Objectives and Grading Lab Objectives: Distinguish between by value, by ref, and

Question

Objectives and Grading
Lab Objectives:

Distinguish between by value, by ref, and out parameter types.
Call class methods using by value, by ref, and out parameters.
Write your own class methods using by value, by ref, and out parameters.
To be able to define and use global named constants
To be able to debug a program of syntax and logic errors
To be able to use the debug step-into feature to step through the logic of the program and to see how the variables change values
Your lab grade will be based upon:

the formatting of your source code;
the use of meaningful identifiers;
the extent of internal documentation; and
the degree to which an exercise's specifications are met.
Preparation:

If you are using the Citrix remote lab, follow the login instructions located in the iLab tab in Course Home.

iLab Steps
Step 1: Requirements - Phone Dialing Program

Your mission: A prepaid phone service needs a program that converts alphanumeric keyboard input into a phone number. The user will input eight characters and the program will output either an error message or the translated seven-digit phone number. The input may contain digits, letters, or both. Letters can be uppercase or lowercase.

The program will perform the conversion per a standard telephone keypad layout.

0
1

2
A B C

3
D E F

4
G H I



5
J K L


6
M N O

7
P Q R S

8
T U V

9
W X Y Z


The program implements the following methods.

Main(): Declares seven character variables and passes these to the following methods by reference:

ProcessInput(): gets user input and performs the conversion

ShowResults(): displays the results
GetInput(): Gets seven characters from the user and stores them into the seven variables Main() has passed by reference.

ProcessInput(): Calls ToDigit() for each, passing each character variable by reference, and returns one of these codes to Main() by value:

0 if there were no input errors

-1 if there were input errors
Input errors include the following:

The first character is 0 (seven-digit phone numbers can't start with 0).

The first three characters are "555" (no phone numbers start with 555).

Any character is not a digit or an uppercase or lowercase letter.
ToDigit(): Converts a character (passed by reference) to its corresponding digit per the table above, and returns one of these codes to ProcessInput() by value:

0 if the character is valid (a digit or uppercase or lowercase letter)

-1 if the character is not valid
ShowResults(): Writes converted telephone number to the screen, inserting a dash (-) between the third and fourth digits, and accepts the seven character variables from Main() by reference.
Sample Output:

Enter a 7 character phone number: 2132121
The converted phone number is: 213-2121

Enter a 7 character phone number: 2scdfER
The converted phone number is: 272-3337

Enter a 7 character phone number: 555resw
Invalid input, please try again.

Enter a 7 character phone number: 0988765
Invalid input, please try again.

Enter a 7 character phone number: 12345678
Invalid input, please try again.

Enter a 7 character phone number: @34*uy
Invalid input, please try again.

Tips

Best practice: Don't try to write too much at a time! First, write an outline in comments based on the requirements and the pseudocode. Then, implement declaring seven char variables. Make sure to fix any compiler errors before implementing more. Then, write and call an empty GetInput() method that accepts parameters, but does nothing but return a dummy value. Make sure you can pass the seven character variables by reference without compiler errors before implementing any of the GetInput() logic. Keep working incrementally like this, testing as you go. Set breakpoints and use the debugger at each phase to make sure your logic is working correctly. Then, use the same approach to implement the other methods. Test each phase with valid input before handling any invalid conditions.

Pseudocode

ProcessInput( ) Method
Get 7 characters from the user and store them in the 7 variables that Main() has passed by reference
Call ToDigit() for each of the 7 characters
If toDigit returns an error code (-1), return an error code (-1)
If the first character is 0, return an error code (-1) to Main()
If the first three characters are 555, return an error code (-1)
If there are no errors, return 0
ToDigit ( ) Method
Convert the characters (passed from ProcessInput() by reference) to upper case
Use a switch statement to translate characters into their corresponding digits.
Write a case statement for each digit and for each valid uppercase letter
Write a default case that returns an error code (-1) for invalid letters
If there are no invalid letters, return 0
ShowResults ( ) Method
Display the Phone Number using the character variables Main() has passed by reference
Main() Method
Declare 7 char variables
Get user input by calling the GetInput() method, passing it the 7 variables by reference
Perform the conversion by calling the ProcessInput( ) method, passing it the 7 variables by reference
Display an error message or call ShowResults(), depending on the code ProcessInput() returns


