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Definition: half-adder


An elementary electronic circuit in the arithmetic logic unit (ALU) that adds one bit to another. The output is the result bit and the carry bit. Just like 9 + 1 derives 0 with a carry of 1, in binary, 1 + 1 yields the same results. See binary and ALU.

   INPUTS     OUTPUTS
  Bit Bit  Result  Carry
   1   2    Bit     Bit

   0 + 0  =  0     0

   0 + 1  =  1     0

   1 + 0  =  1     0

   1 + 1  =  0     1