Q.Draw the circuit diagram, how you can form an AND and an OR gate using two or more NAND gates.

Using NAND as a universal gate: an AND gate needs two NANDs (a NAND followed by a NAND-inverter), and an OR gate needs three NANDs (invert each input, then NAND the two inverted inputs), which by De Morgan's theorem gives A + B.

Key fact: a NAND gate with its two inputs joined together acts as a NOT gate, because (A.A)' = A'.

AND gate from NAND gates (2 NANDs):

• Circuit: inputs A and B go to the first NAND, whose output is (A.B)'. This output is then fed to BOTH inputs of a second NAND (which acts as an inverter).
• Result: output = ((A.B)')' = A.B. This is the AND function.
• Diagram in words: [A, B] -> NAND1 -> node X = (AB)'; X -> (both inputs of) NAND2 -> output = AB.

OR gate from NAND gates (3 NANDs):

• By De Morgan's theorem, A + B = (A'.B')'. …