# Circuit that multiples two numbers together?

Design a combinational circuit that multiplies two numbers together, and outputs the result.

The biggest product will be 3 * 3 = 9. Four bits to represent the product.

0: 00
1: 01
2: 10
3: 11


I need a 4 bit register for the outputs, right?

How do I start my truth table? like this?

A B C D | Output | AB | CD
0 0 0 0   0         0    0


and so onto minterm 15?

How will I form the expressions from the truth table? I know how to solve with a K-map, but I'm having a hard time visualizing and building it.