// LCD module connections
sbit LCD_RS at PORTA2_bit;
sbit LCD_EN at PORTA3_bit;
sbit LCD_D4 at PORTA4_bit;
sbit LCD_D5 at PORTA5_bit;
sbit LCD_D6 at PORTA6_bit;
sbit LCD_D7 at PORTA7_bit;

sbit LCD_RS_Direction at DDA2_bit;
sbit LCD_EN_Direction at DDA3_bit;
sbit LCD_D4_Direction at DDA4_bit;
sbit LCD_D5_Direction at DDA5_bit;
sbit LCD_D6_Direction at DDA6_bit;
sbit LCD_D7_Direction at DDA7_bit;
// End LCD module connections

int a[3],b[3],g=0,rez=0,r=0,e=0, i=0,j=0,op1,op2;
unsigned rek;
char rezu[8];
void main() {
 DDRD=0;
 DDRC=0;
 DDRB=0;
 Lcd_Init();                        // Initialize LCD
  Lcd_Cmd(_LCD_CLEAR);               // Clear display
  Lcd_Cmd(_LCD_CURSOR_OFF);          // Cursor off
 do{if(PIND==0&&PINC==0&&PINB==0) do{
  if  (PIND4_bit==1) { lcd_out(1,i+1,"0"); a[i]=0; i++;delay_ms(100);break;}
  if  (PIND7_bit==1) { lcd_out(1,i+1,"1"); a[i]=1; i++;delay_ms(100);break;}
  if  (PINC7_bit==1) { lcd_out(1,i+1,"2"); a[i]=2; i++;delay_ms(100);break;}
  if  (PINB7_bit==1) { lcd_out(1,i+1,"3"); a[i]=3; i++;delay_ms(100);break;}
  if  (PIND6_bit==1) { lcd_out(1,i+1,"4"); a[i]=4; i++;delay_ms(100);break;}
  if  (PINC6_bit==1) { lcd_out(1,i+1,"5"); a[i]=5; i++;delay_ms(100);break;}
  if  (PINB6_bit==1) { lcd_out(1,i+1,"6"); a[i]=6; i++;delay_ms(100);break;}
  if  (PIND5_bit==1) { lcd_out(1,i+1,"7"); a[i]=7; i++;delay_ms(100);break;}
  if  (PINC5_bit==1) { lcd_out(1,i+1,"8"); a[i]=8; i++;delay_ms(100);break;}
  if  (PINB5_bit==1) { lcd_out(1,i+1,"9"); a[i]=9; i++;delay_ms(100);break;}
  if  (PINB4_bit==1) {lcd_out(1,i+1,"*"); r=1; g=1;delay_ms(100);break;}
  if  (PINC4_bit==1) {lcd_out(1,i+1,"+"); r=2; g=2;delay_ms(100);break;}
  }while(1); }
  while (r==0);

  do{
  e=0;
  if(PIND==0&&PINC==0&&PINB==0) do{
  if  (PIND4_bit==1) {  lcd_out(2,j+1,"0"); b[j]=0; j++;delay_ms(100);break;}
  if  (PIND7_bit==1) {  lcd_out(2,j+1,"1"); b[j]=1; j++;delay_ms(100);break;}
  if  (PINC7_bit==1) {  lcd_out(2,j+1,"2"); b[j]=2; j++;delay_ms(100);break;}
  if  (PINB7_bit==1) {  lcd_out(2,j+1,"3"); b[j]=3; j++;delay_ms(100);break;}
  if  (PIND6_bit==1) {  lcd_out(2,j+1,"4"); b[j]=4; j++;delay_ms(100);break;}
  if  (PINC6_bit==1) {  lcd_out(2,j+1,"5"); b[j]=5; j++;delay_ms(100);break;}
  if  (PINB6_bit==1) {  lcd_out(2,j+1,"6"); b[j]=6; j++;delay_ms(100);break;}
  if  (PIND5_bit==1) {  lcd_out(2,j+1,"7"); b[j]=7; j++;delay_ms(100);break;}
  if  (PINC5_bit==1) {  lcd_out(2,j+1,"8"); b[j]=8; j++;delay_ms(100);break;}
  if  (PINB5_bit==1) {  lcd_out(2,j+1,"9"); b[j]=9; j++;delay_ms(100);break;}
  if  (PINB3_bit==1) {  lcd_out(2,i+1,"="); e=1;delay_ms(100);break;}
  } while(1); }
  while (e==0);

  if(i==1){op1=a[0];}
  else if(i==2){op1=a[0]*10+a[1];}
  else if(i==3){op1=a[0]*100+a[1]*10+a[2];}


  if(j==1){op2=b[0];}
  else if(j==2){op2=b[0]*10+b[1];}
  else if(j==3){op2=b[0]*100+b[1]*10+b[2];}

  if (g==1){
  rez=op1*op2;
  rek=op1*op2;
  }

  if (g==2)  {
  rez=op1+op2;
  }
  inttostr(rez,rezu);
  if (rek>32767) { lcd_out (2,5,"ERROR");}
    else {lcd_out(2,5,rezu);}
  
 delay_ms(1);
// lcd_out(2,5,rezu);
 delay_ms(1);

 while(1);
}