The number of all possible matrices of order 2 × 2 with each entry 0 or 1 is :

27 18 16 81

16

Order = 2 × 2 ⇒  No. of cells = 4 each cell has two possibilities ("0" or "1") So no. of possible matrices = $\underbrace{2 \times 2 \times 2 \times 2}_{4 \text { times }}=24=16$