Arduino - Math Calculator

1#include <LiquidCrystal.h>//including the LCD libary for the project
2#include  <Keypad.h> //including the keypad libary for the project
3
4LiquidCrystal lcd(A0,  A1, A2, A3, A4, A5);
5const byte ROWS = 4; //setting the amount of rows on the  keypad
6const byte COLM = 4; //setting the amount of columns on the keypad
7
8char  keys[ROWS][COLM] = //setting the keys depending on the number of rows and colums
9{
10  {'1', '2', '3', 'A'},
11  {'4', '5', '6', 'B'},
12  {'7', '8', '9', 'C'},
13  {'*', '0', '#', 'D'}
14};
15
16byte rowPins[ROWS] = {13, 12, 11, 10}; //defining  the letters to GPIO pins of Arduino
17byte colmPins[COLM] = {9, 8, 7, 6};
18
19Keypad  keypad = Keypad(makeKeymap(keys), rowPins, colmPins, ROWS, COLM); //compiles all  the arrays to create a keypad object
20
21float inputs[2]; //array used to store  inputs entered by user for two numbers
22bool inputs_entered[2]; //array used for  Arduino to see whether two inputs have been entered
23bool inputs_displayed[2];  //array used to inform Arduino whether the typed information has been printed
24
25char  arithmetic_op; //character datatype used to store input entered by user for operation
26bool  arithmetic_op_entered = false; //boolean datatype used for Arduino to see whether  the input has been entered
27bool arithmetic_op_displayed = false; //boolean datatype  used to inform Arduino whether the typed information has been printed
28
29void  setup() {
30  Serial.begin(9600); //opening the serial communication channel at  baud rate 9600(9600 bits)
31  lcd.begin(16,2); //setting up the LCD's number of  columns and rows
32  
33  lcd.setCursor(0,0);
34  lcd.print("Math calculator");
35  delay(1000);
36  lcd.clear();
37
38  ResetValues(); //function for resetting  value
39  Calculator(); //function for calculating answer and displaying the result
40}
41
42void  loop() {} //void loop is not being used but has to be kept in sketch for....well  reasons
43
44void ResetValues() //function for resetting value
45{
46  for (int  i = 0; i < 2; i++) //for statement that runs whatever in the curly brackets twice;  creates integer variable iteration(i), if (i) is less than 2[do whatever], add 1  to i
47  {
48    inputs_entered[i] = false; //inside the array, depending on the  iteration, change the value(true) to false(as the iteraton increments so does the  value being checked so both values are made false for resetting everything 
49    inputs_displayed[i] = false; //once again(look above) resetting the value
50
51    inputs[i] = 0; //as this is a float, we cannot say false or true so instead  we just set it back to 0 as a way to flush the value
52  }
53
54  arithmetic_op  = NULL; // as it is a charcter, we cannot change the value inside to true or 0,  instead null(in my opinion a form of saying no value, it's undefined, etc)
55  arithmetic_op_entered  = false; //similar to above we are simply resetting the values and whether they  have been entered
56  arithmetic_op_displayed = false; //resetting value
57}
58
59void  Calculator()
60{
61  ResetValues();//function for resetting 
62
63  GetInputs();  //function for getting value from keypad
64  GetOperator();//function for getting  operator value from keypad
65
66  switch (arithmetic_op) { //plugging operator  from GetOperator function via a switch statement to complete functions
67    case  'A':
68      lcd.print(inputs[0] + inputs[1]); 
69      delay(1000);
70      lcd.clear();
71      break;
72    case 'B':
73      lcd.print(inputs[0] - inputs[1]);
74      delay(1000);
75      lcd.clear();
76      break;
77    case 'C':
78      lcd.print(inputs[0]  * inputs[1]);
79      delay(1000);
80      lcd.clear();
81      break;
82    case  'D':
83      lcd.print(inputs[0] / inputs[1]);
84      delay(1000);
85      lcd.clear();
86      break;
87  }
88
89  delay(100); //delay for 100 miliseconds
90  Serial.flush();  //flush potentional values from serial monitor 
91  Calculator(); //calling function  again, [looping]
92}
93
94void GetInputs() //function for getting inputs
95{
96  while (!inputs_entered[0]) { //whilst inputs entered(variable used to store whether  two values have been entered) is false
97    for (int i = 0; i < 2; i++) //looping  contents twice as shown before(you may be asking how we are using the same variable  again, we are not, this is a local variable not global, so we can use the same name  again, further help in comments)
