What is a "BCD adder," and why can't a standard binary adder be used directly to add two BCD digits?
Correct! Well done.
Incorrect.
The correct answer is A) A BCD adder adds two 4-bit BCD digits plus carry and adds 6 (0110) whenever the binary sum exceeds 9, keeping the result a valid BCD digit; a plain binary adder alone would produce invalid codes for sums between 10 and 19
Correct Answer
A BCD adder adds two 4-bit BCD digits plus carry and adds 6 (0110) whenever the binary sum exceeds 9, keeping the result a valid BCD digit; a plain binary adder alone would produce invalid codes for sums between 10 and 19
Because BCD only uses codes 0000-1001 (0-9) for each digit, a binary sum of two digits that falls between 1010 (10) and 10011 (19) is not a valid BCD representation; adding 6 corrects the result back into valid BCD range with the proper carry into the next digit position.