## 字幕表 動画を再生する

• Imagine trying to use words to describe every scene in a film,

• every note in your favorite song,

• or every street in your town.

• Now imagine trying to do it using only the numbers 1 and 0.

• Every time you use the Internet to watch a movie,

• listen to music,

• or check directions,

• that’s exactly what your device is doing,

• using the language of binary code.

• Computers use binary because it's a reliable way of storing data.

• For example, a computer's main memory is made of transistors

• that switch between either high or low voltage levels,

• such as 5 volts and 0 volts.

• Voltages sometimes oscillate, but since there are only two options,

• a value of 1 volt would still be read as "low."

• That reading is done by the computer’s processor,

• which uses the transistorsstates to control other computer devices

• according to software instructions.

• The genius of this system is that a given binary sequence

• doesn't have a pre-determined meaning on its own.

• Instead, each type of data is encoded in binary

• according to a separate set of rules.

• Let’s take numbers.

• In normal decimal notation,

• each digit is multiplied by 10 raised to the value of its position,

• starting from zero on the right.

• So 84 in decimal form is 4x10⁰ + 8x10¹.

• Binary number notation works similarly,

• but with each position based on 2 raised to some power.

• So 84 would be written as follows:

• Meanwhile, letters are interpreted based on standard rules like UTF-8,

• which assigns each character to a specific group of 8-digit binary strings.

• In this case, 01010100 corresponds to the letter T.

• So, how can you know whether a given instance of this sequence

• is supposed to mean T or 84?

• Well, you can’t from seeing the string alone

• just as you can’t tell what the sound "da" means from hearing it in isolation.

• You need context to tell whether you're hearing Russian, Spanish, or English.

• And you need similar context

• to tell whether youre looking at binary numbers or binary text.

• Binary code is also used for far more complex types of data.

• Each frame of this video, for instance,

• is made of hundreds of thousands of pixels.

• In color images,

• every pixel is represented by three binary sequences

• that correspond to the primary colors.

• Each sequence encodes a number

• that determines the intensity of that particular color.

• Then, a video driver program transmits this information

• to the millions of liquid crystals in your screen

• to make all the different hues you see now.

• The sound in this video is also stored in binary,

• with the help of a technique called pulse code modulation.

• Continuous sound waves are digitized

• by taking "snapshots" of their amplitudes every few milliseconds.

• These are recorded as numbers in the form of binary strings,

• with as many as 44,000 for every second of sound.

• the numbers determine how quickly the coils in your speakers should vibrate

• to create sounds of different frequencies.

• All of this requires billions and billions of bits.

• But that amount can be reduced through clever compression formats.

• For example, if a picture has 30 adjacent pixels of green space,

• they can be recorded as "30 green" instead of coding each pixel separately -

• a process known as run-length encoding.

• These compressed formats are themselves written in binary code.

• So is binary the end-all-be-all of computing?

• Not necessarily.

• There’s been research into ternary computers,

• with circuits in three possible states,

• and even quantum computers,

• whose circuits can be in multiple states simultaneously.

• But so far, none of these has provided

• as much physical stability for data storage and transmission.

• So for now, everything you see,

• hear,

• comes to you as the result of a simple "true" or "false" choice,

• made billions of times over.

Imagine trying to use words to describe every scene in a film,

B2 中上級

# バイナリコードは正確にはどのように動作しますか？- ホセ・アメリコ・N・L・F・デ・フレイタス (How exactly does binary code work? - José Américo N L F de Freitas)

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林宜悉 に公開 2021 年 01 月 14 日