Else if problem

im having trouble craeting simple calculator can perform 4 basic operations. mistake must  with if-else statements. have 4 conditions addition subtraction multiplication , division, associated 4 letters (a, b, c , d) on keypad in order. if pressed 2 numbers inputed user added if b subtracted , on. (addition) used if , others used else if. , same test (==) all. now, proble, no matter key pressed addition runs. dont know problem might be. thinkin maybe same test cannot ran statements, might right there not meny other tests use [i if (input == 'a') {call addition} , else if (input != a) && (input != a) && (input != a){call subtraction}- == b ==c , == d] still dont understand why cant run same test many times want?

i've been trying figure out past 2 days. appreciated.

thank in advance,

code: [select]

#include <keypad.h>
#include <liquidcrystal.h>

liquidcrystal lcd (7,8,9,10,11,12);



int welcometext(){
lcd.begin(16,2);
  lcd.clear();
  lcd.setcursor(0,0);
  lcd.write("hello");
  delay(2000);
   lcd.clear();
  lcd.setcursor(0,0);
  lcd.write("i calcuator");
  delay(1750);
  lcd.clear();
  delay(1000);
  lcd.begin(16,2);
  lcd.clear();
  lcd.setcursor(0,0);
  lcd.write("press...");
  delay(750);
  lcd.clear();
  lcd.setcursor(0,0);
  lcd.write("'a' add");
  delay(500);
  lcd.clear();
  lcd.setcursor(0,0);
  lcd.write("'b' subtract");
  delay(500);
  lcd.clear();
  lcd.setcursor(0,0);
  lcd.write("'c' multiply");
  delay(500);
  lcd.clear();
  lcd.setcursor(0,0);
  lcd.write("'d' divide");
  delay(500);
  lcd.clear();
  lcd.setcursor(0,0);
  lcd.write("then...");
  delay(500);
  lcd.clear();
  lcd.setcursor(0,0);
  lcd.write("enter 2 numbers");
  delay(600);
 
};

int addition(int x, int y){
  lcd.begin(16,2);
  lcd.clear();
  lcd.setcursor(0,0);
  lcd.print(x, dec);
  lcd.setcursor(2,0);
  lcd.write("+");
  lcd.setcursor(4,0);
  lcd.print(y, dec);
  lcd.setcursor(6,0);
  lcd.write("=");
  int z;
  z = x+y;
lcd.setcursor(8,0);
lcd.print(z,dec);
}





int subtraction (int x, int y){
  lcd.begin(16,2);
  lcd.clear();
  lcd.setcursor(0,0);
  lcd.print(x, dec);
  lcd.setcursor(2,0);
  lcd.write("-");
  lcd.setcursor(4,0);
  lcd.print(y, dec);
  lcd.setcursor(6,0);
  lcd.write("=");
  int z;
  z = x-y;
lcd.setcursor(8,0);
lcd.print(z,dec);
}





int multiplication (int x, int y){
  lcd.begin(16,2);
  lcd.clear();
  lcd.setcursor(0,0);
  lcd.print(x, dec);
  lcd.setcursor(2,0);
  lcd.write("*");
  lcd.setcursor(4,0);
  lcd.print(y, dec);
  lcd.setcursor(6,0);
  lcd.write("=");
  int z;
  z = x*y;
lcd.setcursor(8,0);
lcd.print(z,dec);
}





int division (int x, int y){
  lcd.begin(16,2);
  lcd.clear();
  lcd.setcursor(0,0);
  lcd.print(x, dec);
  lcd.setcursor(2,0);
  lcd.write("/");
  lcd.setcursor(4,0);
  lcd.print(y, dec);
  lcd.setcursor(6,0);
  lcd.write("=");
  int z;
  z = x/y;
lcd.setcursor(8,0);
lcd.print(z,dec);
}














void setup() {

 
    welcometext();
 
}

const byte rows =4;
const byte cols =4;

char keys[rows][cols]={
{1,2,3,'a'},
{4,5,6,'b'},
{7,8,9,'c'},
{'*',0,'#','d'}
};

byte rowpins[rows] = {0,1,2,3};
byte colpins[cols] = {4,5,6,13};

keypad keypad = keypad(makekeymap(keys), rowpins, colpins, rows, cols);
 


void loop(){

 
 
 
 
 
 
  int a;
  int b;
  int operator;

  operator = keypad.getkey();
 


  while (operator != no_key) {
   
   
  if (operator == 'a'){
a = keypad.getkey();
  if (a != no_key){
    {
    b = keypad.getkey();
    }while (b == no_key);
addition(a,b);
delay(100);
  }
  }
   
   
   
     else if (operator == 'b'){
a = keypad.getkey();
  if (a != no_key){
    {
    b = keypad.getkey();
    }while (b == no_key);
subtraction(a,b);
delay(100);
  }
  }
       
       
        else if (operator == 'c'){
a = keypad.getkey();
  if (a != no_key){
    {
    b = keypad.getkey();
    }while (b == no_key);
multiplication(a,b);
delay(100);
  }
  }
 
       
         
      else if (operator == 'd'){
a = keypad.getkey();
  if (a != no_key){
    {
    b = keypad.getkey();
    }while (b == no_key);
division(a,b);
delay(100);
  }
  } 
       
    else{
    lcd.begin(16,2);
  lcd.clear();
  lcd.setcursor(0,0);
  lcd.write("invalid operator");
    }
       
       
       
       
  } 
       
       

}
 

post code here (within code tags), pointing outside discourage many willing help...

check code second if, missing 'b' in code...

code: [select]


     else if (operator == ){


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