## 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.