Patent ID: 7427013

Claim:
A calculator, comprising: an input pad that includes a sales tax button; and a currency pad, which includes a change due button and a number of currency keys, wherein the currency keys can be depressed in order to enter numeric values associated with currency, and wherein the change due button may be used in order to produce a resultant between data provided in the input pad and the currency pad, wherein the calculator is handheld, and wherein the sales tax button is electronically coupled to a memory within the calculator such that the calculator may be pre-programmed to include two or more numeric values associated with sales tax, wherein when an individual depresses the sales tax button for a prescribed period of time, the pre-programmed numeric values change on a display of the calculator and the displayed numeric value acts as a tax standard for a given calculation, and wherein the calculator includes a solar panel that is operable to power the calculator.