There are several different number systems, each with a different base (sometimes called the radix). The base of a number system tells us how many different possible values a single digit can take. The number system we’re most used to is denary[1], which is base 10 (because it has ten possible values per digit: 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9). Binary is a base 2 number system, giving it two possible values per digit (0 and 1).
In denary, every digit has a value 10 times greater than the digit to its right:
To get the overall value, we simply multiply the value of the column by the value of the digit:
(9 x 100) + (4 x 10) + (2 x 1) = 941
Binary works using exactly the same principles, except every column is worth double the column to its right:
Every digit in binary is called a bit. To convert between binary and denary integers, we need to follow the relevant process.
[1] Another common term is decimal, which is also correct.