unsigned long startMillis=0;  //some global variables available anywhere in the program
unsigned long currentMillis;
unsigned long period;
byte numbers[11][7] = {
  { 1, 0, 0, 1, 1, 1, 1 },  //E
  { 0, 1, 1, 0, 0, 0, 0 },  //1
  { 1, 1, 0, 1, 1, 0, 1 },  //2
  { 1, 1, 1, 1, 0, 0, 1 },  //3
  { 0, 1, 1, 0, 0, 1, 1 },  //4
  { 1, 0, 1, 1, 0, 1, 1 },  //5
  { 1, 0, 1, 1, 1, 1, 1 },  //6
  { 1, 1, 1, 0, 0, 0, 0 },  //7
  { 1, 1, 1, 1, 1, 1, 1 },  //8
  { 1, 1, 1, 1, 0, 1, 1 },  //9
  { 1, 0, 0, 0, 1, 1, 1 }   //F
};
byte segmentPin[7] = { 0, 1, 2, 3, 4, 5, 6 };
void display_number(int num) {
  for (int i = 0; i < 7; i++) digitalWrite(segmentPin[i], numbers[num][i]);
}

void startup() {
  for (int i = 0; i < 6; i++) {
    digitalWrite(i, HIGH);
     currentMillis = millis();                 //get the current "time" (actually the number of milliseconds since the program started)
    if (currentMillis - startMillis >= 500)  //test whether the period has elapsed
    {
      digitalWrite(i, LOW);//if so, change the state of the LED.  Uses a neat trick to change the state
      startMillis = currentMillis;  //IMPORTANT to save the start time of the current LED state.
    }
   
  }
}

void setup() {
for (int i = 0; i < 7; i++) {
    pinMode(i, OUTPUT);
  }// put your setup code here, to run once:
 
}

void loop() {
  period=6000;
    
   for (int i = 0; i < 2; i++) {
    currentMillis = millis();   
    if (currentMillis - startMillis >= period)  //test whether the period has elapsed
    {
      digitalWrite(i, !digitalRead(i));//if so, change the state of the LED.  Uses a neat trick to change the state
      startMillis = currentMillis;  //IMPORTANT to save the start time of the current LED state.
    }
  }

}