1. BCD = Binary Coded Decimal

2. Representing numbers Integers Real numbers
2’s complement is most popular
BCD
Real numbers
Floating point
IEEE 754 standard format is most popular
Fixed point
2’s complement integers (using standard integer arithmetic)
All of the above are supported by IA32!

3. BCD = binary coded decimal
4 bit encoding of 0..9 (decimal)
base 10 base 2 BCD
same
"
"
"
"
"
"
"
"
"
? ? ?

4. BCD = binary coded decimal
4 bit encoding of 0..9 (decimal)
base 10 base 2 BCD
same
"
"
"
"
"
"
"
"
"
… … …
invalid
… … invalid
invalid

5. Why BCD? What happened when we converted 0.10 (base 10) to base 2?
0.10 x 2 =
0.20 x 2 =
0.40 x 2 =
0.80 x 2 =
0.60 x 2 = .

6. Binary and BCD addition