1. A computer program for causing a computer: comprising a display device; and a touch panel input device disposed on said display device; to function as a POS registering system comprising: input screen display-controlling means for causing said display device to display an input screen containing a plurality of menu buttons and at least one selection button, each of said menu buttons representing a sales item name of a unique sales item, the selection button being used to select sales item names represented on the menu buttons, and changing the sales item names represented on the menu buttons to those corresponding to the touched selection button when the touching thereon is detected corresponding to an output from said touch panel input device; and a table correlatively containing sales item codes of sales items represented on the menu buttons and entries of sales item data, said sales item data including a name and price of each sales item; wherein when a touching on a menu button on the input screen is detected corresponding to an output from said touch panel input device, entries of sales item data of all sales item names which are capable of being displayed on the touched menu button are retrieved from said table, an entry corresponding to a sales item whose name is displayed on the touched menu button is defined as an entry of designated sales item data among the retrieved entries, entries corresponding to sales items whose names are not displayed on the touched menu button are defined as entries of correction alternative sales item data among the retrieved entries, the entry of the designated sales item data and the entries of the correction alternative sales item data are displayed on said display device in such a manner that the entry of the designated sales item data is displayed in a different format from the entries of correction alternative sales item data, and when an operator selects an entry of correction alternative sales item data displayed on said display device, the selected entry of correction alternative sales item data is treated as an entry to be processed.