Arduino Multitasking Tutorial - How to use millis() in Arduino Code

In standard Arduino programming, the delay() function pauses the entire microcontroller, stopping all instruction execution until the time elapses. This project implements true non-blocking multitasking using the millis() function, which returns the number of milliseconds elapsed since the Arduino UNO powered on. By continuously reading millis() and comparing it against previously saved timestamp variables, the microcontroller can track the passage of time independently for multiple processes. The circuit connects three LEDs through 470-ohm current-limiting resistors and a push button pulled with a 10k-ohm resistor via a breadboard and jumpers. Instead of waiting sequentially, the microcontroller's main loop constantly polls the button state while simultaneously evaluating whether enough time has passed to toggle the state of each LED. If a button press is detected via the digital input pin, the system responds instantly because execution is never trapped in a blocking delay routine. Each LED maintains its own distinct timing interval, allowing them to blink or update asynchronously. This architectural approach mirrors real-world embedded system design, where microcontrollers must manage user inputs, sensor readings, and output updates concurrently without missing critical events.