说明：   As in hand multiplication (see Figure 2), we multiply the bits of the multiplier A (a3a2a1a0) by the multiplicand (B) starting from the LSB (a0) to the MSB (a3). This forms 4 partial products a0B, a1B, a2B, and a3B. The resulting partial products are added with each product shifted lefts by one bit position from its predecessor as shown in