#72 – Hexadecimal Numbers

In C#, integer literals are normally specified using base-10 notation (e.g. 123), but can also be specified as a base-16 (hexadecimal or hex) number.

Each hex digit represents a 4-bit value and can therefore represent a value in the range [0,15].  Values from 0-9 are represented by their decimal digits.  Values from 10-15 are represented by the hex digits A-F.

In C#, hex literals begin with the characters “0x”.

Each hex digit represents a value to be multiplied by a power of 16.

Example: 0x1A2F = (1 x 16³) + (10 x 16²) + (2 x 16¹) + (15 x 16⁰) = 4096 + 2560 + 32 + 15 = 6703

You can also think of each hex digit as representing four bits:

0 = 0000
1 = 0001
2 = 0010
…
E = 1110
F = 1111

So 0x1A2F would be:  0001 1010 0010 1111

In C#, you can use hex numbers for integer literals.

 int n = 0x1A2F;
 ushort u1 = 0xFFFF;         // 16 bits
 uint u2 = 0x12341234;       // 32 bits

Hex numbers are a convenient way of expressing integral values, denoting exactly the bits stored in memory for that integer.