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This example is for Wiring version 0024+. If you have a previous version, use the examples included with your software. If you see any errors or have comments, please let us know.

Logical Operators.
The logical operators for AND (&&) and OR (||) are used to combine simple relational statements into more complex expressions. The NOT (!) operator is used to negate a boolean statement.

    int RED = 0;  // red LED on digital pin 0
    int BLUE = 1;  // blue LED on digital pin 0
    boolean op = false;

    void setup() {
      pinMode(RED, OUTPUT);
      pinMode(BLUE, OUTPUT);
    }

    void loop() {
      for(int i=5; i<=195; i+=5) {
        // Logical AND
        if((i > 35) && (i < 100)) {
          op = false;
        }

        // Logical OR
        if((i <= 35) || (i >= 100)) {
          op = true;
        }

        // Testing if a boolean value is "true"
        // The expression "if(op)" is equivalent to "if(op == true)"
        if(op) {
          digitalWrite(RED, LOW);
          digitalWrite(BLUE, HIGH);
          delay(200);  // delay to visualize the LED change
        }

        // Testing if a boolean value is "false"
        // The expression "if(!op)" is equivalent to "if(op == false)"
        if(!op) {
          digitalWrite(RED, HIGH);
          digitalWrite(BLUE, LOW);
          delay(200);  // delay to visualize the LED change
        }
      }
    }