int a = 2;
int b = 3;
int c = 4;
int d = 5;
int e = 6;
int f = 7;
int g = 8;

void setup() {
  pinMode(a, OUTPUT);
  pinMode(b, OUTPUT);
  pinMode(c, OUTPUT);
  pinMode(d, OUTPUT);
  pinMode(e, OUTPUT);
  pinMode(f, OUTPUT);
  pinMode(g, OUTPUT);
}

void loop() {
  displayNumber(0);
  delay(1000);
  displayNumber(1);
  delay(1000);
}

void displayNumber(int num) {
  switch(num) {
    case 0:
      digitalWrite(a, HIGH); digitalWrite(b, HIGH); digitalWrite(c, HIGH);
      digitalWrite(d, HIGH); digitalWrite(e, HIGH); digitalWrite(f, HIGH); digitalWrite(g, LOW);
      break;
    case 1:
      digitalWrite(a, LOW); digitalWrite(b, HIGH); digitalWrite(c, HIGH);
      digitalWrite(d, LOW); digitalWrite(e, LOW); digitalWrite(f, LOW); digitalWrite(g, LOW);
      break;
  }
}