Arduino - 74HC595 2

/*
Using 2 7-segment displays with the 74HC595 shift registers
CC by-sa-nc 3.0
http://tronixstuff.wordpress.com
 */
int latchpin = 8; // connect to pin 12 on the '595
int clockpin = 12; // connect to pin 11 on the '595
int datapin = 11; // connect to pin 14 on the '595
float b = 0;
int c = 0;
float d = 0;
int e = 0;
int speed = 300; // used to control speed of counting
int segdisp[10] = {
 3,159,37,13,153,73,65,27,1,9 };
void setup()
{
 pinMode(latchpin, OUTPUT);
 pinMode(clockpin, OUTPUT);
 pinMode(datapin, OUTPUT);
}
void loop()
{
 //  Count up
 for (int z=0; z<100; z++)
 {
   digitalWrite(latchpin, LOW);
   shiftOut(datapin, clockpin, LSBFIRST, 0); // clears the right display
   shiftOut(datapin, clockpin, LSBFIRST, 0); // clears the left display
   digitalWrite(latchpin, HIGH);
   if (z<10)
   {
     digitalWrite(latchpin, LOW);
     shiftOut(datapin, clockpin, LSBFIRST, segdisp[z]); // sends the digit down the serial path
     shiftOut(datapin, clockpin, LSBFIRST, 255); // sends a blank down the serial path to push the digit to the right
     digitalWrite(latchpin, HIGH);
   }
   else if (z>=10)
   {
     d=z%10; // find the remainder of dividing z by 10, this will be the right-hand digit
     c=int(d); // make it an integer, c is the right hand digit
     b=z/10; // divide z by 10 - the whole number value will be the left-hand digit
     e = int(b); // e is the left hand digit
     digitalWrite(latchpin, LOW); // send the digits down to the shift registers!
     shiftOut(datapin, clockpin, LSBFIRST, segdisp[c]); 
     shiftOut(datapin, clockpin, LSBFIRST, segdisp[e]); 
     digitalWrite(latchpin, HIGH);
   }
   delay(speed);
 }
 delay(2000);
 //  Count down
 for (int z=99; z>=0; z--)
 {
   digitalWrite(latchpin, LOW);
   shiftOut(datapin, clockpin, LSBFIRST, 0); // clears the right display
   shiftOut(datapin, clockpin, LSBFIRST, 0); // clears the left display
   digitalWrite(latchpin, HIGH);
   if (z<10)
   {
     digitalWrite(latchpin, LOW);
     shiftOut(datapin, clockpin, LSBFIRST, segdisp[z]); // sends the digit down the serial path
     shiftOut(datapin, clockpin, LSBFIRST, 255); // sends a blank down the serial path to push the digit to the right
     digitalWrite(latchpin, HIGH);
   }
   else if (z>=10)
   {
     d=z%10; // find the remainder of dividing z by 10, this will be the right-hand digit
     c=int(d); // make it an integer, c is the right hand digit
     b=z/10; // divide z by 10 - the whole number value will be the left-hand digit
     e = int(b); // e is the left hand digit
     digitalWrite(latchpin, LOW); // send the digits down to the shift registers!
     shiftOut(datapin, clockpin, LSBFIRST, segdisp[c]); 
     shiftOut(datapin, clockpin, LSBFIRST, segdisp[e]); 
     digitalWrite(latchpin, HIGH);
   }
   delay(speed);
 }
 
   delay(2000);
}