To convert -10 (decimal) to binary:
Repeat the absolute value (| -10 | = 10) of the number by 2 until you get 0 in quotient:
(10 / 2 = 5 R 0)
(5 / 2 = 2 R 1)
(2 / 2 = 1 R 0)
(1 / 2 = 0 R 1)
Put the leftovers to get the binary equivalent:
1010
For an 8-bit cell, the answer is 0000 1010, a 16-bit cell is 0000 0000 0000 1010, etc.
Take one padding by inverting the bits (we will assume that the 8-bit cell contains the final value):
0000 1010
1111 0101
Now take 2 add-ons, adding 1:
1111 0101
+ 1
1111 0110 // final answer
What happens to a 4-bit cell?
The only addition:
1010
0101
Taking the second supplement causes:
0101
+ 1
----
0110
, , ( 0, 1) .