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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.

Iteration over digital outputs.
Iteration with a "for" structure over output pins. LEDs are wired from pins 0 to 7

    void setup() {
      Serial.begin(9600);
      for(int i = 0; i<8; i++) {  // sets pins 0-7 as outputs
        pinMode(i, OUTPUT);
      }
    }

    void loop() {
      for(int i = 0; i<8; i++) {  // sets pins 0-7 to HIGH
        digitalWrite(i, HIGH);
        delay(100);  // delay to see the sequence
      }
      for(int i = 0; i<8; i++) {  // sets pins 0-7 to LOW
        digitalWrite(i, LOW);
        delay(100);  // delay to see the sequence
      }
    }