BCD
Binary-Coded Decimal
                                                     
BCD is a way to represent decimal numbers in a more
compact way than ASCII text. One byte represents two
digits:

01H = 1 decimal
20H = 20 decimal (not 32)
99H = 99 decimal (not 153)
                                                     
  BCD is used rarely on PCs and in PC programming.
  Note that hex digits A-F are never used, so numbers
such as 0aH or b1H are invalid as BCD values.

qBCD