Hexadecimal

Hexadecimal numbers use a 'base' of 16 instead of 2 (binary) or 10 (denary). 16 symbols are needed - the digits 0 to 9 and the letters A-F. A hexadecimal digit can be written as 4 binary digits. Two hexadecimal digits can represent eight binary digits, or a byte.

Binary	Decimal	Hexadecimal
0	0	0
1	1	1
10	2	2
11	3	3
100	4	4
101	5	5
110	6	6
111	7	7
1000	8	8
1001	9	9
1010	10	A
1011	11	B
1100	12	C
1101	13	D
1110	14	E
1111	15	F
00010000	16	10
00010001	17	11
etc.	etc.	etc.

To convert a value from hexadecimal to binary:
First, write out the hexadecimal number to be converted; then, below each digit write the binary equivalent of that digit:

3	F	7	A
0011	1111	0111	1010

So the binary equivalent of 3F7A is 0011 1111 0111 1010
To convert from binary to hexadecimal, simply reverse the process as shown:

0110	1000	0011	1111
6	8	3	F

So the hexadecimal equivalent of 0110 1000 0011 1111 is 683F