1. A hand-held navigation and flight performance computer comprising: an alphanumeric display having a menu region for displaying a variety of navigation and flight performance functions, a numeric display for displaying input data and output data, and a data identifying region designating a flight or performance parameter corresponding to said input data and output data; a keyboard for entering said input data, said keyboard including a cursor key for selectively designating a navigation or flight performance function in the menu region of said display; processing means interfacing with said display and said keyboard, said processing means causing said display to sequentially prompt for each item of input data of the designated navigational flight performance function by displaying in the data identifying region of the display a flight or performance parameter designator corresponding to each item of said input data, said processing means displaying in the numeric value region of the display sad input data entered through said keyboard in response to the respective prompt, said processing means further calculating said output data from the displayed input data according to formula corresponding to the navigation or flight performance function designated using said keyboard, said processing means further causing said display to display said output data in the numeric value region of the display, said processing means retaining input data of a selected navigation or flight performance function as default values of input data for subsequent execution of the same navigation or flight performance function.