Added comments to Basics examples

build/shared/examples/1.Basics/DigitalReadSerial/DigitalReadSerial.ino

@@ -5,14 +5,23 @@
  This example code is in the public domain.
  */
 
+// digital pin 2 has a pushbutton attached to it. Give it a name:
+int pushButton = 2;
+
+// the setup routine runs once when you press reset:
 void setup() {
+  // initialize serial communication at 9600 bits per second:
   Serial.begin(9600);
-  pinMode(2, INPUT);
+  // make the pushbutton's pin an input:
+  pinMode(pushButton, INPUT);
 }
 
+// the loop routine runs over and over again forever:
 void loop() {
-  int sensorValue = digitalRead(2);
-  Serial.println(sensorValue);
+  // read the input pin:
+  int buttonState = digitalRead(pushButton);
+  // print out the state of the button:
+  Serial.println(buttonState);
 }