US Patent 7882163 Electronic abacus and operation method of the electronic abacus

An electronic abacus includes a calculating apparatus, an input apparatus and a display apparatus. The input apparatus and the display apparatus are connected to the calculating apparatus respectively. The calculating apparatus receives the input information from the input apparatus, processes the information, and displays the processed information on the display apparatus. The input apparatus includes function keys and number input keys The number input keys include several sets of numeral keys. Each set of the numeral keys is corresponding to one digit of the input information displayed in the display apparatus. Each set of the numeral key includes the keys indicating “5”, “−5”, “4”, “−4”, “3”, “−3”, “2”, “−2”, “1”, “−1” respectively.