What's on the Board + Setup (first Blink)

What you'll learn

• The big black chip is the brain: a microcontroller (ATmega328P), a tiny computer on one chip, 16 MHz — up to 16 million steps a second.
• USB port: power (5 V) + your program from the computer (Uno R3: USB-B, Uno R4: USB-C).
• Round power jack: a battery or adapter, 7–12 V.
• 14 digital pins (0–13): each is on (HIGH) or off (LOW). 6 analog pins (A0–A5): read in-between values, like a knob (0 … 1023). Power pins: 5V, 3.3V, GND.
• The "L" light is wired to pin 13 (LED_BUILTIN). ON = power. TX / RX flash when the board talks to your computer. Reset = your program starts again from the top.
• Setup: 1) download the free Arduino IDE from arduino.cc (Windows, macOS, Linux) 2) plug in the USB cable — the green ON light comes on 3) Tools → Board → Arduino AVR Boards → Arduino Uno 4) Tools → Port → the one that shows your Uno (Windows COM…, Mac /dev/cu.usbmodem…, Linux /dev/ttyACM0) 5) File → Examples → 01.Basics → Blink, then press Upload (→).
• No port in the list? Try another cable — some USB cables only charge (2 wires) and carry no data (a data cable has 4).
• "Done uploading." → the L light blinks: 1 second on, 1 second off.
• Pins read buttons, knobs and sensors, and switch LEDs, buzzers and motors. A pin + a transistor can drive a big motor (Electronics from Zero, Episode 6).