| 摘要 |
A calculator comprises an input having an UNDO key for recovering cleared values. When displayed data or recorded data of memory is cleared by pressing one of deletion keys, the cleared data is pushed into a stack register. A flag register is set when the displayed data or recorded data is cleared by a deletion key. When the UNDO key is pressed and the flag register indicates that the displayed data or recorded data was cleared by the deletion key, a data entry is popped from the stack register, so as to recover the cleared value.
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