• scan the barcode for each item
• retrieve the price from a database
• calculate deductions for items on sale, tax, differential rates for preferred customers
• time and date stamp the transaction
• record the transaction in detail including each item purchased
• record the method of payment
• keep totals for each product or type of product sold as well as total sales for specified periods

Many cash registers are individual computers. They may be DOS, Windows, or UNIX based. Many of them have touch screens.