98    {
99      if (!inputs_entered[i] && !inputs_displayed[i])  //if inputs entered and inputs displayed are false
100      {
101        lcd.print("Input  " + String(i) + ": "); //displaying what input it is for the number is via using  the iteration from the for loop
102        inputs_displayed[i] = true; //setting  display value to true, we have completed printing a line of input 1 or 2
103
104        while (!inputs_entered[i]) // if inputs_entered(from the two values inside)  is false, get values
105        {
106          char customKey = keypad.getKey();  //getting value from keypad 
107          if (customKey != NO_KEY) // if there is  a output which is not a blank space(a keypad outputs responses even if there is  no button press, resulting in "empty" values) we get around this via using this  "function"
108          {
109            customKey = convertValues(customKey);  //as the value outputed is a character, in order to do arithmetic calculations,  we must convert it to a integer
110            inputs[i] = customKey; //depending  on what iteration we are on add the corrosponding letter to the inputs array
111            lcd.print(inputs[i]); //printing the value
112            delay(1000);
113            lcd.clear();
114            inputs_entered[i] = true; //in the array  depending on what iteration set the value to true as the process has been completed
115          }
116        }
117      }
118    }
119  }
120}
121
122void GetOperator()//function  for getting operator
123{
124  while (!arithmetic_op_entered) { //process is very  similar to above in getting two values to perform arithmetic operations(if anyone  is confused, don't hesitate to comment)
125    if (!arithmetic_op_entered && !arithmetic_op_displayed)
126    {
127      lcd.print("Operator: ");
128      arithmetic_op_displayed = true;
129
130      while (!arithmetic_op_entered)
131      {
132        char customKey = keypad.getKey();
133        if (customKey != NO_KEY)
134        {
135          arithmetic_op = customKey;
136          lcd.print(keypad.getKey());
137          delay(1000);
138          lcd.clear();
139          arithmetic_op_entered = true;
140        }
141      }
142    }
143  }
144}
145
146int  convertValues(int x) //function used above to convert character value into integer
147{
148  return x - '0'; //returning changed character value now to integer value
149}

1#include <LiquidCrystal.h>//including the LCD libary for the project
2#include   <Keypad.h> //including the keypad libary for the project
3
4LiquidCrystal lcd(A0,   A1, A2, A3, A4, A5);
5const byte ROWS = 4; //setting the amount of rows on the   keypad
6const byte COLM = 4; //setting the amount of columns on the keypad
7
8char   keys[ROWS][COLM] = //setting the keys depending on the number of rows and colums
9{
10   {'1', '2', '3', 'A'},
11  {'4', '5', '6', 'B'},
12  {'7', '8', '9', 'C'},
13   {'*', '0', '#', 'D'}
14};
15
16byte rowPins[ROWS] = {13, 12, 11, 10}; //defining   the letters to GPIO pins of Arduino
17byte colmPins[COLM] = {9, 8, 7, 6};
18
19Keypad   keypad = Keypad(makeKeymap(keys), rowPins, colmPins, ROWS, COLM); //compiles all   the arrays to create a keypad object
20
21float inputs[2]; //array used to store   inputs entered by user for two numbers
22bool inputs_entered[2]; //array used for   Arduino to see whether two inputs have been entered
23bool inputs_displayed[2];   //array used to inform Arduino whether the typed information has been printed
24
25char   arithmetic_op; //character datatype used to store input entered by user for operation
26bool   arithmetic_op_entered = false; //boolean datatype used for Arduino to see whether   the input has been entered
27bool arithmetic_op_displayed = false; //boolean datatype   used to inform Arduino whether the typed information has been printed
28
29void   setup() {
30  Serial.begin(9600); //opening the serial communication channel at   baud rate 9600(9600 bits)
31  lcd.begin(16,2); //setting up the LCD's number of   columns and rows
32  
33  lcd.setCursor(0,0);
34  lcd.print("Math calculator");
35   delay(1000);
36  lcd.clear();
37
38  ResetValues(); //function for resetting   value
