Question

How to convert decimal to binary by hand?

Answer 1

You have to divide decimal number by 2 and then to write the reminder. Then you have to continue to divide the result by 2 and so on. At the end you have to read all those reminders ( numbers 0 and 1 ) backwards and you will get the binary number. Example: Convert 10 ( decimal ) to binary.
10 : 2 = 5  |   0
  5 : 2 = 2  |   1
  2 : 2 = 1  |   0
  1 : 2 = 0  |   1
                        ↑
Finally:  10 ( decimal ) = 1010 ( binary )