POP 同 POS??

Point of sale or point of service (POS or PoS) can mean a retail shop, a checkout counter in a shop, or the location where a transaction occurs. More specifically, the point of sale often refers to the hardware and software used for checkouts -- the equivalent of an electronic cash register. Point of sale systems are used in supermarkets, restaurants, hotels, stadiums, and casinos, as well as almost any type of retail establishment.
Point of sale is from the seller's view while the Point of purchase is from the purchser's view. Point of sale or Point of purchase is the place where sales/purchases are transacted and can therefore maybe the same and hence can mean the same thing (i.e. POP = POS). It depends the angle you look at, from the position of yourself as a seller or as a customer. This is quite crucial when you are looking from these angles. Customer is the King? you, as a seller then put more effort in advertsiing, promotion in POP...