Combinational circuits: ALU
	ALU is a combinational circuit
		outputs depend only on inputs
		operations performed
			AND
			OR
			ADD
			SUB
			SLT
			Zero (a == b)
	This is an ARITHMETIC/logic unit								(Fig. 4.21)
		What about multiplication?
			Result depends only on inputs
		1	1	1	0	0			Carry
					1	1	1		Multiplicand
					1	0	1		Multiplier
					1	1	1		Partial products
				0	0	0
			1	1	1
		1	0	0	0	1	1		Product
		Can this be done with a combinational circuit?
		Sure, but
			How big is this truth table?
			What would the circuit have to look like?
		This gets rather large even for 4 bits.						Reference:
		Can we split up the problem in groups of 4?						http://www-inst.eecs.berkeley.edu/~cs152/