**Binary Number System**

The binary system uses a base of 2. There are 2 digits: 0 and 1. Binary is used in computers because each bit (**b**inary dig**it**) can have just one of two values. We usually represent those two values as 1 and 0, but it can also be thought of as true or false; on or off.

The binary number system is a place system. The right most place is the ones place. As we move from right to left, each place is 2 times the previous place.

Place: | 8 |
4 |
2 |
1 |

Digit: |
1 |
0 |
1 |
1 |

Value: |
1x8 |
0x4 |
1x2 |
1x1 |

The value of the binary number 10112 =1x8 + 0x4 + 1x2 + 1x1 = 8 + 4 + 2 = 1410.

*For practical purposes we just add together the value of each place that has a one in it.*

We read the binary number 1011 as "one zero one one." Do not say "one thousand eleven," those terms refer to the decimal system.

The place values can also be written as powers of 2. The two rows in the table below have the same values.

Place: | 8 |
4 |
2 |
1 |

Power: |
2 |
2 |
2 |
2 |