int pinA = 9;  //defines the pin number
int pinB =13;
int pinC = 4;
int pinD = 6;
int pinE = 7;
int pinF = 10;
int pinG = 3;
int D1 = 8;
int D2 = 11;
int D3 = 12;
int D4 = 2;
unsigned long int sec1;
unsigned long int sec2;
unsigned long int sec3; 
unsigned long int sec4;
unsigned long int counter;
unsigned long int frequency = 1000; // 1HZ

// the setup routine runs once when you press reset:
void setup() {                
  // initialize the digital pins as outputs.
  pinMode(pinA, OUTPUT);     
  pinMode(pinB, OUTPUT);     
  pinMode(pinC, OUTPUT);     
  pinMode(pinD, OUTPUT);     
  pinMode(pinE, OUTPUT);     
  pinMode(pinF, OUTPUT);     
  pinMode(pinG, OUTPUT);   
  pinMode(D1, OUTPUT);  
  pinMode(D2, OUTPUT);  
  pinMode(D3, OUTPUT);  
  pinMode(D4, OUTPUT);  
  /*digitalWrite(D1, LOW);
  digitalWrite(D2, LOW);
  digitalWrite(D3, LOW);
  digitalWrite(D4, LOW);*/
}

void loop() {
  // put your main code here, to run repeatedly:
  //determines the counter 
  

  sec4 = (counter/frequency);
  sec3 = (counter/(frequency * 10));
  sec2 = (counter/(frequency * 100));
  sec1 = (counter/(frequency * 1000));

  led1(sec1%10);  //dispay unit place
  delay(5);
  led2(sec2%10);  // display tenth place
  delay(5); 
  led3(sec3%10);  // display hundereth place
  delay(5);
  led4(sec4%10);  // display thousandth place
  delay(5);
  counter = counter+20;
  // delay(200);
}

