On the computer system what is the difference of binary and decimal?

There is no difference. Decimal notation is merely a human convenience. The same rules that apply to decimal also apply to binary, the only difference being that decimal has 10 digits and deals with powers of 10, while binary uses 2 digits and deals with powers of 2. Binary (base-2) is the most primitive form of numeric notation and by far the simplest to implement at the machine level.