Digital Voltmeter with 7 segment display

Let me try the code tag again:

/*
  Read me

  Use all this information at your own risk, i hold no responsibility for any and all indirect or dicrect damage to your arduino, hardware and software of your pc, any electronic devices if you choose to use this information.

  This meter only can measure up to 5V

  This meter cannot measure negative voltage and make sure you connect the probes to the battery in the correct way (red probe(A0) to the positive side of the battery and black probe(GND) to the negative side of the battery)

*/
int a = 13;
int b = 12;
int c = 11;
int d = 10;
int e = 9;
int f = 8;
int g = 7;
int deci = 3;
int gnd1 = 6;
int gnd2 = 5;
int gnd3 = 4;
int gnd4 = 2;
int inp = A0;

float Reading;
int DeciDigit, OneDigit, TenDigit, HundredDigit;

void mask(int num, int aa, int bb, int cc, int dd, int ee, int ff, int gg)
{
  switch (num)
  {
    case 0 :
      digitalWrite(aa, HIGH);
      digitalWrite(bb, HIGH);
      digitalWrite(cc, HIGH);
      digitalWrite(dd, HIGH);
      digitalWrite(ee, HIGH);
      digitalWrite(ff, HIGH);
      digitalWrite(gg, LOW);
      break;

    case 1 :
      digitalWrite(aa, LOW);
      digitalWrite(bb, HIGH);
      digitalWrite(cc, HIGH);
      digitalWrite(dd, LOW);
      digitalWrite(ee, LOW);
      digitalWrite(ff, LOW);
      digitalWrite(gg, LOW);
      break;

    case 2 :
      digitalWrite(aa, HIGH);
      digitalWrite(bb, HIGH);
      digitalWrite(cc, LOW);
      digitalWrite(dd, HIGH);
      digitalWrite(ee, HIGH);
      digitalWrite(ff, LOW);
      digitalWrite(gg, HIGH);
      break;

    case 3 :
      digitalWrite(aa, HIGH);
      digitalWrite(bb, HIGH);
      digitalWrite(cc, HIGH);
      digitalWrite(dd, HIGH);
      digitalWrite(ee, LOW);
      digitalWrite(ff, LOW);
      digitalWrite(gg, HIGH);
      break;

    case 4 :
      digitalWrite(aa, LOW);
      digitalWrite(bb, HIGH);
      digitalWrite(cc, HIGH);
      digitalWrite(dd, LOW);
      digitalWrite(ee, LOW);
      digitalWrite(ff, HIGH);
      digitalWrite(gg, HIGH);
      break;

    case 5 :
      digitalWrite(aa, HIGH);
      digitalWrite(bb, LOW);
      digitalWrite(cc, HIGH);
      digitalWrite(dd, HIGH);
      digitalWrite(ee, LOW);
      digitalWrite(ff, HIGH);
      digitalWrite(gg, HIGH);
      break;

    case 6 :
      digitalWrite(aa, HIGH);
      digitalWrite(bb, LOW);
      digitalWrite(cc, HIGH);
      digitalWrite(dd, HIGH);
      digitalWrite(ee, HIGH);
      digitalWrite(ff, HIGH);
      digitalWrite(gg, HIGH);
      break;

    case 7 :
      digitalWrite(aa, HIGH);
      digitalWrite(bb, HIGH);
      digitalWrite(cc, HIGH);
      digitalWrite(dd, LOW);
      digitalWrite(ee, LOW);
      digitalWrite(ff, LOW);
      digitalWrite(gg, LOW);
      break;

    case 8 :
      digitalWrite(aa, HIGH);
      digitalWrite(bb, HIGH);
      digitalWrite(cc, HIGH);
      digitalWrite(dd, HIGH);
      digitalWrite(ee, HIGH);
      digitalWrite(ff, HIGH);
      digitalWrite(gg, HIGH);
      break;

    case 9 :
      digitalWrite(aa, HIGH);
      digitalWrite(bb, HIGH);
      digitalWrite(cc, HIGH);
      digitalWrite(dd, HIGH);
      digitalWrite(ee, LOW);
      digitalWrite(ff, HIGH);
      digitalWrite(gg, HIGH);
      break;

  }
}

void setup()
{
  pinMode(a, OUTPUT);
  pinMode(b, OUTPUT);
  pinMode(c, OUTPUT);
  pinMode(d, OUTPUT);
  pinMode(e, OUTPUT);
  pinMode(f, OUTPUT);
  pinMode(g, OUTPUT);
  pinMode(deci, OUTPUT);
  pinMode(gnd1, OUTPUT);
  pinMode(gnd2, OUTPUT);
  pinMode(gnd3, OUTPUT);
  pinMode(gnd4, OUTPUT);
  pinMode(inp, INPUT);
  digitalWrite(deci, HIGH);
}

void loop ()
{
  float TempOneDigit;
  int i;
  Reading = (analogRead(inp) * 5.00 / 1023.00);
  HundredDigit = int(Reading) % 10;
  TenDigit = int ((Reading - HundredDigit ) * 10) % 10;
  TempOneDigit = int(Reading * 10);
  OneDigit = int ((Reading - float(TempOneDigit / 10)) * 100) % 10;
  DeciDigit = 0;

  for (i = 0 ; i < 20 ; i++) {
    mask (DeciDigit, a, b, c, d, e, f, g);
    digitalWrite(gnd4, LOW);
    digitalWrite(gnd3, HIGH);
    digitalWrite(gnd2, HIGH);
    digitalWrite(gnd1, HIGH);
    delay(5);
    mask (OneDigit, a, b, c, d, e, f, g);
    digitalWrite(gnd4, HIGH);
    digitalWrite(gnd3, LOW);
    digitalWrite(gnd2, HIGH);
    digitalWrite(gnd1, HIGH);
    delay(5);
    mask (TenDigit, a, b, c, d, e, f , g);
    digitalWrite(gnd4, HIGH);
    digitalWrite(gnd3, HIGH);
    digitalWrite(gnd2, LOW);
    digitalWrite(gnd1, HIGH);
    delay(5);
    mask (HundredDigit, a, b, c, d, e, f , g);
    digitalWrite(gnd4, HIGH);
    digitalWrite(gnd3, HIGH);
    digitalWrite(gnd2, HIGH);
    digitalWrite(gnd1, LOW);
    delay(5);

  }

}

PS: now I can magically include the code tag