END

Explanation / Answer

Create a Visual C sharp Console Application using Visual Studio and Save the program as PhoneDialling. Code: using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace PhoneDialling { class Program { static char ToDigit(char testDigit, ref int errorFlag) { testDigit = Char.ToUpper(testDigit); char result; switch (testDigit) { case '0': result = '0'; break; case '1': result = '1'; break; case '2': case 'A': case 'B': case 'C': result = '2'; break; case '3': case 'D': case 'E': case 'F': result = '3'; break; case '4': case 'G': case 'H': case 'I': result = '4'; break; case '5': case 'J': case 'K': case 'L': result = '5'; break; case '6': case 'M': case 'N': case 'O': result = '6'; break; case '7': case 'P': case 'Q': case 'R': case 'S': result = '7'; break; case '8': case 'T': case 'U': case 'V': result = '8'; break; case '9': case 'W': case 'X': case 'Y': case 'Z': result = '9'; break; default: result = 'e'; break; } if (result == 'e') { errorFlag = -1; } else { errorFlag = 0; } //result = testDigit; return result; } static int count555 = 0; static int ReadDials(ref int errorFlag, ref char digit, ref int count) { if ((count == 0 || count == 1 || count == 2) & (digit == '5')) { count555++; if (count555 == 3) errorFlag = -3; return errorFlag; } if ((count == 0) & (digit == 'Q')) { errorFlag = -5; return errorFlag; } else if ((count == 0) & (digit == '0')) { errorFlag = -2; return errorFlag; } else if (count != 8) { digit = ToDigit(digit, ref errorFlag); return errorFlag; } else return errorFlag; } static void Main(string[] args) { char digit1,digit2,digit3,digit4,digit5,digit6,digit7,digit8; string phoneNo; int errorCode = 0, counter = 0; do { counter = 0; Console.Write(" Enter a phone number (Q to quit): "); phoneNo = Console.ReadLine(); if (phoneNo.Equals("Q")) { System.Environment.Exit(0); } if (phoneNo.Length == 7) { phoneNo = phoneNo.Substring(0, 7); digit1 = phoneNo[0]; digit2 = phoneNo[1]; digit3 = phoneNo[2]; digit4 = phoneNo[3]; digit5 = phoneNo[4]; digit6 = phoneNo[5]; digit7 = phoneNo[6]; //digit8 = phoneNo[7]; //Console.WriteLine(digit1); ReadDials(ref errorCode, ref digit1, ref counter); counter++; if (errorCode == 0) ReadDials(ref errorCode, ref digit2, ref counter); counter++; if (errorCode == 0) ReadDials(ref errorCode, ref digit3, ref counter); counter++; if (errorCode == 0) ReadDials(ref errorCode, ref digit4, ref counter); counter++; if (errorCode == 0) ReadDials(ref errorCode, ref digit5, ref counter); counter++; if (errorCode == 0) ReadDials(ref errorCode, ref digit6, ref counter); counter++; if (errorCode == 0) ReadDials(ref errorCode, ref digit7, ref counter); counter++; if (errorCode == 0) Console.WriteLine("Phone Number Dialed: {0}{1}{2}-{3}{4}{5}{6}", digit1, digit2, digit3, digit4, digit5, digit6, digit7); } else { Console.WriteLine("Invalid Phone number (number should be of length 7)"); } switch (errorCode) { case -1: Console.WriteLine("ERROR - An invalid character was entered."); break; case -2: Console.WriteLine("ERROR - Phone number cannot begin with 0."); break; case -3: Console.WriteLine("ERROR - Phone number cannot begin with 555."); break; default: break; } } while (errorCode != -4); } } } Press F5 to run the program.

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