Arduino Calculator using 4x4 Keypad

The Arduino Calculator system operates through a continuous interaction between the 4x4 matrix keypad, the Arduino Uno microcontroller, and the 16x2 LCD display, all powered by a 9V battery. The 4x4 keypad uses a grid of rows and columns to detect button presses. When a user presses a key, the microcontroller scans the rows and columns to identify which specific intersection was closed, mapping it to a corresponding numerical or operational character (such as addition, subtraction, multiplication, or division). The Arduino Uno processes these incoming keystrokes using logic programmed via the Arduino IDE and the specialized Keypad Library, which handles the complex multiplexing logic required to read 16 keys using only 8 pins. As the user enters digits and operators, the Arduino stores them in variables to construct the mathematical expression. Once the equals sign is pressed, the microcontroller executes the calculation and formats the resulting value. Finally, the Arduino sends text data to the 16x2 LCD display via parallel communication, updating the screen in real time so the user can view both their inputted equation and the computed output.