Patent US 4,158,233

An adaptable programmable calculator is provided by employing a modular read-write and read-only memory unit capable of being expanded to provide the calculator with additional program and data storage functions oriented towards the environment of the user, a central processing unit, and an input-output control unit capable of bidirectionally transferring information between the memory or central processing units and a number of input and output units. The memory, central processor, and input-output control units are controlled by a microprocessor included in the central processing unit. The input and output units include a keyboard for entering alphameric information, including algebraic statements, into the calculator, a magnetic card reading and recording unit, a solid state output display unit capable of displaying every alphabetic and numeric character and many other symbols individually and in a line of one or more alphameric statements, and a printer unit capable of printing on thermally sensitive paper every alphabetic and numeric character and many other symbols individually and in alphameric statements or messages. The calculator includes an implied multiplication feature whereby algebraic statements entered into the calculator are entered without the multiplication operator but are, nevertheless, processed as if the multiplication operator were present at the appropriate points in those algebraic statements.