Binary Number System

The binary number system is a base-2 system that uses only two digits, 0 and 1. Each position represents a power of 2: from the right, the places are 1, 2, 4, 8, 16 and so on. For example, binary 1011 is 8 + 0 + 2 + 1 = 11 in decimal.

Computers use binary because electronic circuits have two stable states, on and off. All data, including numbers, text, images and instructions, is ultimately stored and processed as binary digits (bits). Hexadecimal (base 16) is often used as a shorter way to write binary values.

Decimal 13 to binary (divide by 2, read remainders upwards):
13 / 2 = 6 remainder 1
 6 / 2 = 3 remainder 0
 3 / 2 = 1 remainder 1
 1 / 2 = 0 remainder 1
=> 1101

Binary 1101 to decimal: 8 + 4 + 0 + 1 = 13