1. A method of displaying in a calculator, comprising: receiving a first mathematical expression in an expression entry area on the calculator; displaying results in a first window on the calculator, wherein the results displayed in the first window comprise a result for the first mathematical expression; displaying, in a second window on the calculator, a usage history comprising the first mathematical expression, a second mathematical expression, and results displayed in the second window, wherein the results displayed in the second window comprise the result for the first mathematical expression and a result for the second mathematical expression, wherein the usage history is displayed in a hierarchical tree such that a result for a given mathematical expression is displayed in the second window on a different hierarchical level than the given mathematical expression; and displaying organizational tabs for the second window, wherein each organizational tab is operable to display a given category of data associated with the usage history, and wherein the results in the first window and the results in the second window are displayed simultaneously.
1. A method of displaying in a calculator, comprising: receiving a first mathematical expression in an expression entry area on the calculator; displaying results in a first window on the calculator, wherein the results displayed in the first window comprise a result for the first mathematical expression; displaying, in a second window on the calculator, a usage history comprising the first mathematical expression, a second mathematical expression, and results displayed in the second window, wherein the results displayed in the second window comprise the result for the first mathematical expression and a result for the second mathematical expression, wherein the usage history is displayed in a hierarchical tree such that a result for a given mathematical expression is displayed in the second window on a different hierarchical level than the given mathematical expression; and displaying organizational tabs for the second window, wherein each organizational tab is operable to display a given category of data associated with the usage history, and wherein the results in the first window and the results in the second window are displayed simultaneously. 4. The method of claim 1 , further including copying the second mathematical expression from the second window to the first window in response to double clicking on the second mathematical expression.