39  Calculator(); //function for calculating answer and displaying the result
40}
41
42void   loop() {} //void loop is not being used but has to be kept in sketch for....well   reasons
43
44void ResetValues() //function for resetting value
45{
46  for (int   i = 0; i < 2; i++) //for statement that runs whatever in the curly brackets twice;   creates integer variable iteration(i), if (i) is less than 2[do whatever], add 1   to i
47  {
48    inputs_entered[i] = false; //inside the array, depending on the   iteration, change the value(true) to false(as the iteraton increments so does the   value being checked so both values are made false for resetting everything 
49     inputs_displayed[i] = false; //once again(look above) resetting the value
50
51     inputs[i] = 0; //as this is a float, we cannot say false or true so instead   we just set it back to 0 as a way to flush the value
52  }
53
54  arithmetic_op   = NULL; // as it is a charcter, we cannot change the value inside to true or 0,   instead null(in my opinion a form of saying no value, it's undefined, etc)
55  arithmetic_op_entered   = false; //similar to above we are simply resetting the values and whether they   have been entered
56  arithmetic_op_displayed = false; //resetting value
57}
58
59void   Calculator()
60{
61  ResetValues();//function for resetting 
62
63  GetInputs();   //function for getting value from keypad
64  GetOperator();//function for getting   operator value from keypad
65
66  switch (arithmetic_op) { //plugging operator   from GetOperator function via a switch statement to complete functions
67    case   'A':
68      lcd.print(inputs[0] + inputs[1]); 
69      delay(1000);
70      lcd.clear();
71       break;
72    case 'B':
73      lcd.print(inputs[0] - inputs[1]);
74      delay(1000);
75       lcd.clear();
76      break;
77    case 'C':
78      lcd.print(inputs[0]   * inputs[1]);
79      delay(1000);
80      lcd.clear();
81      break;
82    case   'D':
83      lcd.print(inputs[0] / inputs[1]);
84      delay(1000);
85      lcd.clear();
86       break;
87  }
88
89  delay(100); //delay for 100 miliseconds
90  Serial.flush();   //flush potentional values from serial monitor 
91  Calculator(); //calling function   again, [looping]
92}
93
94void GetInputs() //function for getting inputs
95{
96   while (!inputs_entered[0]) { //whilst inputs entered(variable used to store whether   two values have been entered) is false
97    for (int i = 0; i < 2; i++) //looping   contents twice as shown before(you may be asking how we are using the same variable   again, we are not, this is a local variable not global, so we can use the same name   again, further help in comments)
98    {
99      if (!inputs_entered[i] && !inputs_displayed[i])   //if inputs entered and inputs displayed are false
100      {
101        lcd.print("Input   " + String(i) + ": "); //displaying what input it is for the number is via using   the iteration from the for loop
102        inputs_displayed[i] = true; //setting   display value to true, we have completed printing a line of input 1 or 2
103
104         while (!inputs_entered[i]) // if inputs_entered(from the two values inside)   is false, get values
105        {
106          char customKey = keypad.getKey();   //getting value from keypad 
107          if (customKey != NO_KEY) // if there is   a output which is not a blank space(a keypad outputs responses even if there is   no button press, resulting in "empty" values) we get around this via using this   "function"
108          {
109            customKey = convertValues(customKey);   //as the value outputed is a character, in order to do arithmetic calculations,   we must convert it to a integer
110            inputs[i] = customKey; //depending   on what iteration we are on add the corrosponding letter to the inputs array
111             lcd.print(inputs[i]); //printing the value
112            delay(1000);
113             lcd.clear();
114            inputs_entered[i] = true; //in the array   depending on what iteration set the value to true as the process has been completed
115           }
116        }
117      }
118    }
119  }
120}
121
122void GetOperator()//function   for getting operator
123{
124  while (!arithmetic_op_entered) { //process is very   similar to above in getting two values to perform arithmetic operations(if anyone   is confused, don't hesitate to comment)
