How number bases work
Each base uses a set of digits: binary uses 0 and 1, octal uses 0 to 7, decimal uses 0 to 9, and hexadecimal uses 0 to 9 and A to F. Each place is worth the base times the place to its right, so binary 1011 is 8 + 0 + 2 + 1 = 11 in decimal.