LCD Stopwatch, with Split time

#include <LiquidCrystal.h>
//PIN 5 R/W to Ground, for writing
//LCD Mode : 4 data pin
//Functions: Start, stop, saving up to 4 partial time in memory.
//10 millis = 1 hundredth of a second. The chronometer measures hour, minutes, seconds, and hundredths of a second.

//Buttons with internal Pullup, so if they get pressed we get LOW
const int start = 8;  //Start the stopwatch
const int pausa = 9;  //Pausa
const int partial = 10;  //Save a partial
const int scroll_partial = 11;  //If paused, check the 4 last saved partial 
int x = 0; //Variable to manage the loop

//LCD
int lcdclear = 0; //this to variables are needed for managing
int Display = 0; //the display, to clear and print

//chronometer
int cents = 0;
int seconds = 0;  
int minutes = 0;
int hours = 0;
const int interval = 10; //Every 10 milliseconds i increase  1 cent
unsigned long previousMillis = 0;
int c1, c2, s1, s2, m1, m2, h; //Variables used to put in the form 
                              //h:m2m1:s2s1:c2c1

//Partial: I save 4 partial, that can be seen if stopwatch is stopped
int partial2[7]; //penultimate partial (The one that stays in Old). The last partial stays in New:
int partial3[7]; 
int partial4[7]; 
int scrolling = 0; //Used to scroll the saved partial times


LiquidCrystal lcd(2, 3, 4, 5, 6, 7); // RS-Enable-D4-D5-D6-D7 in that digitalPin

void setup() {
  pinMode(start, INPUT_PULLUP); //In the schematic from right to left
  pinMode(pausa, INPUT_PULLUP);//there are start-pausa-partial-scroll_partial
  pinMode(partial, INPUT_PULLUP);
  pinMode(scroll_partial, INPUT_PULLUP);
  lcd.begin(16,2);
  lcd.print("Press start");

}

void loop() {
  if (x == 0) {  //Initially is 0
    while(digitalRead(start) == HIGH) {};  //Until i press the button, the chronometer doesn't start
  x++; //When i press the button, i go out from this cycle, x++ and i cannot return here anymore
  }
  if (lcdclear == 0){   //Condition to clear the display, used in the various functions
    lcd.clear();
    lcdclear++;
  }
  if (Display == 0){ //Also this is used to clear display
  lcd.home();
  lcd.print("Now:  ");  //With this condition, i can print "Now: " one single time, otherwise the chronometer wouldn't be precise
  Display++; 
  scrolling = 0; //When i exit from the partial menu, then if i go in the partial menu again i always get in PAR1 and PAR2
  }              
  chronometer(); //At the end of every increase, i control if stop is pressed. And also if the partial function is pressed
  pause();
  f_partial();
}

void chronometer(void){   //This function print:   "New: Actual time"
  unsigned long currentMillis = millis();  //If for the updating. If it is true, it means 1 cent of a second had passed. Update cents, minutes, seconds, hours and then i write on the lcd
  if (currentMillis - previousMillis >= interval) {  
    previousMillis = currentMillis;
    cents++;
    if (cents == 100){
      cents = 0;
      seconds++;
      if (seconds == 60) {
        seconds = 0;
        minutes++;
        if (minutes == 60){
          minutes = 0; 
          hours++;
          if (hours == 24)
            hours = 0;
          }
      }
   }
    int cent = cents;
    int sec = seconds;
    int minu = minutes; //Taking the digits separeted
    h = hours;  //For the other funcionts, so i can put hours = 0 and h still is the last value
    c1 = cent%10;
    cent /= 10;
    c2 = cent%10;
    s1 = sec%10;
    sec /= 10;
    s2 = sec%10;
    m1 = minu%10;
    minu /= 10;
    m2 = minu%10;
    lcd.setCursor(6, 0);
    lcd.print(h);
    lcd.print(':');
    lcd.print(m2);
    lcd.print(m1);
    lcd.print(':');
    lcd.print(s2);
    lcd.print(s1);
    lcd.print(':');
    lcd.print(c2);
    lcd.print(c1); 
  } 
}

