int a = 3;
int b = 4;
int c = 5;
int d = 6;
int e = 7;
int f = 8;
int g = 9;

const int numbers[10][7] = {
  {1, 1, 1, 1, 1, 1, 0}, 
  {0, 1, 1, 0, 0, 0, 0}, 
  {1, 1, 0, 1, 1, 0, 1}, 
  {1, 1, 1, 1, 0, 0, 1}, 
  {0, 1, 1, 0, 0, 1, 1}, 
  {1, 0, 1, 1, 0, 1, 1}, 
  {1, 0, 1, 1, 1, 1, 1}, 
  {1, 1, 1, 0, 0, 0, 0}, 
  {1, 1, 1, 1, 1, 1, 1}, 
  {1, 1, 1, 1, 0, 1, 1} 
};

void setup() {
  for (int i = a; i <= g; i++) {
    pinMode(i, OUTPUT);
  }
}

void loop() {
  for (int num = 9; num >= 0; num--) { 
    displayNumber(num);
    delay(1000);
  }
}

void displayNumber(int num) {
  for (int i = a; i <= g; i++) {
    digitalWrite(i, numbers[num][i - a]);
  }
}