How this calculator works?

A basic explanation as to how calculations are performed in a simple four-function calculator: To perform the calculation 30 + 4, one presses keys in the following sequence on most calculators: 3 0 + 4 =.

  • When 3 0 is entered, it is picked up by the scanning unit; the number 30 is encoded and sent to the X register;
  • Next, when the + key is pressed, the "addition" instruction is also encoded and sent to the flag or the status register;
  • The second number 4 is encoded and sent to the X register. This "pushes" (shifts) the first number out into the Y register;
  • When the = key is pressed, a "message" (signal) from the flag or status register tells the permanent or non-volatile memory that the operation to be done is "addition";
  • The numbers in the X and Y registers are then loaded into the ALU and the calculation is carried out following instructions from the permanent or non-volatile memory;
  • The answer, 34 is sent (shifted) back to the X register. From there, it is converted by the binary decoder unit into a decimal number (usually binary-coded decimal), and then shown on the display panel.