This ALU as shown above contains three input control signals:

The Logic$\_$Arith$\_$l signal operates so that when Logic$\_$Arith$\_$l $=0,$ an arithmetic operation is performed.

When Logic$\_$Arith$\_$l $=1,$ a logic operation is performed by the ALU.

The Invert$\_$l signal, when active, indicates that some type of inversion, either a one's or two's

complement is taking place.

The A$\_$Only$\_$l signal, when active, indicates that only the A operand is being acted upon by the ALU.

Once this notation is understood, you may be able to fill out the function definition table below for this circuit. Consider the example line in Table $4$:

Logic$\_$Arith$\_$l $=0$ implies the operation is arithmetic.

Invert$\_$l $=1$ implies that A is not inverted $($neither a one's nor a two's complement is performed.$)$

A$\_$Only$\_$l $=1$ implies that the A and B operands are combined in some fashion.

The only two$-$operand, noninverting arithmetic operation of which our ALU is capable is the sum, A $+$ B