void scrollPartial(void){
    while(digitalRead(scroll_partial) == LOW) {}; //Debounce, as long as i press the button the real function doesn't start
    if (scrolling == 0) { //Visualize the last 2 partials
    lcd.clear(); 
    lcd.home();
    lcd.print("PAR1:");
    lcd.setCursor(6, 0);
    lcd.print(h);
    lcd.print(':');
    lcd.print(m2);
    lcd.print(m1);
    lcd.print(':');
    lcd.print(s2);
    lcd.print(s1);
    lcd.print(':');
    lcd.print(c2);
    lcd.print(c1);
    lcd.setCursor(0, 1);
    lcd.print("PAR2:");
    lcd.setCursor(6, 1);
    lcd.print(partial2[0]);
    lcd.print(':');
    lcd.print(partial2[1]);
    lcd.print(partial2[2]);
    lcd.print(':');
    lcd.print(partial2[3]);
    lcd.print(partial2[4]);
    lcd.print(':');
    lcd.print(partial2[5]);
    lcd.print(partial2[6]); 
    Display = 0; //When i press start the display must be cleared
    lcdclear = 0; //When i press start the display must be cleared
    cents = seconds = minutes = hours  = 0;
    scrolling++;
  }
  else if (scrolling == 1){ //Visualize 3th and 4th partial
    lcd.clear();
    lcd.home();
    lcd.print("PAR3:");
    lcd.setCursor(6, 0);
    lcd.print(partial3[0]);
    lcd.print(':');
    lcd.print(partial3[1]);
    lcd.print(partial3[2]);
    lcd.print(':');
    lcd.print(partial3[3]);
    lcd.print(partial3[4]);
    lcd.print(':');
    lcd.print(partial3[5]);
    lcd.print(partial3[6]);
    lcd.setCursor(0, 1);
    lcd.print("PAR4:");
    lcd.setCursor(6, 1);
    lcd.print(partial4[0]);
    lcd.print(':');
    lcd.print(partial4[1]);
    lcd.print(partial4[2]);
    lcd.print(':');
    lcd.print(partial4[3]);
    lcd.print(partial4[4]);
    lcd.print(':');
    lcd.print(partial4[5]);
    lcd.print(partial4[6]); 
    Display = 0; //When i press start the display must be cleared
    lcdclear = 0; //When i press start the display must be cleared
    cents = seconds = minutes = hours  = 0;
    scrolling = 0;
    
  }
  
} 


void pause(void){  //If pause is pressed, i stop in this function until start doesn't get pressed again
      if (digitalRead(pausa) == HIGH) 
        return;
      else if (digitalRead(pausa) == LOW){ //Stuck in this cycle until i press start
        while(digitalRead(start) == HIGH) {  
          if (digitalRead(scroll_partial) == LOW) //If i press the button for seeing the partial, i enter in that function
            scrollPartial();    //When scrollPartial() ends, i'm still in this function, so if i press start the chronometer starts back normal
          }
    } 
}

void f_partial(void){   //If this button is pressed, i put the current value of New in Old, and a new crhonometer starts
  if (digitalRead(partial) == HIGH)
    return;
  else if (digitalRead(partial) == LOW ){ 
   lcd.clear();
   lcd.setCursor(0, 1); //The values calculated in the function chronometer can be used,  h,m,s,c
   lcd.print("Old: ");
   lcd.setCursor(6, 1);
   lcd.print(h);
   lcd.print(':');
   lcd.print(m2);
   lcd.print(m1);
   lcd.print(':');
   lcd.print(s2);
   lcd.print(s1);
   lcd.print(':');
   lcd.print(c2);
   lcd.print(c1);   //When i come here, i've got the old values for h,m,s,c,                       i save it in the partial array
   Display = 0;   //The new is written again 
   cents = 0;
   seconds = 0;
   minutes = 0;
   hours = 0;

   partial4[0] = partial3[0]; //Partial4[] is updated with the old partial3[]
   partial4[1] = partial3[1];
   partial4[2] = partial3[2];
   partial4[3] = partial3[3];
   partial4[4] = partial3[4];
   partial4[5] = partial3[5];
   partial4[6] = partial3[6];
   
     
   partial3[0] = partial2[0]; //Partial3[] is updated with the old partial2[]
   partial3[1] = partial2[1];
   partial3[2] = partial2[2];
   partial3[3] = partial2[3];
   partial3[4] = partial2[4];
   partial3[5] = partial2[5];
   partial3[6] = partial2[6];
    
   partial2[0] = h;    //Update partial2 with OLD
   partial2[1] = m2;
   partial2[2] = m1;
   partial2[3] = s2;
   partial2[4] = s1;
   partial2[5] = c2;
   partial2[6] = c1;
  
   while(digitalRead(partial) == LOW) {}; //Debounce, until i press the button i stay here
  } 
}