# hexadecimal

numeral system in base 16: it uses 16 digits, from 0 to 9 and from 'a' to 'f'.

there's a direct mapping between each possible combination of 4 bits (nibble), and an hexadecimal (hex) digit:

+ <table>
+ <tr><th>binary</th><th>hex</th><th>dec</th></tr>
+ <tr><td>0000</td><td>0</td><td>0</td></tr>
+ <tr><td>0001</td><td>1</td><td>1</td></tr>
+ <tr><td>0010</td><td>2</td><td>2</td></tr>
+ <tr><td>0011</td><td>3</td><td>3</td></tr>
+ <tr><td>0100</td><td>4</td><td>4</td></tr>
+ <tr><td>0101</td><td>5</td><td>5</td></tr>
+ <tr><td>0110</td><td>6</td><td>6</td></tr>
+ <tr><td>0111</td><td>7</td><td>7</td></tr>
+ <tr><td>1000</td><td>8</td><td>8</td></tr>
+ <tr><td>1001</td><td>9</td><td>9</td></tr>
+ <tr><td>1010</td><td>a</td><td>10</td></tr>
+ <tr><td>1011</td><td>b</td><td>11</td></tr>
+ <tr><td>1100</td><td>c</td><td>12</td></tr>
+ <tr><td>1101</td><td>d</td><td>13</td></tr>
+ <tr><td>1110</td><td>e</td><td>14</td></tr>
+ <tr><td>1111</td><td>f</td><td>15</td></tr>
+ </table>

& * 0000 is 0
& * 0001 is 1
& * 0010 is 2
& * 0011 is 3
& * 0100 is 4
& * 0101 is 5
& * 0110 is 6
& * 0111 is 7
& * 1000 is 8
& * 1001 is 9
& * 1010 is a
& * 1011 is b
& * 1100 is c
& * 1101 is d
& * 1110 is e
& * 1111 is f

# 24 bits

24 bits correspond to:

* 3 bytes
* 4 {base64} digits
* 6 hexadecimal digits
* 8 {octal} digits