Create a easy calculator

[Bartimäus]

This tutorial will show you how to create an easy calculator in c++!
Its only an easy calculator and it can only calculate two numbers!
This is a Tutorial for beginners who want to learn more about c++.
But its also good to know a bit of c++ to understand the whole code


First we must take an input and some variables to the program :

#include <iostream> //include the standard input and output library 
using namespace std; //includes the standard files
double  number1, number2, result;//these are the variables for the exercise
char character;// this is the char variable for the operation character 

#include <iostream>this includes the iostream library (which contain istream and ostream) that provides input and output functionality.

using namespace std this includes th standard functionality of the c++ libraries. (You can also write std::cout or std::cin)


After that we can programming the main function
First we will ask the user for two numbers.

cout <<"Enter an Exercise ? [+][-][*][/]" << endl; //text output for the user

cout is an Object of class ostream (standard output stream)
with cout and the insertion operator << you bring the text ("Enter an Exercise ? [+][-][*][/]") to the console.



After that we must work with the user input for that we used the command cin and the extraction operator >>(the opposite of <<)

cin  >> number1 >> character >> number2;

cin is an object of istream (standard input stream)
cin and the operator >> transfer the user input to the variables!


Then our program must decide which of the different operations (+-*/) the user had chose. It's possible to do that with an if construction but i think it's
better and more Comfortable to do that with a switch -case construction

switch (character)
{
case '+': 
	result = number1 + number2; 
	break;
case '-':
	result = number1 - number2; 
	break;
case '/':
	result = number1 / number2;  
	break;
case '*': 
	result = number1 * number2; 
	break;
default : 
	cout <<"Error, wrong character !\n"; 
	return 1;  
}

The switch-case construction is like an long if-else construction.

If (character = '+')
{result = number1 + number2; }
else { if (character =='-')
 {result = number1 - number2; 
}}

It's not easy and funny to read such a long if-else code.

switch ( expression )
      case constant-expression : statement
   [default  : statement]

The break after each case is very important it will leave the switch block
Without the program would do all the cases after the right case.
Default :If there is no case match the default will used.
The character for division is / and for multiplication is *.


So, our little calculator is now ready to start.

finally here is the complete code :

int main()
{
cout <<"Enter an Exercise ? [+][-][*][/]" << endl; //text output for the user
cin  >> number1 >> character >> number2;//this will declaring the variables 
//by the user 
switch (character)       //this will decide which operation the user had chose

{
case '+': // if the character is + 
	result = number1 + number2; //this will calculate the result
	break;
case '-': // if the character is -
	result = number1 - number2; //this will calculate the result
	break;
case '/': // if the character is / 
	result = number1 / number2;  //this will calculate the result
	break;
case '*': // if the character is *
	result = number1 * number2; //this will calculate the result
	break;
default : // if the character is wrong
	cout <<"Error, wrong character !\n"; //display the error message
	return 1;  //close the program
}
cout << number1 << character << number2 //display the result for the user
       << "=" << result << endl;//display the result for the user
system("PAUSE");//wait for the user
}

Crash if division by 0 :
If you test the code you will see that it will be cancel when you try to calculate X/0
this is an math error and if you dont want that the program cancel you can add an exception :

case '/': // if the character is / 
	try //this will try to calculate the exercise
	{
	result = number1 / number2;  //this will calculate the result
	throw(1);// if there is any error it will start the exception
	break;
	}
	catch (int a)//this part will treat the error
	{
	
		cout <<"Division by 0"<<endl; //this will display the error
		system("PAUSE); //wait for the user
			return 1; //this close the program
	}

This will try to calculate the result. When you enter a division by 0 the throw will generate a Exception

try 
{   // guarded code}
except ( expression )
{  // exception handler }

Which will treat the error and display an error message to the user.
Then the return 1; will leave the code.


I hope you will enjoy this
Any questions, and positive feedback is welcome!
+rep is appreciated
Sorry for the bad English !

This Tutorial is produced by Bartimäus.

[WingedPanther]

You might want to add exception handling for division by 0.
Could you explain more about what the code does?

[Hoffie]

Thanks good tutorial +rep

[Bartimäus]

You might want to add exception handling for division by 0.
Could you explain more about what the code does?

Thanks for the good idea with division by 0! I would add a try exception to the tut.

[James.H]

Nice tutorial, +rep!

[CommittedC0der]

Nice tut +rep.

[Guest]

So you basically made the C++ version of my calculator.

[whitey6993]

Good tutorial. +rep

[Bartimäus]

So you basically made the C++ version of my calculator.

Yes sorry! I didn't see yours at this time! I think it's already very difficult
to write a beginner tutorial which isn't already in this forum.

[Guest]

Yeah, I was just wondering if you saw mine or not. Also it reminds me I should probably make the more advanced calculator tutorial I had originally planned to do.

Good job on yours though, I definitely like the colors you added.