ELECTRONIC CASH REGISTER WITH MEANS TO STORE AND CORRELATE DATA ON A CUSTOMER BY CUSTOMER BASIS

An electronic cash register of the invention can provide a correlation between sales of items or commodities. The electronic cash register has a PLU code data memory. The PLU code data memory stores PLU code data of items purchased by each customer. In order to calculate the number of customers who buy at least one of two items, a CPU retrieves the contents of the PLU code data memory for each customer. When it is determined upon this retrieval operation that a given customer buys at least one of the two items, the corresponding customer number count is incremented by 1. When the retrieval operation is completely for all the contents stored in the PLU code data memory, the desired information is calculated. Similarly, by counting the number of customers who buy one or both of the two items, and the like, correlations between sales of items can be determined.