//define first LED segment to turn on and diplay specific numbers
// Ones Place
void led4(int a){
  digitalWrite(D4, LOW); 
  digitalWrite(D3,LOW);
  digitalWrite(D2, LOW);
  digitalWrite(D1, LOW);
  //switch to the number to call specific it and display
  switch (a) {
    case 0:
      zero();
      break;
    case 1:
      one();
      break;
    case 2:
      two();
      break;
    case 3:
      three();
      break;
    case 4:
      four();
      break;
    case 5:
      five();
      break;
    case 6:
      six();
      break;
    case 7:
      seven();
      break;
    case 8:
      eight();
      break;
    case 9:
      nine();
      break;
  }
  digitalWrite(D4, HIGH); 
  digitalWrite(D3,LOW);
  digitalWrite(D2, LOW);
  digitalWrite(D1, LOW);
}
//define second LED segment to turn on and diplay specific numbers
// Tens Place
void led3(int b){
  digitalWrite(D4,LOW);
  digitalWrite(D3, LOW);
  digitalWrite(D2, LOW);
  digitalWrite(D1, LOW); 
  //switch to the number to call specific it and display 
  switch (b) {
    case 0:
      zero();
      break;
    case 1:
      one();
      break;
    case 2:
      two();
      break;
    case 3:
      three();
      break;
    case 4:
      four();
      break;
    case 5:
      five();
      break;
    case 6:
      six();
      break;
    case 7:
      seven();
      break;
    case 8:
      eight();
      break;
    case 9:
      nine();
      break;
  }
  digitalWrite(D4,LOW);
  digitalWrite(D3, HIGH);
  digitalWrite(D2, LOW);
  digitalWrite(D1, LOW);
}
// Hundreds Place
void led2(int c){
  digitalWrite(D4, LOW); 
  digitalWrite(D3,LOW);
  digitalWrite(D2, LOW);
  digitalWrite(D1, LOW);
  //switch to the number to call specific it and display
  switch (c) {
    case 0:
      zero();
      break;
    case 1:
      one();
      break;
    case 2:
      two();
      break;
    case 3:
      three();
      break;
    case 4:
      four();
      break;
    case 5:
      five();
      break;
    case 6:
      six();
      break;
    case 7:
      seven();
      break;
    case 8:
      eight();
      break;
    case 9:
      nine();
      break;
  }
  digitalWrite(D4, LOW); 
  digitalWrite(D3,LOW);
  digitalWrite(D2, HIGH);
  digitalWrite(D1, LOW);
}
// Thousands Place
void led1(int d){
  digitalWrite(D4, LOW); 
  digitalWrite(D3,LOW);
  digitalWrite(D2, LOW);
  digitalWrite(D1, LOW);
  //switch to the number to call specific it and display
  switch (d) {
    case 0:
      zero();
      break;
    case 1:
      one();
      break;
    case 2:
      two();
      break;
    case 3:
      three();
      break;
    case 4:
      four();
      break;
    case 5:
      five();
      break;
    case 6:
      six();
      break;
    case 7:
      seven();
      break;
    case 8:
      eight();
      break;
    case 9:
      nine();
      break;
  }
  digitalWrite(D4, LOW); 
  digitalWrite(D3,LOW);
  digitalWrite(D2, LOW);
  digitalWrite(D1, HIGH);
}
// 0 to 9 number outputs to display on the segment
void zero(){
  digitalWrite(pinA, LOW);   
  digitalWrite(pinB, LOW);   
  digitalWrite(pinC, LOW);   
  digitalWrite(pinD, LOW);   
  digitalWrite(pinE, LOW);   
  digitalWrite(pinF, LOW);   
  digitalWrite(pinG, HIGH);   
}
void one(){
  digitalWrite(pinA, HIGH);   
  digitalWrite(pinB, LOW);   
  digitalWrite(pinC, LOW);   
  digitalWrite(pinD, HIGH);   
  digitalWrite(pinE, HIGH);   
  digitalWrite(pinF, HIGH);   
  digitalWrite(pinG, HIGH);   
}
void two(){
  digitalWrite(pinA, LOW);   
  digitalWrite(pinB, LOW);   
  digitalWrite(pinC, HIGH);   
  digitalWrite(pinD, LOW);   
  digitalWrite(pinE, LOW);   
  digitalWrite(pinF, HIGH);   
  digitalWrite(pinG, LOW);     
}
void three(){
  digitalWrite(pinA, LOW);   
  digitalWrite(pinB, LOW);   
  digitalWrite(pinC, LOW);   
  digitalWrite(pinD, LOW);   
  digitalWrite(pinE, HIGH);   
  digitalWrite(pinF, HIGH);   
  digitalWrite(pinG, LOW);     
}
void four(){
  digitalWrite(pinA, HIGH);   
  digitalWrite(pinB, LOW);   
  digitalWrite(pinC, LOW);   
  digitalWrite(pinD, HIGH);   
  digitalWrite(pinE, HIGH);   
  digitalWrite(pinF, LOW);   
  digitalWrite(pinG, LOW);     
}
void five(){
  digitalWrite(pinA, LOW);   
  digitalWrite(pinB, HIGH);   
  digitalWrite(pinC, LOW);   
  digitalWrite(pinD, LOW);   
  digitalWrite(pinE, HIGH);   
  digitalWrite(pinF, LOW);   
  digitalWrite(pinG, LOW);     
}
void six(){
  digitalWrite(pinA, LOW);   
  digitalWrite(pinB, HIGH);   
  digitalWrite(pinC, LOW);   
  digitalWrite(pinD, LOW);   
  digitalWrite(pinE, LOW);   
  digitalWrite(pinF, LOW);   
  digitalWrite(pinG, LOW);     
}
void seven(){
  digitalWrite(pinA, LOW);   
  digitalWrite(pinB, LOW);   
  digitalWrite(pinC, LOW);   
  digitalWrite(pinD, HIGH);   
  digitalWrite(pinE, HIGH);   
  digitalWrite(pinF, HIGH);   
  digitalWrite(pinG, HIGH);     
}
void eight(){
  digitalWrite(pinA, LOW);   
  digitalWrite(pinB, LOW);   
  digitalWrite(pinC, LOW);   
  digitalWrite(pinD, LOW);   
  digitalWrite(pinE, LOW);   
  digitalWrite(pinF, LOW);   
  digitalWrite(pinG, LOW);     
}
void nine(){
  digitalWrite(pinA, LOW);   
  digitalWrite(pinB, LOW);   
  digitalWrite(pinC, LOW);   
  digitalWrite(pinD, HIGH);   
  digitalWrite(pinE, HIGH);   
  digitalWrite(pinF, LOW);   
  digitalWrite(pinG, LOW);     
}