Please have a look on the attachment. I have implemented F using NAND gates; not sure if the implementation is correct, please check it. F is a POS term. Someone was saying that he has read somewhere that POS or SOP (not really sure and I didn't ask him) cannot be implemented using NAND gate logic. If he was referring to the POS, then that would mean my implementation is incorrect. Please help me with it. Thanks a lot.
I will say without qualification that any digital system can be implemented with only NAND gates, or its complement, only NOR gates. Those two are known as universal gates. The same is not true for AND or OR gates. No matter how much of a whiz you are at implementing logic gates, you cannot make a inverter with only AND or OR gates.