General purpose calculator having selective data storage, data conversion and time-keeping capabilities

An electronic calculator comprising:

• an input unit including a plurality of manually operable keys having key codes assigned thereto for entering information into, and initiating mathematical operations performed by, the calculator, said plurality of keys including a class of numeric and non-numeric keys having unique key codes assigned thereto;
• a first memory unit coupled to the input unit for storing information received therefrom and for storing results of operations performed by the calculator;
• a second memory unit coupled to the first memory unit for storing information received therefrom;
• a processing unit having arithmetic means coupled to the input and first memory units for executing mathematical operations performed by the calculator employing the information or results stored in the first memory unit and storing the results of executed operations in the first memory unit, and having control means coupled to the input, first and second memory units, said control means being automatically responsive to the key code of an actuated key on the input unit for selectively transferring a copy of the information or results previously stored in the first memory unit to the second memory unit prior to storing information entered or results initiated by the actuated key in the first memory unit when the actuated key is one of said class of keys;
• and
• an output display unit coupled to the control means to provide visual display of the information stored in the first memory unit;
• the control means also being responsible to the key code of at least one other of the plurality of keys when actuated for selectively transferring a copy of the information entered or results stored in the second memory unit to the first memory unit.