Arduino 4 Digit 7 Segment Display

This instructable is more for its code then any thing else. I remember my beginning days of Arduino, I had a difficulty doing this LED display because I did not have a clear knowledge of Arrays (and i still don't) so I had a hard time finding a examples that did not use Arrays, so after a while I succeeded in making it this way.

So to all the other people who don't understand Arrays here is another way of making a 4 digit 7 segment display work.

int aPin = 2;  //                     A
int bPin = 3;  //             ________
int cPin = 4;  //           |                   |
int dPin = 5;  //       F  |                   |  B
int ePin = 6;  //           |         G       |
int fPin = 7;  //            |________|
int gPin = 8;  //           |                   |
int GND1 = 9;  //        |                   |
int GND2 = 10; //   E |                   |   C
int GND3 = 11; //       |________|
int GND4 = 12; //       
int num;       //         D
int dig1 = 0;
int dig2 = 0;
int dig3 = 0;
int dig4 = 0;
int DTime = 4;


void setup()
{
  pinMode(aPin, OUTPUT);
  pinMode(bPin, OUTPUT);
  pinMode(cPin, OUTPUT);
  pinMode(dPin, OUTPUT);
  pinMode(ePin, OUTPUT); 
  pinMode(fPin, OUTPUT);
  pinMode(gPin, OUTPUT);
  pinMode(GND1, OUTPUT);
  pinMode(GND2, OUTPUT);
  pinMode(GND3, OUTPUT);
  pinMode(GND4, OUTPUT);
  Serial.begin(9600);
}
void loop()
{
  digitalWrite( GND1, HIGH);
  digitalWrite( GND2, HIGH);
  digitalWrite( GND3, HIGH);
  digitalWrite( GND4, HIGH);

if (Serial.available() > 0)
{
  num = Serial.parseInt();
  Serial.println(num);
  dig1 = num / 1000;
  num = num - (dig1 * 1000);
  dig2 = num / 100;
  num = num - (dig2 * 100);
  dig3 = num / 10;
  dig4 = num - (dig3 *10);
}


  digitalWrite( GND4, LOW);    //digit 4
  pickNumber(dig4);
  delay(DTime);
  digitalWrite( GND4, HIGH);

  digitalWrite( GND3, LOW);    //digit 3
  pickNumber(dig3);
  delay(DTime);
  digitalWrite( GND3, HIGH);

  digitalWrite( GND2, LOW);   //digit 2
  pickNumber(dig2);
  delay(DTime);
  digitalWrite( GND2, HIGH);

  digitalWrite( GND1, LOW);   //digit 1
  pickNumber(dig1);
  delay(DTime);
  digitalWrite( GND1, HIGH);

}

void pickNumber(int x){
   switch(x){
     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;
     default: zero(); break;
   }
}

void clearLEDs()
{  
  digitalWrite(  2, LOW); // A
  digitalWrite(  3, LOW); // B
  digitalWrite(  4, LOW); // C
  digitalWrite(  5, LOW); // D
  digitalWrite(  6, LOW); // E
  digitalWrite(  7, LOW); // F
  digitalWrite(  8, LOW); // G
}

void one()
{
  digitalWrite( aPin, LOW);
  digitalWrite( bPin, HIGH);
  digitalWrite( cPin, HIGH);
  digitalWrite( dPin, LOW);
  digitalWrite( ePin, LOW);
  digitalWrite( fPin, LOW);
  digitalWrite( gPin, LOW);
}

void two()
{
  digitalWrite( aPin, HIGH);
  digitalWrite( bPin, HIGH);
  digitalWrite( cPin, LOW);
  digitalWrite( dPin, HIGH);
  digitalWrite( ePin, HIGH);
  digitalWrite( fPin, LOW);
  digitalWrite( gPin, HIGH);
}

void three()
{
  digitalWrite( aPin, HIGH);
  digitalWrite( bPin, HIGH);
  digitalWrite( cPin, HIGH);
  digitalWrite( dPin, HIGH);
  digitalWrite( ePin, LOW);
  digitalWrite( fPin, LOW);
  digitalWrite( gPin, HIGH);
}

void four()
{
  digitalWrite( aPin, LOW);
  digitalWrite( bPin, HIGH);
  digitalWrite( cPin, HIGH);
  digitalWrite( dPin, LOW);
  digitalWrite( ePin, LOW);
  digitalWrite( fPin, HIGH);
  digitalWrite( gPin, HIGH);
}

void five()
{
  digitalWrite( aPin, HIGH);
  digitalWrite( bPin, LOW);
  digitalWrite( cPin, HIGH);
  digitalWrite( dPin, HIGH);
  digitalWrite( ePin, LOW);
  digitalWrite( fPin, HIGH);
  digitalWrite( gPin, HIGH);
}

void six()
{
  digitalWrite( aPin, HIGH);
  digitalWrite( bPin, LOW);
  digitalWrite( cPin, HIGH);
  digitalWrite( dPin, HIGH);
  digitalWrite( ePin, HIGH);
  digitalWrite( fPin, HIGH);
  digitalWrite( gPin, HIGH);
}

void seven()
{
  digitalWrite( aPin, HIGH);
  digitalWrite( bPin, HIGH);
  digitalWrite( cPin, HIGH);
  digitalWrite( dPin, LOW);
  digitalWrite( ePin, LOW);
  digitalWrite( fPin, LOW);
  digitalWrite( gPin, LOW);
}

void eight()
{
  digitalWrite( aPin, HIGH);
  digitalWrite( bPin, HIGH);
  digitalWrite( cPin, HIGH);
  digitalWrite( dPin, HIGH);
  digitalWrite( ePin, HIGH);
  digitalWrite( fPin, HIGH);
  digitalWrite( gPin, HIGH);
}

void nine()
{
  digitalWrite( aPin, HIGH);
  digitalWrite( bPin, HIGH);
  digitalWrite( cPin, HIGH);
  digitalWrite( dPin, HIGH);
  digitalWrite( ePin, LOW);
  digitalWrite( fPin, HIGH);
  digitalWrite( gPin, HIGH);
}

void zero()
{
  digitalWrite( aPin, HIGH);
  digitalWrite( bPin, HIGH);
  digitalWrite( cPin, HIGH);
  digitalWrite( dPin, HIGH);
  digitalWrite( ePin, HIGH);
  digitalWrite( fPin, HIGH);
  digitalWrite( gPin, LOW);
}