Bits vs Qubits
Classical Bits
The Language of Computers
At the heart of every computer, smartphone, and smart TV is a simple concept: the bit. Think of it as a light switch. It can only be in one of two states: on or off. There's no in-between. This fundamental on-or-off property is what makes a bit the smallest, most basic unit of information in all of classical computing.
Bit
noun
The basic unit of information in computing, representing a logical state with one of two possible values.
Computers don't see "on" and "off." Instead, they represent these two states with numbers: 1 for "on" and 0 for "off." This is called the binary system, and it's the language every traditional computer uses to process and store information. Everything you see on your screen—text, images, videos—is ultimately a massive collection of these 1s and 0s.
A single bit isn't very useful on its own, just as a single letter of the alphabet can't convey much. To represent more complex information, computers group bits together. A common grouping is a byte, which consists of eight bits.
With more bits, you can represent a wider range of values. This scales up exponentially.
| Number of Bits | Possible Combinations | Number of States |
|---|---|---|
| 1 | 0, 1 | 2 (or ) |
| 2 | 00, 01, 10, 11 | 4 (or ) |
| 3 | 000, 001, 010, ... | 8 (or ) |
| 8 (1 byte) | ... | 256 (or ) |
Using these combinations, computers can represent numbers, letters (like the letter 'A' which is 01000001 in one standard system), and even the color of a single pixel in a photo. Storing this information is one thing, but how do computers actually do anything with it?
Making Bits Work
Computers perform calculations by manipulating bits using tiny electronic circuits called logic gates. A logic gate takes one or more input bits and produces a single output bit based on a specific logical rule. By combining millions or billions of these simple gates, computers can perform incredibly complex tasks.
There are several types of logic gates, but they are all built from three fundamental operations: NOT, AND, and OR.
Let's look at each one.
The NOT gate is the simplest. It takes one input bit and flips it. A 1 becomes a 0, and a 0 becomes a 1. It's also called an inverter.
The AND gate is stricter. It takes two input bits and outputs a 1 only if both input A AND input B are 1. If either input is 0, the output is 0.
The OR gate is more lenient. It takes two input bits and outputs a 1 if input A OR input B (or both) are 1. It only outputs a 0 if both inputs are 0.
By linking these simple gates in complex arrangements, we get circuits that can perform arithmetic, process logic, and store data. A modern computer processor contains billions of these gates, all working together to run software and process information at incredible speeds.
From a single switch that can be on or off, we build a logical system capable of powering our digital world. This is the foundation upon which all classical computing is built.