In general, a basic electronic calculator consists of the following components: Power source (mains electricity, battery and/or solar cell) An office calculating machine with a paper printer. To perform the calculation 25 + 9, one presses keys in the following sequence on most calculators: 2 5 + 9 =. When 2 5 is entered, it is picked up by the scanning unit; the number 25 is encoded and sent to the X register; Keypad (input device) – consists of keys used to input numbers and function commands (addition, multiplication, square-root, etc.) Display panel (output device) – displays input numbers, commands and results. Liquid-crystal displays (LCDs), vacuum fluorescent displays (VFDs), and light-emitting diode (LED) displays use seven segments to represent each digit in a basic calculator. Advanced calculators may use dot matrix displays. A printing calculator, in addition to a display panel, has a printing unit that prints results in ink onto a roll of paper, using a prin...