Hexadecimal

A numeral system with a base of 16. Hexadecimal uses sixteen symbols: 0–9 (representing values zero to nine) and A-F (representing values ten to fifteen). For example:

 00, 01, 02, 03, 04, 05, 06, 07, 08, 09, 0A, 0B, 0C, 0D, 0E, 0F, 10 ...

Each hexadecimal digit represents four binary digits (bits)—also called a nibble.

To convert the base-16 hexadecimal value 0xA0FF to its base-10 decimal equivalent, hexadecimal progresses from right to left using the following places that represent a power of 16, starting with 16^0:

 4096   256   16   1 A      0    F    F

Given that A=10 and F=15 in hex, the decimal result is calculated as follows:

 (10 x 4096) + (0 x 256) + (15 x 16) + (15 x 1) = 41215 

Source: Wikipedia