static void Enqueue (string toInsert)
{

	Node cur = head;

	if (cur == null)
	{
		head = new Node(toInsert);
	}
	else
	{
		while (cur.next != null)
		{
			// SLOW - NOT GOOD
			cur = cur.next;
		}

		cur.next = new Node(toInsert);
	}
}

- - - 

static void Enqueue (string toInsert)
{
	if (head == null)
	{
		head = new Node(toInsert);
		tail = head;
	}
	else
	{
		tail.next = new Node(toInsert);
		tail = tail.next;
	}
}

- - - 

static string Dequeue ()
{
	if (head == null)
		return "";

	string rv = head.data;
	head = head.next;
	return rv;
}

- - - 

static void Push (string toInsert)
{
	Node temp = new Node(toInsert, head);
	head = temp;
}

- - - 

static string Pop ()
{
	if (head == null)
		return "";

	string rv = head.data;
	head = head.next;
	return rv;
}

-----------------------------------------

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace _2313_keypress_example
{
    public partial class Form1 : Form
    {
        private int _x;
        private int _y;

        private const int MapWidth = 100;
        private const int MapHeight = 50;

        public int X
        {
            get { return _x; }
            set { if ((value >= 0) && (value < MapWidth))
                    _x = value;
            }
        }

        public int Y
        {
            get { return _y; }
            set
            {
                if ((value >= 0) && (value < MapHeight))
                    _y = value;
            }
        }

        public Form1()
        {
            InitializeComponent();

            X = 40;
            Y = 40;
        }

        private void Form1_KeyDown(object sender, KeyEventArgs e)
        {
//            MessageBox.Show(e.KeyCode.ToString());
            switch (e.KeyCode)
            {
                case Keys.Up: Y--; break;
                case Keys.Down: Y++; break;
                case Keys.Left: X--; break;
                case Keys.Right: X++; break;
            }

            label1.Text = "x=" + X + " y=" + Y;
        }

        private void Form1_KeyPress(object sender, KeyPressEventArgs e)
        {
//            MessageBox.Show(e.KeyChar.ToString());
        }
    }
}