using System;

public class Program

{

    static double add2numbers(double num1,double num2)//the method for adding 2 numbers

    {

        double total;

        total = num1 + num2;

        return(total);

    }   

    static double subtract2numbers(double num1,double num2)//the method for subtracting 2 numbers

    {

        double total;

        total = num1 - num2;

        return (total);     

    }

    static double multiply2numbers(double num1,double num2)//the method for multiplying 2 numbers

    {

        double total;

        total = num1 * num2;

        return(total);

    }

    static double divide2numbers(double num1,double num2)//the method for division 2 numbers

    {

        double total;

        total = num1 / num2;

        return (total);

    }

    public static void Main()

    {

        string choice;

        double choice1 = 0,num1,num2;

        Console.WriteLine("1. Start calculator\n2. Quit calculator");//user can either quit or use calculator

        Console.Write("\nPlease select what do you want to do : ");

        choice1 = double.Parse(Console.ReadLine());

        while(choice1 !=2)//for looping purposes

        {   

        Console.WriteLine("=============================");

        Console.WriteLine("Welcome to calculator menu");

        Console.WriteLine("A- Addition of 2 numbers\nS- Subtraction of 2 numbers\nM- Multiply by 2 numbers\nD- Division of 2 numbers");//this is the menu

        Console.WriteLine("=============================");

        Console.Write("Please enter your first number : ");//user input 1st number

        num1 = double.Parse(Console.ReadLine());

        Console.Write("Please enter your second number : ");//user input 2nd number

        num2 = double.Parse(Console.ReadLine());

        Console.Write("Please enter your choice : ");

        choice = string.Concat(Console.ReadLine().ToUpper());

        switch (choice)//to choose the action

        {

            case "A":

                Console.Write("Total summation of {0} and {1} is : {2}",num1,num2,add2numbers(num1,num2));

                break;

            case "S":

                Console.Write("Total subtraction of {0} and {1} is : {2}",num1,num2,subtract2numbers(num1,num2));

                break;

            case "M":

                Console.Write("Total multiplication of {0} and {1} is : {2}",num1,num2,multiply2numbers(num1,num2));

                break;

            case "D":

                Console.Write("Total division of {0} and {1} is : {2}",num1,num2,divide2numbers(num1,num2));

                break;

            default:

                Console.WriteLine("That is not a choice, please try again");

                break;

         }      

        Console.WriteLine("\n1. Start calculator\n2. Quit calculator");

        Console.Write("\nPlease select what do you want to do : ");

        choice1 = double.Parse(Console.ReadLine());

        }               

    }

}