Hewlett-packard Company

Gabe L Eisenstein

Laurence W Grodd

Charles M Patton

William C Wickes

Robert M Miller

Paul J Mcclellan

A calculator programmed for displaying in textbook format a mathematical expression as it is entered. This format is the way the expression would appear if presented in a textbook or if written with pencil and paper. As a key is pressed, the associated object, such as an alpha character or mathematical symbol, appears on the display screen in textbook format. A cursor is provided which responds to currently entered objects for indicating where the next object to be entered will be displayed. In displaying objects, the calculator is also context sensitive. It responds to currently entered objects by controlling the display of the next object to maintain the textbook format of the expression. Other features include syntax checking of the mathematical expression as its objects are being entered, and implicit entering and displaying of objects in response to entry of a predetermined pattern of objects.

Method and apparatus for displaying and editing mathematical expressions

A calculator is defined by a user-interface centered around a last in first out stack of mathematical or logical objects, that is both visible and accessible to a user. Objects may be any of a number of different types, each type characterized by specific logical or mathematical rules. Calculator operations are provided that may be applied in a uniform manner to the objects, affecting either or both the internal composition of the objects or the external positions and number of the objects on the stack. Objects of different types are distinguished upon entry on the stack and in visible display by characteristic prefix and postfix symbols, and can be entered from a keyboard or created dynamically as the result of calculator operations.

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Corvallis, OR, United States of America

Gabe L Eisenstein