125    if (!arithmetic_op_entered && !arithmetic_op_displayed)
126     {
127      lcd.print("Operator: ");
128      arithmetic_op_displayed = true;
129
130       while (!arithmetic_op_entered)
131      {
132        char customKey = keypad.getKey();
133         if (customKey != NO_KEY)
134        {
135          arithmetic_op = customKey;
136           lcd.print(keypad.getKey());
137          delay(1000);
138          lcd.clear();
139           arithmetic_op_entered = true;
140        }
141      }
142    }
143  }
144}
145
146int   convertValues(int x) //function used above to convert character value into integer
147{
148   return x - '0'; //returning changed character value now to integer value
149}

1#include <LiquidCrystal.h>//including the LCD libary for the project
2#include   <Keypad.h> //including the keypad libary for the project
3
4LiquidCrystal lcd(A0,   A1, A2, A3, A4, A5);
5const byte ROWS = 4; //setting the amount of rows on the   keypad
6const byte COLM = 4; //setting the amount of columns on the keypad
7
8char   keys[ROWS][COLM] = //setting the keys depending on the number of rows and colums
9{
10   {'1', '2', '3', 'A'},
11  {'4', '5', '6', 'B'},
12  {'7', '8', '9', 'C'},
13   {'*', '0', '#', 'D'}
14};
15
16byte rowPins[ROWS] = {13, 12, 11, 10}; //defining   the letters to GPIO pins of Arduino
17byte colmPins[COLM] = {9, 8, 7, 6};
18
19Keypad   keypad = Keypad(makeKeymap(keys), rowPins, colmPins, ROWS, COLM); //compiles all   the arrays to create a keypad object
20
21float inputs[2]; //array used to store   inputs entered by user for two numbers
22bool inputs_entered[2]; //array used for   Arduino to see whether two inputs have been entered
23bool inputs_displayed[2];   //array used to inform Arduino whether the typed information has been printed
24
25char   arithmetic_op; //character datatype used to store input entered by user for operation
26bool   arithmetic_op_entered = false; //boolean datatype used for Arduino to see whether   the input has been entered
27bool arithmetic_op_displayed = false; //boolean datatype   used to inform Arduino whether the typed information has been printed
28
29void   setup() {
30  Serial.begin(9600); //opening the serial communication channel at   baud rate 9600(9600 bits)
31  lcd.begin(16,2); //setting up the LCD's number of   columns and rows
32  
33  lcd.setCursor(0,0);
34  lcd.print("Math calculator");
35   delay(1000);
36  lcd.clear();
37
38  ResetValues(); //function for resetting   value
39  Calculator(); //function for calculating answer and displaying the result
40}
41
42void   loop() {} //void loop is not being used but has to be kept in sketch for....well   reasons
43
44void ResetValues() //function for resetting value
45{
46  for (int   i = 0; i < 2; i++) //for statement that runs whatever in the curly brackets twice;   creates integer variable iteration(i), if (i) is less than 2[do whatever], add 1   to i
47  {
48    inputs_entered[i] = false; //inside the array, depending on the   iteration, change the value(true) to false(as the iteraton increments so does the   value being checked so both values are made false for resetting everything 
49     inputs_displayed[i] = false; //once again(look above) resetting the value
50
51     inputs[i] = 0; //as this is a float, we cannot say false or true so instead   we just set it back to 0 as a way to flush the value
52  }
53
54  arithmetic_op   = NULL; // as it is a charcter, we cannot change the value inside to true or 0,   instead null(in my opinion a form of saying no value, it's undefined, etc)
55  arithmetic_op_entered   = false; //similar to above we are simply resetting the values and whether they   have been entered
56  arithmetic_op_displayed = false; //resetting value
57}
58
59void   Calculator()
60{
61  ResetValues();//function for resetting 
62
63  GetInputs();   //function for getting value from keypad
64  GetOperator();//function for getting   operator value from keypad
65
66  switch (arithmetic_op) { //plugging operator   from GetOperator function via a switch statement to complete functions
67    case   'A':
68      lcd.print(inputs[0] + inputs[1]); 
69      delay(1000);
70      lcd.clear();
71       break;
72    case 'B':
73      lcd.print(inputs[0] - inputs[1]);
