An electronic apparatus such as an electronic desk-top calculator, word-processor or electronic typewriter having a display unit and a data input keyboard with plural operating modes in which one of a mode display format and a regular display format is selectively displayed on the single display unit. This arrangement provides a low-cost electronic apparatus using a general-purpose display. The display may return automatically to a regular display after a predetermined period of time has elapsed following a mode display, thereby providing a convenient electronic apparatus without excessive operations.
A user-to-calculating device interface for the solution of mathematical equations. The interface allows for the simple construction of equations which may be utilized or stored. Once an equation has been constructed, it may be solved. The preferred embodiment shows a device wherein equations may be solved utilizing an interface which utilizes a minimum number of key strokes. The user interface includes a top-row-keys interface, in which each menu key within a plurality of menu key are used to both store and to calculate a variable. If two labeled menu keys are pressed in succession, the machine calculates a result for the second. Otherwise, pressing a labeled menu key performs an assignment ("=") operation and then stores a number and displays the number in a display line as a variable represented by the menu key pressed. Pressing an unlabeled menu key does nothing.
