#define Delay 900000
void setup() {
  // put your setup code here, to run once:
  volatile unsigned char *sevenSeg=(unsigned char*)0x30,*keyPad=(unsigned char*)0x27,*digits=(unsigned char*)0x107;

  *sevenSeg=0xFF;
  *keyPad=0x0F;
  *digits=0xFF;

}

boolean read_pad(unsigned char i,unsigned char j){
    volatile unsigned char *padIP=(unsigned char*)0x26,*padOP=(unsigned char*)0x28;
    *padOP=(0x01<<i);
return (((*padIP)&(0x10<<j))>0);
}

unsigned char data_pad(unsigned char row,unsigned char col){
  unsigned char pad[4][4]={
                      {'1','2','3','A'},
                      {'4','5','6','B'},
                      {'7','8','9','C'},
                      {'*','0','#','D'}
                      };
  return pad[row][col];
}
unsigned char readData(){
  volatile unsigned long i;
for(unsigned char i=0;i<4;i++){
  for(unsigned char j=0;j<4;j++){
    if(read_pad(i,j)){
      while(read_pad(i,j));
      return data_pad(i,j);
    }
  }
}
return 0;
}
unsigned char extraChars(unsigned char item){
  switch(item){
    case '-': return 0x40;
    case 'E': return 0x79;
  }
}
unsigned char getValue(unsigned char numb,bool decimal){
  if(numb>9){
    return extraChars(numb);
  }
    unsigned char arr[]={0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F};
  
  if(decimal){
    return arr[numb]|(0x80);
  }else{
    return arr[numb];
  }

}

void dig_write(unsigned char data,unsigned char digNumb){
  volatile unsigned char *seg=(unsigned char*)0x31,*dig=(unsigned char*)0x108;
  *dig=~(0x00);
  *seg=data;
  *dig=~((1<<(digNumb-1)));
  // volatile unsigned long i;
  // for(i=0;i<Delay;i++);
}

void displayError(){
    for(int i=0;i<4;i++){
    dig_write(getValue('E',false),i+1);
  }
}

void allDig(int num){
  unsigned int n;
  bool neg=false;
  if(num>=0){
    n=num;
  }else{
    n=((-1)*num);
    neg=true;
  }
  if(n>9999U){
    displayError();
    return;
  }
  for(int i=0;i<4;i++){
    if((n%10U)>0||i==0)
    {dig_write(getValue((n%10U),false),4-i);
    }else{
      if(neg){
        dig_write(getValue('-',false),4-i);
      }
      break;
    }
    n/=10U;
  }
}

void loop() {
  // put your main code here, to run repeatedly:
  volatile unsigned char *seg=(unsigned char*)0x31,*dig=(unsigned char*)0x108;
   volatile unsigned long i;

//6th use 'B' for subract and '#' for equals
unsigned int temp=0;
unsigned int num1=0,num2=0;
i=0;
unsigned char operation;
while(i<5){
  unsigned char n1=readData();
  if(n1&&((n1-'9')>0||(n1-'0')<0))
  {operation=n1;
    break;}
  if(n1>0){
    temp=temp*10+(n1-'0');
    i++;
  }
}
num1=temp;
temp=0;
i=0;
while(i<5){
  unsigned char n1=readData();
    if(n1=='#')
  break;
  if(n1>0){
    temp=temp*10+(n1-'0');
    i++;
  }
}
num2=temp;


while(readData()!='C'){// to quit use c button

  if(operation=='B')
  allDig((num1-num2));
  else if(operation=='*'){
    allDig((num1*num2));
  }else if(operation=='D'&&num2!=0){
    allDig((num1/num2));
  }else if(operation=='A'&&num2!=0){
    allDig((num1%num2));
  }else{
   displayError();
  }
}
allDig(0U);
}