74      delay(1000);
75       lcd.clear();
76      break;
77    case 'C':
78      lcd.print(inputs[0]   * inputs[1]);
79      delay(1000);
80      lcd.clear();
81      break;
82    case   'D':
83      lcd.print(inputs[0] / inputs[1]);
84      delay(1000);
85      lcd.clear();
86       break;
87  }
88
89  delay(100); //delay for 100 miliseconds
90  Serial.flush();   //flush potentional values from serial monitor 
91  Calculator(); //calling function   again, [looping]
92}
93
94void GetInputs() //function for getting inputs
95{
96   while (!inputs_entered[0]) { //whilst inputs entered(variable used to store whether   two values have been entered) is false
97    for (int i = 0; i < 2; i++) //looping   contents twice as shown before(you may be asking how we are using the same variable   again, we are not, this is a local variable not global, so we can use the same name   again, further help in comments)
98    {
99      if (!inputs_entered[i] && !inputs_displayed[i])   //if inputs entered and inputs displayed are false
100      {
101        lcd.print("Input   " + String(i) + ": "); //displaying what input it is for the number is via using   the iteration from the for loop
102        inputs_displayed[i] = true; //setting   display value to true, we have completed printing a line of input 1 or 2
103
104         while (!inputs_entered[i]) // if inputs_entered(from the two values inside)   is false, get values
105        {
106          char customKey = keypad.getKey();   //getting value from keypad 
107          if (customKey != NO_KEY) // if there is   a output which is not a blank space(a keypad outputs responses even if there is   no button press, resulting in "empty" values) we get around this via using this   "function"
108          {
109            customKey = convertValues(customKey);   //as the value outputed is a character, in order to do arithmetic calculations,   we must convert it to a integer
110            inputs[i] = customKey; //depending   on what iteration we are on add the corrosponding letter to the inputs array
111             lcd.print(inputs[i]); //printing the value
112            delay(1000);
113             lcd.clear();
114            inputs_entered[i] = true; //in the array   depending on what iteration set the value to true as the process has been completed
115           }
116        }
117      }
118    }
119  }
120}
121
122void GetOperator()//function   for getting operator
123{
124  while (!arithmetic_op_entered) { //process is very   similar to above in getting two values to perform arithmetic operations(if anyone   is confused, don't hesitate to comment)
125    if (!arithmetic_op_entered && !arithmetic_op_displayed)
126     {
127      lcd.print("Operator: ");
128      arithmetic_op_displayed = true;
129
130       while (!arithmetic_op_entered)
131      {
132        char customKey = keypad.getKey();
133         if (customKey != NO_KEY)
134        {
135          arithmetic_op = customKey;
136           lcd.print(keypad.getKey());
137          delay(1000);
138          lcd.clear();
139           arithmetic_op_entered = true;
140        }
141      }
142    }
143  }
144}
145
146int   convertValues(int x) //function used above to convert character value into integer
147{
148   return x - '0'; //returning changed character value now to integer value
149}

1#include <LiquidCrystal.h>//including the LCD libary for the project
2#include
3  <Keypad.h> //including the keypad libary for the project
4
5LiquidCrystal lcd(A0,
6  A1, A2, A3, A4, A5);
7const byte ROWS = 4; //setting the amount of rows on the
8  keypad
9const byte COLM = 4; //setting the amount of columns on the keypad
10
11char
12  keys[ROWS][COLM] = //setting the keys depending on the number of rows and colums
13{
14
15  {'1', '2', '3', 'A'},
16  {'4', '5', '6', 'B'},
17  {'7', '8', '9', 'C'},
18
19  {'*', '0', '#', 'D'}
20};
21
22byte rowPins[ROWS] = {13, 12, 11, 10}; //defining
23  the letters to GPIO pins of Arduino
24byte colmPins[COLM] = {9, 8, 7, 6};
25
26Keypad
27  keypad = Keypad(makeKeymap(keys), rowPins, colmPins, ROWS, COLM); //compiles all
28  the arrays to create a keypad object
29
30float inputs[2]; //array used to store
31  inputs entered by user for two numbers
32bool inputs_entered[2]; //array used for
33  Arduino to see whether two inputs have been entered
