Any Decimal number can be converted into its equivalent binary number. The conversion is obtained by continuous division by 2 and keeping track of the remainders.

Lets see how to convert (13)₁₀ to an equivalent binary number..

               Quotient       Remainder
  13/2            6               1                   
   6/2            3               0
   3/2            1               1
   1/2            0               1

Let me walk through the steps...
13 is divided by 2, the quotient is 6 and remainder 1. Now in step-2, 6 is divided by 2, the quotient is 3 and remainder 0. The process of dividing quotient continues till the quotient becomes zero. The sequence of collected remainders after each step finally gives you binary number.

In the above method we keep dividing quotient till quotient becomes zero. And collected remainder sequence gives binary equivalent i.e 1,0,1,1.

Thus, (13)₁₀ = (1011)₂