Abstract: A programmable calculator is disclosed which includes a display panel for displaying numerical or alphabetical data, and a keyboard for introducing desired numerical or alphabetical data into a space assigned for a variable. The calculator is further adapted to selectively erase the previous contents on the display panel and display only the introduced numerical or alphabetic data upon introduction of the numerical or alphabetic data or to inhibit erasure of the previous contents on the display panel and display the introduced numerical or alphabetic data together with the previous contents upon introduction of the numerical or alphabetic data.

Abstract: In a preferred form of the present invention, upon operation of a particular key a calculator runs a stored program, beginning with a step in the stored program as selected by that particular key. If the program contains a particular instruction at that beginning step, then the calculator serves to insert previous information displayed before the operation of the particular key into a variable column as specified by the instruction.

Abstract: A key-operated digital program calculator is adapted to receive in succession a plurality of different kinds of input data items and perform a specified program calculation thereupon. The calculator is further provided with a display capable of visually displaying which kinds of input data items to be entered thereinto, whereby the operator is visually informed of the kinds of input data items to be next introduced into the calculator.