34bool inputs_displayed[2];
35  //array used to inform Arduino whether the typed information has been printed
36
37char
38  arithmetic_op; //character datatype used to store input entered by user for operation
39bool
40  arithmetic_op_entered = false; //boolean datatype used for Arduino to see whether
41  the input has been entered
42bool arithmetic_op_displayed = false; //boolean datatype
43  used to inform Arduino whether the typed information has been printed
44
45void
46  setup() {
47  Serial.begin(9600); //opening the serial communication channel at
48  baud rate 9600(9600 bits)
49  lcd.begin(16,2); //setting up the LCD's number of
50  columns and rows
51  
52  lcd.setCursor(0,0);
53  lcd.print("Math calculator");
54
55  delay(1000);
56  lcd.clear();
57
58  ResetValues(); //function for resetting
59  value
60  Calculator(); //function for calculating answer and displaying the result
61}
62
63void
64  loop() {} //void loop is not being used but has to be kept in sketch for....well
65  reasons
66
67void ResetValues() //function for resetting value
68{
69  for (int
70  i = 0; i < 2; i++) //for statement that runs whatever in the curly brackets twice;
71  creates integer variable iteration(i), if (i) is less than 2[do whatever], add 1
72  to i
73  {
74    inputs_entered[i] = false; //inside the array, depending on the
75  iteration, change the value(true) to false(as the iteraton increments so does the
76  value being checked so both values are made false for resetting everything 
77
78    inputs_displayed[i] = false; //once again(look above) resetting the value
79
80
81    inputs[i] = 0; //as this is a float, we cannot say false or true so instead
82  we just set it back to 0 as a way to flush the value
83  }
84
85  arithmetic_op
86  = NULL; // as it is a charcter, we cannot change the value inside to true or 0,
87  instead null(in my opinion a form of saying no value, it's undefined, etc)
88  arithmetic_op_entered
89  = false; //similar to above we are simply resetting the values and whether they
90  have been entered
91  arithmetic_op_displayed = false; //resetting value
92}
93
94void
95  Calculator()
96{
97  ResetValues();//function for resetting 
98
99  GetInputs();
100  //function for getting value from keypad
101  GetOperator();//function for getting
102  operator value from keypad
103
104  switch (arithmetic_op) { //plugging operator
105  from GetOperator function via a switch statement to complete functions
106    case
107  'A':
108      lcd.print(inputs[0] + inputs[1]); 
109      delay(1000);
110      lcd.clear();
111
112      break;
113    case 'B':
114      lcd.print(inputs[0] - inputs[1]);
115      delay(1000);
116
117      lcd.clear();
118      break;
119    case 'C':
120      lcd.print(inputs[0]
121  * inputs[1]);
122      delay(1000);
123      lcd.clear();
124      break;
125    case
126  'D':
127      lcd.print(inputs[0] / inputs[1]);
128      delay(1000);
129      lcd.clear();
130
131      break;
132  }
133
134  delay(100); //delay for 100 miliseconds
135  Serial.flush();
136  //flush potentional values from serial monitor 
137  Calculator(); //calling function
138  again, [looping]
139}
140
141void GetInputs() //function for getting inputs
142{
143
144  while (!inputs_entered[0]) { //whilst inputs entered(variable used to store whether
145  two values have been entered) is false
146    for (int i = 0; i < 2; i++) //looping
147  contents twice as shown before(you may be asking how we are using the same variable
148  again, we are not, this is a local variable not global, so we can use the same name
149  again, further help in comments)
150    {
151      if (!inputs_entered[i] && !inputs_displayed[i])
152  //if inputs entered and inputs displayed are false
153      {
154        lcd.print("Input
155  " + String(i) + ": "); //displaying what input it is for the number is via using
156  the iteration from the for loop
157        inputs_displayed[i] = true; //setting
158  display value to true, we have completed printing a line of input 1 or 2
159
160
161        while (!inputs_entered[i]) // if inputs_entered(from the two values inside)
162  is false, get values
163        {
164          char customKey = keypad.getKey();
165  //getting value from keypad 
166          if (customKey != NO_KEY) // if there is
