Calculator: Code-Along

Start by creating a new .cs file/project. Then, follow the instructions below to create a simple calculator application.

Part 1 - User Input

To begin, the program should ask the user to enter two numbers, and then enter the operation to perform. Assume the user will enter valid integer numbers.

First Number

1. Use Console.WriteLine to ask the user to enter the first number
2. Use Console.ReadLine to receive the input from the user
3. Use Convert.ToInt32 to convert the user's input into an int
4. Make sure to store the result in a variable

Code

Console.WriteLine("Enter a:");
int a = Convert.ToInt32(Console.ReadLine());

Second Number

Repeat the steps for the first number, but store a second int variable for the second number.

Code

Console.WriteLine("Enter b:");
int b = Convert.ToInt32(Console.ReadLine());

Operation

1. Use Console.WriteLine to ask the user for an operation
2. Use Console.ReadLine to receive the input from the user
3. Make sure to restore the result in a string variable

Console.WriteLine("What operation to perform?");
string operation = Console.ReadLine();

Part 2 - Addition

Create a method to add two numbers together, and use it when the user would like to perform the plus operation. Make sure to define the method in the proper place, and call it in the proper place as well.

Defining the Method

Start with the method signature:

• Visibility: public
• Modifier: static
• Return type: int
• Name: AddNumbers
• Parameters: int integer1, int integer2

In the body of the method:

• Add the two ints together
• Return the result

Code

public static int AddNumbers(int integer1, int integer2)
{        
    return integer1 + integer2;
}

Calling the Method

1. In the body of the Main method, after retrieving the input from the user, use an if to check if the user would like to add numbers
2. If the user would like to add numbers, call the AddNumbers method and store the result in a new variable
   • The parameters for the AddNumbers call should be the input from the user (a and b)
3. Print the sum to the console

Code

if (operation == "+")
{
    int sum = AddNumbers(a, b);
    Console.WriteLine(sum);
}

Part 3 - Subtraction

Repeat the steps for the addition method, but use subtraction instead of addition. This should be almost identical, with two key differences: the name of the method should be SubtractNumbers, and the math should use - instead of +.

Final Code

using System;

public class Program
{
    public static void Main()
    {
        Console.WriteLine("Enter a:");
        int a = Convert.ToInt32(Console.ReadLine());

        Console.WriteLine("Enter b:");
        int a = Convert.ToInt32(Console.ReadLine());

        Console.WriteLine("What operation to perform?");
        string operation = Console.ReadLine();

        if (operation == "+")
        {
            int sum = AddNumbers(a, b);
            Console.WriteLine(sum);
        }
        else if (operation == "-")
        {
            int difference = SubtractNumbers(a, b);
            Console.WriteLine(difference);
        }
    }

    public static int AddNumbers(int integer1, int integer2)
    {        
        return integer1 + integer2;
    }

    public static int SubtractNumbers(int integer1, int integer2)
    {        
        return integer1 - integer2;
    }
}