Half adder... sum and carry

Thread Starter

fadax

Joined Apr 19, 2010
4
Hi
I am revising for an exam next week and I came across this question when answering questions about computer arithmetic:

http://i40.tinypic.com/15dmkvt.png

I am confused because the truth table shows S=1, C=1 for a half adder with inputs A=1, B=1. But I learnt that with these inputs, a half adder would always output S=0, C=1. (making the sum function XOR, not OR)

So why is it different here? I thought it might be a mistake in the question.. or am I missing something??

thanks
 
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