Patent US 3,976,975

Disclosed is a self-contained data processing unit, preferably a calculator, which includes an output indicator directing the user which data or function entry the system next expects. After initial data and function entries, a permanent store memory generates successive coded representations of the next entry expected. These representations are visually indicated to the user by an output indicator such as a printer, light emitting diodes, or gas discharge tubes allowing the user to input in proper sequence a long series of inputs without referring to a user's guide.