Absolute value of the difference. The operands $($ and $)$ are $4-$bit

unsigned numbers. The operation is $=||.$

$$ This circuit can be built out of two $5-$bit adders, $5$ NOT gates, and $5$ XOR

gates as depicted in the figure.

$$ The output of the top $5-$bit adder is $=,$ where $=43210.$

$$ For this adder: cin$=1,$ cout is unused.

$$ The output of the bottom $5-$bit adder is $=||=||.$

$$ For this adder: cin$=$r$4,$ cout is unused.

$$ Given the result $=43210,$ it can be demonstrated that $4=0.$

Thus, it is very common to only use $3210$ as the $4-$bit unsigned result

of $=||.$