Temperature on 7 segment common cathode arduino onu

/* Modified by Jeffrey@dutchunderground.nl
 * For common cathode display and LM35 temp sensor. Smooth out display refreshing
 *
 * Original code by Rui Santos, http://randomnerdtutorials.com
 * Temperature Sensor Displayed on 4 Digit 7 segment common anode
 * 2013
 */


const int digitPins[4] = {10,8,9,7};                 //4 common anode pins of the display
const int clockPin = 11;    //74HC595 Pin 11
const int latchPin = 12;    //74HC595 Pin 12
const int dataPin  = 13;     //74HC595 Pin 14
const int tempPin  = A0;     //temperature sensor pin
const byte digit[10] =      //seven segment digits in bits
{
  B11000000, //0
  B11111001, //1
  B10100100, //2
  B10110000, //3
  B10011001, //4
  B10010010, //5
  B10000010, //6
  B11111000, //7
  B10000000, //8
  B10010000  //9
};
const byte digitdec[10] =      //seven segment digits in bits with decimal point
{
  B01000000, //0
  B01111001, //1
  B00100100, //2
  B00110000, //3
  B00011001, //4
  B00010010, //5
  B00000010, //6
  B01111000, //7
  B00000000, //8
  B00010000  //9
};
int digitBuffer[4] = {
  0};
int digitScan = 0, flag=0,  soft_scaler = 0;
;
float tempK, tempC, tempF, temp;

const int numReadings = 10;
 int readings[numReadings];      // the readings from the analog input
int index = 0;                  // the index of the current reading


void setup(){
  for(int i=0;i<4;i++)
  {
    pinMode(digitPins[i],OUTPUT);
  }
  pinMode(tempPin, INPUT);
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
  pinMode(tempPin, INPUT);
  analogReference(INTERNAL); // Set analog input pin to 1.1v for arduino Mega use INTERNAL1V1
}

//writes the temperature on display
void updateDisp(){
  for(byte j=0; j<4; j++)
    digitalWrite(digitPins[j], HIGH);

  digitalWrite(latchPin, LOW);
  shiftOut(dataPin, clockPin, MSBFIRST, B00000000);
  digitalWrite(latchPin, HIGH);

  delayMicroseconds(10);
  digitalWrite(digitPins[digitScan], LOW);

  digitalWrite(latchPin, LOW);
   if(digitScan==0)
    shiftOut(dataPin, clockPin, MSBFIRST, ~B10011110);    // display small c on section 0
   else
   if(digitScan==2)
    shiftOut(dataPin, clockPin, MSBFIRST, ~digitdec[digitBuffer[digitScan]]); // display decimal point at section 2
  else
    shiftOut(dataPin, clockPin, MSBFIRST, ~digit[digitBuffer[digitScan]]);

  digitalWrite(latchPin, HIGH);
  digitScan++;
  if(digitScan>3) digitScan=0;
}

void loop(){

index = index + 1;                     // add to counter
if (index >= 500){                     // read sensor after 500 display updates to smooth out the readings
tempC = analogRead(tempPin);           // read the value from the sensor
index = 0;                             // reset counter
tempC = tempC *10 / 9.31;              // convert sensor readings to celcius degrees
}
  digitBuffer[3] = (int(tempC)%1000)/100;
  digitBuffer[2] = (int(tempC)%100)/10;
  digitBuffer[1] = (int(tempC)%100)%10;
  updateDisp();
  delay(2);

    // ...wrap around to the beginning:

}