Arduino code: setup, loop and the Serial Monitor

A sketch is simplified C++. setup() — preparation: pinMode, Serial.begin(9600). loop() — the main loop. Serial.println("text") sends text to the computer — open the Serial Monitor and see what the board is "thinking": your main debugging tool. Variables: int sensor = analogRead(A0); if (sensor > 500) { ... }. A code error → it won’t compile, the IDE underlines the line. Typical traps: a forgotten ; at line end and delay(), which "freezes" the whole board.

• ●digitalWrite(pin, HIGH/LOW) — switch a pin on/off
• ●digitalRead(pin) — read a button
• ●millis() instead of delay() — the board doesn’t "sleep" and handles several things at once