■ Initialize the calculator
When you are not sure of the current calculator setting, you are recommended to initialize the calculator (resets calculation mode to "COMP", angle unit to "Degree", clears replay and variable memories, and resets LCD contrast) by performing the following key operations:
【SHIFT】 【DEL】 【3】 【=】 【ON/CA】
ㄴ CANON F 789 SGA 매뉴얼 발췌
CANON 계산기 초기화 방법과 유사하네요.