1. An electronic data processing apparatus comprising: an input means for entering data processing functions including numeric data and a plurality of operational commands, said operational commands including at least one unary operational command corresponding to a data processing operation having a single operand, and including at least one unary operation completing command; and arithmetic means for performing entered data processing functions and generating a numeric result, said arithemtic means including a unary operation means for performing unary operational commands upon entry of a unary operation completing command employing the numeric data entered after entry of said unary operational command as the operand if numeric data is entered after entry of said unary operational command prior to entry of said unary operation completing command, and for performing entered unary operational commands on the numeric data entered prior to entry of said unary operational command if no numeric data is entered following entry of said unary operational command prior to entry of said unary operation completing command; and an output means for generating an operator perceivable indication of said numeric result generated by said arithmetic means.