C# Passing reference parameter to array

First of all I would create a separate class for storing your phones data:

public class Phone
{
    public string Manufacturer { get; set; }
    public string Model { get; set; }
    public bool HasCord { get; set; }
    public double Price { get; set: }
}

Then instead of:

static void inputPhone(ref string manufacturer, ref string model, ref bool hasCord, ref double price)

You could have:

static Phone GetPhone()

And you could create an instance of a Phone inside GetPhone method and return the object that is filled in with appropriate data.

Instead of:

double[] prices = new double[100];
string[] manufacturers = new string[100];
string[] models = new string[100];
bool[] hasCords = new bool[100];

You could then have:

List<Phone> phones = new List<Phone>(); 

And then after each call to GetInput (previously: inputPhone) add it to the list:

phones.Add(GetPhone()); 

Then change the outputPhones to:

static void DisplayPhones(List<Phone> phones)

So all in all your code would look like this:

static Phone GetPhone()
{
    Phone phone = new Phone(); 
    Console.Write("Enter the phone manufacturer: ");
    phone.Manufacturer = Console.ReadLine();
    Console.Write("Enter the phone model: ");
    phone.Model = Console.ReadLine();
    Console.Write("Is it cordless? [Y or N]: ");
    phone.HasCord = Console.ReadLine().ToUpper() == "Y";
    Console.Write("Enter the phone price: ");
    phone.Price = Convert.ToDouble(Console.ReadLine());
    return phone; 
}

static void DisplayPhones(List<Phone> phones)
{
    for (int i = 0; i < phones.Count; i++)
    {
        Console.WriteLine("==Phone #{0}==", i);
        Console.WriteLine("Phone Manufacturer: {0}", phones[i].Manufacturer);
        Console.WriteLine("Phone Model: {0}", phones[i].Model);
        Console.WriteLine("Has Cord: {0}", phones[i].HasCord ? "Yes" : "No");
        Console.WriteLine("Phone Price: {0}", phones[i].Price);
    }
    Console.WriteLine("Number of phones entered: {0}", phones.Count);
}

static void Main(string[] args)
{
    List<Phone> phones = new List<Phone>(); 
    bool shouldContinue = true;

    do
    {
        phones.Add(GetPhone());
        Console.Write("Would like to process another phone? [Y or N]: ", shouldContinue);
        shouldContinue = Console.ReadLine().ToUpper() == "Y";
    } while (shouldContinue == true);

    if (shouldContinue == false)
    {
        DisplayPhones(phones);
    }
}

Make all thos arrays properties of that class Phone and you will have just to access them where you want in that class. Beside of that you can use out insted of ref and not be aware of initialize everything befor run the code.

This your code rewritten to take advantage of a List<Phone> instead of arrays. As you can see the whole code is simplified a lot comparing to an array based approach

class Phone
{
    // Property to store the fields of a Phone object
    public string Manifacturer {get;set;}
    public string Model {get;set;}
    public string IsCordless {get;set;}
    public decimal Price {get;set;}

    // No parameters to pass, but returns a Phone instance 
    static Phone inputPhone()
    {
        Phone p = new Phone();
        Console.Write("Enter the phone manufacturer: ");
        p.Manufacturer = Console.ReadLine();
        Console.Write("Enter the phone model: ");
        p.Model = Console.ReadLine();
        Console.Write("Is it cordless? [Y or N]: ");
        p.IsCordless = Console.ReadLine().ToUpper() == "Y";
        Console.Write("Enter the phone price: ");
        p.Price = Convert.ToDecimal(Console.ReadLine());
        return p;
    }

    // Pass the list and loop on every element    
    static void outputPhones(List<Phone> pList)
    {
        foreach (Phone o in pList)
        {
            Console.WriteLine("Phone Manufacturer: {0}", p.Manufacturer);
            Console.WriteLine("Phone Model: {0}", p.Model);
            Console.WriteLine("Has Cord: {0}", p.IsCordless ? "Yes" : "No");
            Console.WriteLine("Phone Price: {0}", p.Price);
        }
        Console.WriteLine("Number of phones entered: {0}", pList.Count);
    }

    static void Main(string[] args)
    {
        // Initialize an empty Phone list
        List<Phone> pList = new List<Phone>();
        bool continueLoop = true;

        do
        {
            // Get the input from the user and add to the list
            Phone p = inputPhone();
            pList.Add(p);
            Console.Write("Would like to process another phone? [Y or N]: ", continueLoop);
            continueLoop = Console.ReadLine().ToUpper() == "Y";
        } while (continueLoop == true);

        // output the list    
        outputPhones(pList);

    }
}

Why not make phone a class:

public class Phone
{
    public double Price {get;set;}
    public string Manufacturer {get;get;}
    public string Model {get;set;}
    public bool HasCord{get;set;}

    public override string ToString()
    {
        return string.Format("Phone Manufacturer: {0}\nPhone Model {1}\nHas Cord: {2}\nPhone Price{3}", this.Manufacturer, this.Model, this.HasCord ? "Yes" : "No", this.Price);
    }
}

Then, you can change your program to be more object oriented and look like:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace newProg
{
    class YourApp
    {
        private Phone inputPhone()
        {
            Console.Write("Enter the phone manufacturer: ");
            string manufacturer = Console.ReadLine();

            Console.Write("Enter the phone model: ");
            string model = Console.ReadLine();

            Console.Write("Is it cordless? [Y or N]: ");
            bool hasCord = Console.ReadLine().ToUpper() == "Y";

            Console.Write("Enter the phone price: ");
            double price = Convert.ToDouble(Console.ReadLine());

            return new Phone {
                Manufacturer = manufacturer,
                Model = model,
                HasCord = hasCord,
                Price = price;
            };
        }

    static void outputPhones(List<Phone> phones)
    {
        foreach (var index = 0; index < phones.Length; index++)
        {
            Console.WriteLine("==Phone #{0}==", index);
            Console.WriteLine(phone.ToString());
        }
        Console.WriteLine("Number of phones entered: {0}", phones.Length);
    }

    static void Main(string[] args)
    {
        List<Phone> phones = new List<Phone>();

        bool Continue = true;

        do
        {
            phones.Add(inputPhone());
            Console.Write("Would like to process another phone? [Y or N]: ", Continue);
            Continue = Console.ReadLine().ToUpper() == "Y";
        } while (Continue == true);

        if (Continue == false)
        {
            outputPhones(phones);
        }
    }
}