**Binary,** also known as the base-2 number system, is a way of writing numbers by using only two different symbols, usually a one (1) and a zero (0). Even though this is a whole eight symbols less than we normally use (this is called **decimal,** or the base-10 number system), it's still possible to write out each and every number.

While counting with only two symbols can seem pretty confusing for humans, binary makes a lot of sense when thinking about computers. In fact, binary is used in just about every computer on Earth and every time you've used one, you've seen binary in action.

To get an idea of how binary works, let's first take a closer look at the decimal system (remember, the decimal system, or base-10, is how we normally write numbers). What happens when we count from nine to ten?

English | Base-10 |
---|---|

Nine | 9 |

Ten | 10 |

Okay, so here's where things start getting cool. Binary works in exactly the same way! The only difference is, we only have one symbol before we "run out" and have to start using another digit. Let's try counting again, this time from zero to two, and in both decimal and binary.

English | Base-10 | Base-2 |
---|---|---|

Zero | 0 | 0 |

One | 1 | 1 |

Two | 2 | 10 |

### The usefulness of binary code was understood centuries before the invention of the first digital computer.

In 1689, Gottfried Leibniz wrote an article explaining the basics of the binary numeral system and some of its potential uses. Although the idea for a programmable computing device had been put forward by Charles Babbage in the early 18th century, it wasn't until 1941 with Konrad Zuse's invention of the Z3, the first programmable, digital computer, that binary was put to use in computers.

### Binary numbers are stored in computers as groups of bits.

**Bits**are the smallest unit of storage in a computer. The word comes from combining the two words*binary*and*digit*. In a computer, a bit can either be on or off, representing either the binary digits 1 or 0.To make longer binary numbers, several bits are needed. For example, the binary number 101 (5 in decimal) requires 3 bits. A

**byte**is made up of 8 bits. Sound familiar?