A functional introduction of Arduino hardware

1.Digital I/O(in and out) pins:

In the 14 digital pins, they can both be input and output. You can change the function by using the following functions: pinMode(), digitalWrite(), and digitalRead() {output }.

2. Special features:

Some of the pins even have special features.

The first two, are 0(RX) and 1 (TX). The feature they get is Softwareserial.These two pins can receive and send the data through a Bluetooth module. The reason why they can do that, is because of the settings of Arduino itself. You can even shift this feature by coding.  

PWM pins are the pins marked with ‘‘~’’. They can provide 8-bits PWM output by using the analogWrite() function.

External interruption. Pin two and three can be interrupted by external control.

For the final one 10 (SS), 11 (MOSI), 12 (MISO) and 13 (SCK), these four pins can communicate with external devices.