Write a program that takes a single phone digit. If the digit is a letter, the n

Question

Write a program that takes a single phone digit. If the digit is a letter, the number corresponding to the letter is returned by reference and return 0 by value indicating it is a valid digit. Here are the letters associated with each digit.

0 5 J K L
1 6 M N O
2 A B C 7 P Q R S
3 D E F 8 T U V
4 G H I 9 W X Y Z

If the digit entered is not one of the valid digits or valid letters, return –1 by value indicating that you have an invalid digit.

Sample Output from the Program:
Enter a phone digit (Q to quit): 2
The digit you entered is 2.
Enter a phone digit (Q to quit): F
The digit you entered is 3.
Enter a phone digit (Q to quit): $
The digit you entered is invalid.
Enter a phone digit (Q to quit): -1
The digit you entered is invalid.
Enter a phone digit (Q to quit): Q
Good bye!

Processing Logic:
ToDigit( ) method
Convert the digit to upper case
Use a switch statement to determine if the digit is valid
and convert the letters to digits
If the digit is invalid, return -1.
If the digit is valid, return 0.

Explanation / Answer

using System;

namespace PhoneDigit
{
    class Program
    {
        static void Main(string[] args)
        {
            char digit = '';

            while (Char.ToUpper(digit) != 'Q')
            {
                Console.Write("Enter a phone digit (Q to quit): ");
                digit = Console.ReadLine()[0];

                if (Char.ToUpper(digit) != 'Q')
                {
                    if (ToDigit(ref digit) != -1)
                    {
                        Console.WriteLine("The digit you entered is " + digit);
                    }
                    else
                    {
                        Console.WriteLine("The digit you entered is invalid.");
                    }
                }
            }
            Console.WriteLine("Good bye!");
        }


        public static int ToDigit(ref char chr)
        {
            chr = Char.ToUpper(chr);
            switch (chr)
            {
                case '0':
                case '1':
                case '2':
                case '3':
                case '4':
                case '5':
                case '6':
                case '7':
                case '8':
                case '9':
                    return 0;
                case 'A':
                case 'B':
                case 'C':
                    chr = '2';
                    return 0;
                case 'D':
                case 'E':
                case 'F':
                    chr = '3';
                    return 0;
                case 'G':
                case 'H':
                case 'I':
                    chr = '4';
                    return 0;
                case 'J':
                case 'K':
                case 'L':
                    chr = '5';
                    return 0;
                case 'M':
                case 'N':
                case 'O':
                    chr = '6';
                    return 0;
                case 'P':
                case 'Q':
                case 'R':
                case 'S':
                    chr = '7';
                    return 0;
                case 'T':
                case 'U':
                case 'V':
                    chr = '8';
                    return 0;
                case 'W':
                case 'X':
                case 'Y':
                case 'Z':
                    chr = '9';
                    return 0;
                default:
                    return -1;
            }
         }
    }
}

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