Parts of a Calculator
There are the obvious parts to a calculator that everyone can see. The buttons (or keys), the plastic front and back pieces and the screws that hold the whole calculator together. Then there are a few parts that you can't see unless you take the calculator apart. If you have an old calculator you may want to do that so you can see what the parts actually look like. The keyboard membrane and keyboard sensors are programmed to know which key you are pressing and in what order. They are also programmed to know what to do when you give it a command such as add or subtract. You can see the front of the display case. The lithium battery gives the calculator the power it needs to function. Some calculators are solar powered and you need to make sure you are in a brightly lit room for them to work. They get their power from the sun or artificial lights.
Press The Keys
When you press the numbers on the keypad, you press rubber buttons that are underneath each key. These rubber buttons stick up, but are hollow (have a pocket of air) underneath. The rubber button makes electrical contact with the keyboard sensor placed below it.
The information is then sent to the processor chip in the calculator. The processor chip determines which keys you have pressed. Then the processor chip sends the information to a screen that you can read (the display box).
After the first set of numbers displayed and you make a call for action (add, minus, multiply, etc.), the calculator stores the first set of numbers in it's register. This is it's memory area. After you tell the calculator the second number and press the equal button, the calculator will fetch the stored information and complete the problem displaying the answer in your display box.
Each number uses a combination of seven lines. All the lines are used to display the number 8. The calculator knows which combination of lines to use for all the numbers it needs from 0-9. So when you press on the number you want it can go in to it's memory and pull out the correct display of lines which forms the number you pushed.