Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. There are a variety of ways that −1 (and negative numbers in general) can be represented in computer systems, the most common being as two's complement of their positive form. Since this representation could also represent a positive integer in standard binary representation, a programmer must be careful not to confuse the two. Negative one in two's complement could be mistaken for the positive integer 2n − 1, where n is the number of digits in the representation (that is, the number of bits in the data type). For example, 111111112 (binary) and FF16 (hex) each represents −1 in two's complement, but represents 255 in standard numeric representation.