0000    0   0
0001    1   1
0010    2   2
0011    3   3
0100    4   4
0101    5   5
0110    6   6
0111    7   7
1000    8   -8
1001    9   -7
1010    10  -6
1011    11  -5
1100    12  -4
1101    13  -3
1110    14  -2
1111    15  -1

• Unsigned Integers
  Unsigned integers are unsigned binary numbers contained in a byte, word, doubleword, and quadword.

unsigned byte integer:  range from 0 to 255;
unsigned word integer:  from 0 to 65,535;
unsigned doubleword integer:  from 0 to 2^32– 1  (4,294,967,296-1);
 unsigned quadword integer:  from 0 to 2^64– 1  (約42億*42億);

• Signed Integers
  Signed integers are signed binary numbers held in a byte, word, doubleword, or quadword.

Integer values range 
from –128 to +127 for a byte integer, 
from –32,768 to +32,767 for a word integer,
from –2^31 to +2^31 – 1 for a doubleword integer. 
from –2^63 to +2^63 – 1 for a quadword integer.