BASE 16 or THE HEXADECIMAL CODE

First, let's look at the number system we are most familiar with. Maybe you didn’t know it, but our number system is a "base 10" system. That just means that we group things together in tens. Take the number 10 for example:
10 stands for 1 group of ten and nothing left over; we say "one ten and no ones".
23 stands for 2 groups of ten and three left over; we say "two tens and three ones".

Our numbers look like this:
0,1,2,3,4,5,6,7,8,9 and then, since we have one whole group of “ten”: we write:10—one group of tens and no ones.