Because a lot of code is needed to make a computer do anything and the binary sets are so long, a system called hexidecimal numbers has been invented to make the coding a bit easier.
The 8 number binary is broken into 2 halves, each possible 4 number sequence is assigned a letter or number.
E.g. 01001101 is 4D so 0100=4 and 1101=D
A good hexadecimal conversion site http://www.mathsisfun.com/binary-decimal-hexadecimal-converter.html