Abstract: A compact-size computer such as a functional calculator or a pocket computer selects either the sequential operation mode or formula memory mode according to the purpose of arithmetic operations and promotes faster and easier key operations. Specifically, it is substantially a calculator capable of executing formula calculations with different operational sequences wherein it comprises means for selecting and designating either the sequential operation mode that sequentially executes formula calculations according to individual key operations, or formula memory operation mode that executes operations after entry of the sequential operation mode.

Abstract: A portable electronic computer or calculator is characterized in that it calculates a functional operation on the previously calculated result by simply actuating a function key switch while the result is being displayed. It is unnecessary to actuate any entry key switch. In a specific form of the present invention, the computer may calculate a functional operation on numerical data in response to input of a function command, the numerical data being either newly inputted or previously calculated.