a signal of several bits, but because the amount of information of a binary waveform (symbol) is exactly equal to 1 bit, in engineering applications, a binary symbol is often called 1 bit, and the unit of information amount It became a signal unit. Although this is not rigorous, it is not contradictory. We pay attention to the conceptual distinction.

Some students still have questions: Suppose there is a message "Wolf is here", which is converted into a 100-bit data packet through source coding, then the amount of information is 100 bits. Then sent this 100bit to many people through the communication network, and many people received 100bit of information. However, some people think that the news of "the wolf is coming" is very important and a lot of information; but some people think it doesn't matter and the amount of information is very little. However, we know that the information content of this message is 100bit. Why is it different?

First of all, we just said that bits are a unit of information, but engineering is also used to use it as a unit of signal. The 100bit mentioned here refers to the signal. Secondly, the basic problem in communication is to regenerate information at one point, referring to the point-to-point situation. But even in the case of point-to-multipoint, since in actual communication systems, messages often refer to certain symbols sent. How much information these symbols can carry is related to the probability of occurrence of these symbols. For any receiving end, the probability of occurrence of these symbols is certain. It will not be said that this probability is for this receiver, and that it is for that receiver. That probability. For example, there is a string of symbols 221234. This string of symbols is composed of four symbols: 1, 2, 3, and 4. Assuming that the four symbols appear with a probability of 1/4, then in this string of symbols, 2 appears 3 times, so 2 The amount of information carried is -3 × log ₂ (1/4) = 6bit. We need to understand that the symbols transmitted in communication systems are equivalent to the messages we are talking about now.

Basic explanation of information

1. [Information]: A signal purposefully marked on the input of a communication system or computer ... (such as a number on a telephone number)

2. [Message]: Sentences related to the message: I heard that the intellectualization of seeking advice, the husband must have the information, please quickly enter. -"Three Heroes and Five Righteousness" ^[1]

Information Citation Explanation

1. Audio message.

Poems by Li Zhong in the South Tang Dynasty, "Evening in the Spring with Nostalgic Love": "Dream cuts off the beautiful woman's message, sees the long road and leans against the platform." Song Chenliang's "Plum Blossom" poem: "If you want to pass the spring message, don't be afraid of the snow." Back: "Song Jiang was overjoyed and said," Only Xian Xian goes fast, and he will know the information on the tenth day. "Ba Jin's" Home "Trinity:" What happened to the second cousin? " Why didn't you even give me one? "

2. Modern science refers to the content contained in messages, instructions, data, symbols, etc. issued by things. Man can recognize and transform the world by obtaining and identifying different information from nature and society to distinguish different things. Information is a form of universal connection in all communication and control systems.

Chen Yuan's "Sociolinguistics" 4.1: "According to the concept of physics, information is just a sequence of signals arranged in a certain way. In social communication, this definition is not enough: information must also have a certain meaning, or that Information must be a carrier of meaning. "Science Pictorial" No. 1 of 1983: "The operation of the entire subway is controlled by a central electronic computer. The information it depends on comes from the stations installed on the station and the lines between stations. High sensitivity instrument. " ^[1]