Basics

Binary Code Basics: Why Do Computers Only Use 0 and 1?

The underlying world of computers is extremely simple, consisting of only 0s and 1s. Discover the secrets of this digital foundation and why we use binary.

December 21, 2025

4 min read

By Binary Code Translator

#binary#basics#computer-science

Imagine you are trying to teach a robot that can only flip "switches" to write poetry, paint, or even run complex video games. Sounds like an impossible task, right?

But in fact, this is the magical phenomenon we see every day on computers, phones, and even smartwatches. The underlying world of computers is extremely simple, with only two "words": 0 and 1.

Today, let's uncover the underlying secrets of this digital world and see why smart humans chose this seemingly "clumsy" way to build digital civilization.

1. The Physical Truth: Computers are "Electrical Appliances"

To understand 0 and 1, you first need to understand the nature of a computer: it is not a thinking brain, but a pile of tiny circuit switches.

Inside a computer's CPU (Central Processing Unit), there are billions of microscopic components called Transistors.

The working principle of a transistor is very much like the light switch in your home:

On: Current flows, we denote this as 1.
Off: Current stops, we denote this as 0.

Why not use 0 to 9?

You might ask: "Since we can control voltage, why not divide the voltage into 10 parts to represent 0 to 9?"

Theoretically feasible, but reality is harsh. Electric current suffers from interference and loss during transmission.

If using 10 voltage levels: 0.5 volts represents 5, 0.6 volts represents 6. If the circuit fluctuates slightly and 0.5 volts becomes 0.55 volts, the computer gets confused: "Is this a 5 or a 6?", leading to data errors.
If using 2 voltage levels: Only "no power" and "full power". Even if the full power state loses a little bit due to interference, the computer can still firmly judge: "This is definitely powered, it's a 1!"

Conclusion: Binary is the most stable and fault-tolerant method.

2. The Magic of Translation: How do 0 and 1 become everything?

Since we only have 0 and 1, how do they turn into text, music, and complex video games? The answer is: Combination and Encoding.

Combinations of Numbers

Just as English has only 26 letters but can write the complete works of Shakespeare, different arrangements of 0 and 1 represent different meanings.

1 Bit: Can only represent 0 or 1 (two states).
8 Bits (1 Byte): Can produce 256 combinations.
For example: 01000001 in a common standard (ASCII) represents the uppercase letter A.

Multimedia Translation

Text: Every font and every character corresponds to a specific string of binary code in the computer's eyes.
Images: An image is made up of countless pixels. The color of each pixel is determined by the intensity of Red, Green, and Blue, and the intensity of each color is represented by a set of binary numbers.
Video: It's essentially playing dozens of images containing these binary data quickly within a second, plus audio data also converted from binary.

3. Decimal vs. Binary

In our daily lives, we use the Decimal system (base-10), because we have 10 fingers.

In the computer world, Binary (base-2) is used:

0 is 0
1 is 1
2 becomes 10 (because the position for 1 is full, we need to carry over)
3 becomes 11
4 becomes 100

This simple logical mathematics allows computers to perform addition, subtraction, multiplication, and division at incredibly fast speeds.

Summary

Computers only use 0 and 1 because:

Extremely Reliable: On physical hardware, judging "presence or absence" is much easier than judging "amount".
Extremely Simple: Simple rules mean fewer errors and higher processing efficiency.
Universal Combination: As long as there are enough permutations and combinations, 0 and 1 can simulate the entire universe.

Next time you tap your phone screen, imagine the billions of tiny switches behind it, frantically toggling 0s and 1s at speeds of billions of times per second. This is the cornerstone of modern technology.