An LED is a semiconductor light source, when forward biased, it emits light. LEDs are used mainly to indicate the status of electronic circuits, for example to indicate that power is on or off but nowadays they are used in many applications including lighting and beam detection. In this article we will learn how to connect and switch on and off various LEDs to a microcontroller using Flowcode Compiler. This is the simplest project a beginner in embedded programming can start with before attempting any complex projects. As with most programming languages, our "Hello world" program here it's just a simple switching ON and OFF an LED connected to PORT B bit 0 of a microcontroller.