How to program a calcuator in C++

[nicckk]

Have you ever been tired of using a physical calculator, or program your own? This tutorial will help you. (This tut will not teach you how to start programming in C++.)

First setup the preprocesser, the main function,

#include <iostream> 
using namespace std;
int main() 
{

Then define two variables that the user can select. I used a double instead of an int. so the input or output could be a decimal.

    // One and two are the numbers the user selects
     double one, two;

Then we will display two lines of text, along with a "cin" so we can get the users input

    cout << "Please input the first number:";
    cin >> one; // Cin takes the users first number, and associates it to one
    cout << "Please input the second number:";
    cin >> two; // Here cin takes the second number and assigns it to two

Then the math comes into play. In C++ a + sign is used to indicate addition, a - sign for subtraction, a * for multiplication, and a / for division.

    cout << "\nThe answers are:\nAddition:" << one + two; // All the math happens here
    cout << "\nSubtraction:" << one - two;
    cout << "\nMultiplication:" << one * two;
    cout << "\nDivision:" << one / two;
    cout << "\nThank you for using myCalc."; 
    cout << "\n";
    main(); // This starts the main function again, so you can do another calculation

And finally end the main function

    system("PAUSE"); 
    return 0;
}

So in total our code looks like this

#include <iostream> 
using namespace std;
int main() 
{
    // One and two are the numbers the user selects
     double one, two;
    
    cout << "Please input the first number:";
    cin >> one; // Cin takes the users first number, and assosicates it to one
    cout << "Please input the second number:";
    cin >> two; // Here cin takes the second number and assisgns it to two
    cout << "\nThe answers are:\nAddition:" << one + two; // All the math happens here
    cout << "\nSubtraction:" << one - two;
    cout << "\nMultiplication:" << one * two;
    cout << "\nDivision:" << one / two;
    cout << "\nThank you for using myCalc."; 
    cout << "\n";
    main(); // This starts the main function again, so you can do another calculation
    
    system("PAUSE"); 
    return 0;
}

Thanks for reading.

[Jordan]

Very nice tutorial! +rep

[WingedPanther]

It's a nice intro to basic input/output and the operations.

A few observations:
1) you can't pick your operation
2) your program will crash if two == 0.
3) wouldn't a loop be more useful than a recursive call?

[nicckk]

It's a nice intro to basic input/output and the operations.

A few observations:
1) you can't pick your operation
2) your program will crash if two == 0.
3) wouldn't a loop be more useful than a recursive call?

1. I was trying to make the program as simple as possible. If I went to revise it though, I would like to make it so you can select an operation

2. How would this come to be? I ran the program and put 0 in for one and two, and nothing happened to the program.

3. Sure, but once again, I was trying to make it simple. Thank's for your feedback WP, and Jordan.

[WingedPanther]

0/0 is generally not a good idea.

[nicckk]

0/0 is generally not a good idea.

Please input the first number:0
Please input the second number:0

The answers are:
Addition:0
Subtraction:0
Multiplication:0
Division:-1.#IND
Thank you for using myCalc.
Please input the first number:

[WingedPanther]

Interesting... GCC 4.1 gave me "nan" for the output of the division.