int summation = 0;

void setup() {
  Serial.begin(9600);
  // put your setup code here, to run once:
}

void loop() {
  summation = localAddition(5, 3);
  Serial.println(summation);
  delay(1000);

  globalAddition(1, 2);
  Serial.println(summation);
  // put your main code here, to run repeatedly:
  delay(10); // this speeds up the simulation
}

int localAddition(int a, int b){
  int sum = a + b;
  return sum;
}

void globalAddition(int a, int b){
  summation = a + b;
}