167  a output which is not a blank space(a keypad outputs responses even if there is
168  no button press, resulting in "empty" values) we get around this via using this
169  "function"
170          {
171            customKey = convertValues(customKey);
172  //as the value outputed is a character, in order to do arithmetic calculations,
173  we must convert it to a integer
174            inputs[i] = customKey; //depending
175  on what iteration we are on add the corrosponding letter to the inputs array
176
177            lcd.print(inputs[i]); //printing the value
178            delay(1000);
179
180            lcd.clear();
181            inputs_entered[i] = true; //in the array
182  depending on what iteration set the value to true as the process has been completed
183
184          }
185        }
186      }
187    }
188  }
189}
190
191void GetOperator()//function
192  for getting operator
193{
194  while (!arithmetic_op_entered) { //process is very
195  similar to above in getting two values to perform arithmetic operations(if anyone
196  is confused, don't hesitate to comment)
197    if (!arithmetic_op_entered && !arithmetic_op_displayed)
198
199    {
200      lcd.print("Operator: ");
201      arithmetic_op_displayed = true;
202
203
204      while (!arithmetic_op_entered)
205      {
206        char customKey = keypad.getKey();
207
208        if (customKey != NO_KEY)
209        {
210          arithmetic_op = customKey;
211
212          lcd.print(keypad.getKey());
213          delay(1000);
214          lcd.clear();
215
216          arithmetic_op_entered = true;
217        }
218      }
219    }
220  }
221}
222
223int
224  convertValues(int x) //function used above to convert character value into integer
225{
226
227  return x - '0'; //returning changed character value now to integer value
228}

1#include <LiquidCrystal.h>//including the LCD libary for the project
2#include  <Keypad.h> //including the keypad libary for the project
3
4LiquidCrystal lcd(A0,  A1, A2, A3, A4, A5);
5const byte ROWS = 4; //setting the amount of rows on the  keypad
6const byte COLM = 4; //setting the amount of columns on the keypad
7
8char  keys[ROWS][COLM] = //setting the keys depending on the number of rows and colums
9{
10  {'1', '2', '3', 'A'},
11  {'4', '5', '6', 'B'},
12  {'7', '8', '9', 'C'},
13  {'*', '0', '#', 'D'}
14};
15
16byte rowPins[ROWS] = {13, 12, 11, 10}; //defining  the letters to GPIO pins of Arduino
17byte colmPins[COLM] = {9, 8, 7, 6};
18
19Keypad  keypad = Keypad(makeKeymap(keys), rowPins, colmPins, ROWS, COLM); //compiles all  the arrays to create a keypad object
20
21float inputs[2]; //array used to store  inputs entered by user for two numbers
22bool inputs_entered[2]; //array used for  Arduino to see whether two inputs have been entered
23bool inputs_displayed[2];  //array used to inform Arduino whether the typed information has been printed
24
25char  arithmetic_op; //character datatype used to store input entered by user for operation
26bool  arithmetic_op_entered = false; //boolean datatype used for Arduino to see whether  the input has been entered
27bool arithmetic_op_displayed = false; //boolean datatype  used to inform Arduino whether the typed information has been printed
28
29void  setup() {
30  Serial.begin(9600); //opening the serial communication channel at  baud rate 9600(9600 bits)
31  lcd.begin(16,2); //setting up the LCD's number of  columns and rows
32  
33  lcd.setCursor(0,0);
34  lcd.print("Math calculator");
35  delay(1000);
36  lcd.clear();
37
38  ResetValues(); //function for resetting  value
39  Calculator(); //function for calculating answer and displaying the result
40}
41
42void  loop() {} //void loop is not being used but has to be kept in sketch for....well  reasons
43
44void ResetValues() //function for resetting value
45{
46  for (int  i = 0; i < 2; i++) //for statement that runs whatever in the curly brackets twice;  creates integer variable iteration(i), if (i) is less than 2[do whatever], add 1  to i
47  {
48    inputs_entered[i] = false; //inside the array, depending on the  iteration, change the value(true) to false(as the iteraton increments so does the  value being checked so both values are made false for resetting everything 
49    inputs_displayed[i] = false; //once again(look above) resetting the value
