Just as all boolean expressions can be implemented with just the NAND function, the same is true for the NOR function. We simply use various combinations of NOR to obtain other basic boolean functions such as AND, OR, and NOT, from which we can build more complex functions. The following should help illustrate this concept. The NOR function is indicated (here at least) by the ↓ (downward arrow) character.

The NOR truth table
  A   B   A↓B
  T   T    F
  T   F    F
  F   T    F
  F   F    T

Consider A↓A
  A   A↓A
  T    F
  F    T
Thus, A↓A is equivalent to ¬A.

Now to find the ∨ (or) function
  A   B   A↓B   (A↓B)↓(A↓B)
  T   T    F       T
  T   F    F       T
  F   T    F       T
  F   F    T       F
So we have (A↓B)↓(A↓B) equivalent to A ∨ B (A or B)

From this point, we can achieve the conjunction (and) function as A∧B is equivalent to ¬(¬A∨¬B).
Therefore, A∧B (A and B) can be represented in NOR terms as