1. An electronic calculator capable of checking data in a memory upon operation of a clear key, comprising: key input means including at least a key for inputting operation data and a clear key for outputting a signal to designate clear processing; memory means connected to said key input means for storing the data input by the operation of said key input means; check data memory means for storing checked data to check a malfunction; reference data generating means for outputting reference data to be compared with the checked data; battery means for supplying power and generating a signal representative of a recovery toward normal battery voltage; discriminating means, connected to both said check data memory means and said reference data generating means, for comparing the checked data with the reference data to see if the checked data has been changed due to a voltage drop in said battery means; clear processing means, connected to said memory means, for clearing part of said memory means; initialization processing means, connected to said memory means, for initializing said memory means; control means coupled to said battery means, said check data memory means, said clear processing means and said initialization processing means for writing the reference data generated from said reference data generating means into said check data memory means when power is supplied from said battery means, for receiving a discrimination result signal from said discriminating means when said clear key is operated, and for generating a control signal in response to the discrimination result signal to cause one of said clear processing means and initialization processing means to perform the associated process.