Hex numbers are primarily used as a shorthand for the binary numbers that
  computers work with. Every hex digit represents 4 bits of binary
  information. (See Figure B-2.) In the binary (base 2) numbering system, a
  4-bit number can have 16 different combinations, so the only way to
  represent each of the 4-bit binary numbers with a single digit is to use a
  base-16 numbering system. (See Figure B-3.)

  When you're using 2-byte words, remember the reverse, or "back-words,"
  order in which they are stored in memory. See Chapter 2, page 24.

  Hex                      Bits
  --------------------------------------------------------------------------
  0                        0000
  1                        0001
  2                        0010
  3                        0011
  4                        0100
  5                        0101
  6                        0110
  7                        0111
  8                        1000
  9                        1001
  A                        1010
  B                        1011
  C                        1100
  D                        1101
  E                        1110
  F                        1111
  --------------------------------------------------------------------------

  Figure B-2.  The bit patterns for each of the 16 hex digits.

                                                              Value
  Bit   Word                              Byte             Dec      Hex
  --------------------------------------------------------------------------
  0     . . . . . . . . . . . . . . . 1   . . . . . . . 1       1     01H
  1     . . . . . . . . . . . . . . 1 .   . . . . . . 1 .       2     02H
  2     . . . . . . . . . . . . . 1 . .   . . . . . 1 . .       4     04H
  3     . . . . . . . . . . . . 1 . . .   . . . . 1 . . .       8     08H
  4     . . . . . . . . . . . 1 . . . .   . . . 1 . . . .      16     10H
  5     . . . . . . . . . . 1 . . . . .   . . 1 . . . . .      32     20H
  6     . . . . . . . . . 1 . . . . . .   . 1 . . . . . .      64     40H
  7     . . . . . . . . 1 . . . . . . .   1 . . . . . . .     128     80H
  8     . . . . . . . 1 . . . . . . . .                       256    100H
  9     . . . . . . 1 . . . . . . . . .                       512    200H
  10    . . . . . 1 . . . . . . . . . .                      1024    400H
  11    . . . . 1 . . . . . . . . . . .                      2048    800H
  12    . . . 1 . . . . . . . . . . . .                      4096   1000H
  13    . . 1 . . . . . . . . . . . . .                      8192   2000H
  14    . 1 . . . . . . . . . . . . . .                    16,384   4000H
  15    1 . . . . . . . . . . . . . . .                    32,768   8000H
  --------------------------------------------------------------------------

  Figure B-3.  The hexadecimal and decimal equivalents of each bit in a byte
  and each bit in a 2-byte word.