50
51    inputs[i] = 0; //as this is a float, we cannot say false or true so instead  we just set it back to 0 as a way to flush the value
52  }
53
54  arithmetic_op  = NULL; // as it is a charcter, we cannot change the value inside to true or 0,  instead null(in my opinion a form of saying no value, it's undefined, etc)
55  arithmetic_op_entered  = false; //similar to above we are simply resetting the values and whether they  have been entered
56  arithmetic_op_displayed = false; //resetting value
57}
58
59void  Calculator()
60{
61  ResetValues();//function for resetting 
62
63  GetInputs();  //function for getting value from keypad
64  GetOperator();//function for getting  operator value from keypad
65
66  switch (arithmetic_op) { //plugging operator  from GetOperator function via a switch statement to complete functions
67    case  'A':
68      lcd.print(inputs[0] + inputs[1]); 
69      delay(1000);
70      lcd.clear();
71      break;
72    case 'B':
73      lcd.print(inputs[0] - inputs[1]);
74      delay(1000);
75      lcd.clear();
76      break;
77    case 'C':
78      lcd.print(inputs[0]  * inputs[1]);
79      delay(1000);
80      lcd.clear();
81      break;
82    case  'D':
83      lcd.print(inputs[0] / inputs[1]);
84      delay(1000);
85      lcd.clear();
86      break;
87  }
88
89  delay(100); //delay for 100 miliseconds
90  Serial.flush();  //flush potentional values from serial monitor 
91  Calculator(); //calling function  again, [looping]
92}
93
94void GetInputs() //function for getting inputs
95{
96  while (!inputs_entered[0]) { //whilst inputs entered(variable used to store whether  two values have been entered) is false
97    for (int i = 0; i < 2; i++) //looping  contents twice as shown before(you may be asking how we are using the same variable  again, we are not, this is a local variable not global, so we can use the same name  again, further help in comments)
98    {
99      if (!inputs_entered[i] && !inputs_displayed[i])  //if inputs entered and inputs displayed are false
100      {
101        lcd.print("Input  " + String(i) + ": "); //displaying what input it is for the number is via using  the iteration from the for loop
102        inputs_displayed[i] = true; //setting  display value to true, we have completed printing a line of input 1 or 2
103
104        while (!inputs_entered[i]) // if inputs_entered(from the two values inside)  is false, get values
105        {
106          char customKey = keypad.getKey();  //getting value from keypad 
107          if (customKey != NO_KEY) // if there is  a output which is not a blank space(a keypad outputs responses even if there is  no button press, resulting in "empty" values) we get around this via using this  "function"
108          {
109            customKey = convertValues(customKey);  //as the value outputed is a character, in order to do arithmetic calculations,  we must convert it to a integer
110            inputs[i] = customKey; //depending  on what iteration we are on add the corrosponding letter to the inputs array
111            lcd.print(inputs[i]); //printing the value
112            delay(1000);
113            lcd.clear();
114            inputs_entered[i] = true; //in the array  depending on what iteration set the value to true as the process has been completed
115          }
116        }
117      }
118    }
119  }
120}
121
122void GetOperator()//function  for getting operator
123{
124  while (!arithmetic_op_entered) { //process is very  similar to above in getting two values to perform arithmetic operations(if anyone  is confused, don't hesitate to comment)
125    if (!arithmetic_op_entered && !arithmetic_op_displayed)
126    {
127      lcd.print("Operator: ");
128      arithmetic_op_displayed = true;
129
130      while (!arithmetic_op_entered)
131      {
132        char customKey = keypad.getKey();
133        if (customKey != NO_KEY)
134        {
135          arithmetic_op = customKey;
136          lcd.print(keypad.getKey());
137          delay(1000);
138          lcd.clear();
139          arithmetic_op_entered = true;
140        }
141      }
142    }
143  }
144}
145
146int  convertValues(int x) //function used above to convert character value into integer
147{
148  return x - '0'; //returning changed character value now to integer value
149}