Simple UNO calculator

1/* Serial arduino calculator
2in this project, you can make basic
3arithmetic  with the help of arduino,
4almost like a very rustic calculator.
5It accepts  two numbers and a signal, and
6makes the operation, witch can be of +, -, * or  /.
7E.G. : send "2+3" (Without quotes and with no
8space separing the info),  and arduino answers 5.
9Digit "7-3" and arduino te responde com 4.
10Criado  por João Paulo Rodrigues Poltronieri
11
12This code is on public domain
13*/
14
15//  first of all, create variables to store
16// the information sent to arduino
17
18lng  number1; // first number of the calculation,
19// sent through the Serial monitor
20
21//  If you take a look, it's a long varible, so
22// we're able to use big numbers
23
24long  number2; // second number sent through the SM
25
26char calSignal; // create a  char variable to store
27// the calcuation signal.
28
29long result; // result  of the calculation
30
31void setup() {
32  Serial.begin(9600); // begins serial  communications
33  Serial.println("Send me a calculation"); 
34  Serial.println("E.G.  : 2+3");
35  Serial.println();
36  // prints this to test serial communication,  and
37  // prints a line space
38}
39
40void loop() {
41  while(Serial.available()  > 0) {
42    // while there are dada being sent to arduino,
43    
44    number1  = Serial.parseInt();
45    // number1 will be the first number
46    
47    //  Note the use of "Serial.parseInt, so,
48    // in case you use 23, it stores in  
49    // number1 the number 23
50    
51    // if we used Serial.read(), it  would
52    // only store 2
53    
54    calSignal = Serial.read(); // calSignal  will be the first
55    // info after the first number
56    
57    number2 =  Serial.parseInt(); // stores the second
58    // number in number2
59    
60    resolucao(); // Custom function to solve the calculations
61 
62    Serial.println("Resultado  = ");
63    Serial.println(result);
64    // Prints the result of the calculation
65    Serial.println(); // jumps a line
66    Serial.println("Outra conta, por favor");  // prints
67    Serial.println(); // jumps a line
68  }
69}
70
71void resolucao()  { // Custom function that
72  // solves the calculations
73  
74  switch (calSignal)  {
75    // Here we use "switch...case" to save some space on
76    // the sketch.  It's, basicaly, a function that verifies
77    // various "if" statements.
78    
79    // Here, it verifies what's the value held by 
80    // calSigna. Basicaly,  it verifies the "signal"
81    // of the calculation
82    
83    case '+'  : // if calSignal is '+'
84    result = number1 + number2; // sums the numbers
85    // and makes result hold the value of the calculation
86    break; // break  to exit the "case"
87    case '+' : // if calSignal is '+'
88    result = number1  - number2; // subtracts the numbers
89    // and makes result hold the value of  the calculation
90    break; // break to exit the "case"
91    case '+' : //  if calSignal is '+'
92    result = number1 * number2; // multiplies the numbers
93    // and makes result hold the value of the calculation
94    break; // break  to exit the "case"
95    case '/' : // se calSignal for '/'
96    result = number1  / number2; // divides the numbers
97    // and makes result hold the value of the  calculation
98    // PS: in case the division isn't exact, the result 
99    //  will be the nearest integrer
100    break; // break to exit the "case"
101    default  : // If it's not any of these...
102    Serial.println("CONTA INVÁVIDA");
103    // Creates an "error"
104    Serial.println();
105    resultado = 0;
106  }
107}