keerok
The best example of point of sale is the cash register at the supermarket. Nowadays those are computerized. Not only do they detect the price of the items (with the use of a barcode scanner) and tally the prices for the total payment (like a calculator) but they also update inventory (by connecting to another server in the backroom) so the manager knows exactly when to order more of a particular item (so the shelves won't run out). To run all of that is the program or software that runs in the cashier's computer (which is actually also the cash register).