help with basic c++ function homework problem

Write a program that simulates the dial of a phone number. The program will input a phone number and the program will acknowledge the call by either writing an error message or the 8 digit phone number to the console window. The phone number may have either digits, letters, or both. 

Define a function named ReadDials() that reads each digit/letter dialed into 8 separate char variables (DO NOT USE ARRAYS). All digits are sent back through parameters by reference.  Then, for each digit, the program will use a function named ToDigit(), which receives a single char argument (pass by reference) that may be a number or a letter of one of the digits dialed. If it is a number, return 0 by value indicating it is a valid 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.

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.

A phone number never begins with a 0, so the program should flag an error if such a number is entered. Make ReadDials() return –2 in this case.  Also a phone number never begins with 555, so the program should flag an error if such a number is entered. Make ReadDials() return –3 in this case.  A phone number always has a hyphen (-) in the 4th position. Make ReadDials() return –4 if it doesn't have a hyphen in the 4th position. If a hyphen is in any other position, it is considered an invalid digit. If the phone number is valid, main calls the AcknowledgeCall function to write the converted number to the output file.

All the logic of the program should be put in functions that are called from Main(): ReadDials(), and AcknowledgeCall().  The ToDigits() function is called from the ReadDials() function and is used to convert each letter entered individually to a digit and to verify the user has entered a valid phone number. Have the program work for any number of phone numbers.  Continue processing until the user enters a Q.

In the ToDigits() function use the toupperfunction to convert any letters entered to uppercase. All error messages are to be written to the output file from main() based on the return value from the functions.

You will set up the 8 char variables to hold the digits of the phone number in main() and pass the variables to the functions by reference.

Sample Output from the Program:

Enter a phone number (Q to quit): 213-2121

Phone Number Dialed: 213-2121

Enter a phone number (Q to quit): asc-dfer

Phone Number Dialed: 272-3337

Enter a phone number (Q to quit): 555-resw

ERROR - Phone number cannot begin with 555

Enter a phone number (Q to quit): 098-8765

ERROR - Phone number cannot begin with 0

Enter a phone number (Q to quit): 12345678

ERROR - Hyphen is not in the correct position

Enter a phone number (Q to quit): @34-*uyt

ERROR - An invalid character was entered

Enter a phone number (Q to quit): Q

Press any key to continue . . .

Step 2: Processing Logic

Using the pseudo code below, write the code that will meet the requirements:

Main Function
    Declare the char variables for the 8 digits of the phone number

    while true
        Call the ReadDials function passing the 8 digits
        by reference.  ReadDials returns an error code by
        value.

        If the return value is -5, exit the do while loop

        If the error code is -1, display the
          error message "ERROR - An invalid character was entered".
        If the error code is -2, display the
          error message "ERROR - Phone number cannot begin with 0".
        If the error code is -3, display the
          error message "ERROR - Phone number cannot begin with 555".
        If the error code is -4, display the
          error message "ERROR - Hyphen is not in the correct position".
        Otherwise, call the AcknowledgeCall function
    End-While

ReadDials function

    Input the first digit
    If a Q was entered, return -5.
    Input the rest of the phone number

    Call the ToDigit function for each of the 7 digits
      not for digit 4
    If ToDigit returns -1, return -1
    If digit 4 is not a hyphen, return -4.
    If digit 1 is 0, return -2.
    If digits 1 - 3 are 5, return -3
    Otherwise, return 0

ToDigit function
    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.

AcknowledgeCall function
    Display the Phone Number.