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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 inputs.
Iteration with a "for" structure over input pins. button switches are wired from pins 0 to 3 depending the number of pressed buttons a variable named "force" will hold different values from 0 to 4

    int force;

    void setup() {
      Serial.begin(9600);
      for(int i = 0; i<4; i++) {  // sets pins 0-3 as inputs
        pinMode(i, INPUT);
      }
    }

    void loop() {
      force = 0;
      for(int i = 0; i<4; i++) {  // calculates how many buttons are pressed
        if(digitalRead(i) == HIGH) {
          force = force + 1;  // add 1 to force if the button is pressed
        }
      }
      Serial.print("force is: ");  // print the force value
      Serial.println(force);
      delay(200);  // wait 200ms for next reading
    }