To add hex numbers, you work digit by digit, exactly as you do with
  decimal numbers. To make addition easier, use Figure B-6, which shows the
  sum of any two hex digits. To use this table, find the row for one hex
  digit and the column for the other. The hex number located at the
  intersection of the row and column is the sum of the two digits.

  +--------------------------------------------------+
  |  | 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| A| B| C| D| E| F|
  ---+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
  | 0| 0| 1| 2| 3| 4| 5| 6| 7| 8| 9| A| B| C| D| E| F|
  |--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
  | 1|  | 2| 3| 4| 5| 6| 7| 8| 9| A| B| C| D| E| F|10|
  |--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
  | 2|  |  | 4| 5| 6| 7| 8| 9| A| B| C| D| E| F|10|11|
  |--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
  | 3|  |  |  | 6| 7| 8| 9| A| B| C| D| E| F|10|11|12|
  |--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
  | 4|  |  |  |  | 8| 9| A| B| C| D| E| F|10|11|12|13|
  |--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
  | 5|  |  |  |  |  | A| B| C| D| E| F|10|11|12|13|14|
  |--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
  | 6|  |  |  |  |  |  | C| D| E| F|10|11|12|13|14|15|
  |--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
  | 7|  |  |  |  |  |  |  | E| F|10|11|12|13|14|15|16|
  |--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
  | 8|  |  |  |  |  |  |  |  |10|11|12|13|14|15|16|17|
  |--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
  | 9|  |  |  |  |  |  |  |  |  |12|13|14|15|16|17|18|
  |--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
  | A|  |  |  |  |  |  |  |  |  |  |14|15|16|17|18|19|
  |--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
  | B|  |  |  |  |  |  |  |  |  |  |  |16|17|18|19|1A|
  |--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
  | C|  |  |  |  |  |  |  |  |  |  |  |  |18|19|1A|1B|
  |--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
  | D|  |  |  |  |  |  |  |  |  |  |  |  |  |1A|1B|1C|
  |--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
  | E|  |  |  |  |  |  |  |  |  |  |  |  |  |  |1C|1D|
  |--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
  | F|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |1E|
  +--------------------------------------------------+

  Figure B-6.  Addition of two hex numbers.