Arduino Calculator with Lcd I2C

1#include <LiquidCrystal_I2C.h> 
2#include <Keypad.h> //Header file for  Keypad from https://github.com/Chris--A/Keypad
3
4const byte ROWS = 4; // Four  rows
5const byte COLS = 4; // Four columns
6
7// Define the Keymap
8char  keys[ROWS][COLS] = {
9
10  {'1','2','3','A'},
11
12  {'4','5','6','B'},
13
14  {'7','8','9','C'},
15
16  {'*','0','#','D'}
17
18};
19
20byte rowPins[ROWS]  = { 0, 1, 2, 3 };// Connect keypad ROW0, ROW1, ROW2 and ROW3 to these Arduino pins.
21byte  colPins[COLS] = { 4, 5, 6, 7 }; // Connect keypad COL0, COL1 and COL2 to these Arduino  pins.
22
23Keypad kpd = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS  ); //  Create the Keypad
24
25const int rs = 8, en = 9, d4 = 10, d5 = 11, d6 =  12, d7 = 13; //Pins to which LCD is connected
26LiquidCrystal_I2C lcd(0x27, 16,  2);
27
28 long Num1,Num2,Number;
29 char key,action;
30 boolean result = false;
31  
32void setup() {
33  lcd.begin(); //We are using a 16*2 LCD display
34  lcd.print("Calculator  Ready"); //Display a intro message
35  lcd.setCursor(0, 1);   // set the cursor  to column 0, line 1
36  lcd.print("A=+ B=- C=* D=/"); //Display a intro message  
37
38   delay(6000); //Wait for display to show info
39    lcd.clear(); //Then  clean it
40}
41
42void loop() {
43  
44key = kpd.getKey(); //storing pressed  key value in a char
45
46if (key!=NO_KEY)
47DetectButtons();
48
49if (result==true)
50CalculateResult();
51
52DisplayResult();   
53}
54
55void DetectButtons()
56{ 
57     lcd.clear(); //Then clean it
58    if (key=='*') //If cancel Button is pressed
59    {Serial.println ("Button  Cancel"); Number=Num1=Num2=0; result=false;}
60    
61     if (key == '1') //If  Button 1 is pressed
62    {Serial.println ("Button 1"); 
63    if (Number==0)
64    Number=1;
65    else
66    Number = (Number*10) + 1; //Pressed twice
67    }
68    
69     if (key == '4') //If Button 4 is pressed
70    {Serial.println ("Button  4"); 
71    if (Number==0)
72    Number=4;
73    else
74    Number = (Number*10)  + 4; //Pressed twice
75    }
76    
77     if (key == '7') //If Button 7 is pressed
78    {Serial.println ("Button 7");
79    if (Number==0)
80    Number=7;
81    else
82    Number = (Number*10) + 7; //Pressed twice
83    } 
84  
85
86    if (key  == '0')
87    {Serial.println ("Button 0"); //Button 0 is Pressed
88    if (Number==0)
89    Number=0;
90    else
91    Number = (Number*10) + 0; //Pressed twice
92    }
93    
94     if (key == '2') //Button 2 is Pressed
95    {Serial.println ("Button  2"); 
96     if (Number==0)
97    Number=2;
98    else
99    Number = (Number*10)  + 2; //Pressed twice
100    }
101    
102     if (key == '5')
103    {Serial.println  ("Button 5"); 
104     if (Number==0)
105    Number=5;
106    else
107    Number  = (Number*10) + 5; //Pressed twice
108    }
109    
110     if (key == '8')
111    {Serial.println ("Button 8"); 
112     if (Number==0)
113    Number=8;
114    else
115    Number = (Number*10) + 8; //Pressed twice
116    }   
117  
118
119    if (key == '#')
120    {Serial.println ("Button Equal"); 
121    Num2=Number;
122    result = true;
123    }
124    
125     if (key == '3')
126    {Serial.println  ("Button 3"); 
127     if (Number==0)
128    Number=3;
129    else
130    Number  = (Number*10) + 3; //Pressed twice
131    }
132    
133     if (key == '6')
134    {Serial.println ("Button 6"); 
135    if (Number==0)
136    Number=6;
137    else
138    Number = (Number*10) + 6; //Pressed twice
139    }
140    
141     if  (key == '9')
142    {Serial.println ("Button 9");
143    if (Number==0)
144    Number=9;
145    else
146    Number = (Number*10) + 9; //Pressed twice
147    }  
148
149      if  (key == 'A' || key == 'B' || key == 'C' || key == 'D') //Detecting Buttons on Column  4
150  {
151    Num1 = Number;    
152    Number =0;
153    if (key == 'A')
154    {Serial.println ("Addition"); action = '+';}
155     if (key == 'B')
156    {Serial.println  ("Subtraction"); action = '-'; }
157     if (key == 'C')
158    {Serial.println  ("Multiplication"); action = '*';}
159     if (key == 'D')
160    {Serial.println  ("Division"); action = '/';}  
161
162    delay(100);
163  }
164  
165}
166
167void  CalculateResult()
168{
169  if (action=='+')
170    Number = Num1+Num2;
171
172  if (action=='-')
173    Number = Num1-Num2;
174
175  if (action=='*')
176    Number  = Num1*Num2;
177
178  if (action=='/')
179    Number = Num1/Num2; 
180}
181
182void  DisplayResult()
183{
184  lcd.setCursor(0, 0);   // set the cursor to column 0,  line 1
185  lcd.print(Num1); lcd.print(action); lcd.print(Num2); 
186  
187  if  (result==true)
188  {lcd.print(" ="); lcd.print(Number);} //Display the result
189  
190  lcd.setCursor(0, 1);   // set the cursor to column 0, line 1
191  lcd.print(Number);  //Display the result
192}
193