Stack with capacity, bottom items beyond the capacity are discarded.

RoundStack.cs

/// <summary>
/// Stack with capacity, bottom items beyond the capacity are discarded.
/// </summary>
/// <typeparam name="T"></typeparam>
[Serializable]
public class RoundStack<T>
{
    private T[] items; // items.Length is Capacity + 1

    // top == bottom ==> full
    private int top = 1;
    private int bottom = 0;

    /// <summary>
    /// Gets if the <see cref="RoundStack&lt;T&gt;"/> is full.
    /// </summary>
    public bool IsFull
    {
        get
        {
            return top == bottom;
        }
    }

    /// <summary>
    /// Gets the number of elements contained in the <see cref="RoundStack&lt;T&gt;"/>.
    /// </summary>
    public int Count
    {
        get
        {
            int count = top - bottom - 1;
            if (count < 0)
                count += items.Length;
            return count;
        }
    }

    /// <summary>
    /// Gets the capacity of the <see cref="RoundStack&lt;T&gt;"/>.
    /// </summary>
    public int Capacity
    {
        get
        {
            return items.Length - 1;
        }
    }

    /// <summary>
    /// Creates <see cref="RoundStack&lt;T&gt;"/> with given capacity
    /// </summary>
    /// <param name="capacity"></param>
    public RoundStack(int capacity)
    {
        if (capacity < 1)
            throw new ArgumentOutOfRangeException("Capacity need to be at least 1");
        items = new T[capacity + 1];
    }

    /// <summary>
    /// Removes and returns the object at the top of the <see cref="RoundStack&lt;T&gt;"/>.
    /// </summary>
    /// <returns></returns>
    public T Pop()
    {
        if (Count > 0)
        {
            T removed = items[top];
            items[top--] = default(T);
            if (top < 0)
                top += items.Length;
            return removed;
        }
        else
            throw new InvalidOperationException("Cannot pop from emtpy stack");
    }

    /// <summary>
    /// Inserts an object at the top of the <see cref="RoundStack&lt;T&gt;"/>.
    /// </summary>
    /// <param name="item"></param>
    public void Push(T item)
    {
        if (IsFull)
        {
            bottom++;
            if (bottom >= items.Length)
                bottom -= items.Length;
        }
        if (++top >= items.Length)
            top -= items.Length;
        items[top] = item;
    }

    /// <summary>
    /// Returns the object at the top of the <see cref="RoundStack&lt;T&gt;"/> without removing it.
    /// </summary>
    public T Peek()
    {
        return items[top];
    }

    /// <summary>
    /// Removes all the objects from the <see cref="RoundStack&lt;T&gt;"/>.
    /// </summary>
    public void Clear()
    {
        if (Count > 0)
        {
            for (int i = 0; i < items.Length; i++)
            {
                items[i] = default(T);
            }
            top = 1;
            bottom = 0;
        }
    }

}