SimpleStack.cs

using System;

namespace CsharpCodeExamples
{
    class Program
    {
        public class SimpleStack<T>
        {
            int top;
            private T[] data;

            public SimpleStack(int bufferLength)
            {
                data = new T[bufferLength];
            }

            public void Push(T value)
            {
                if (top == data.Length - 1) throw new StackOverflowException();

                // Stacks are constant time becouse we always directly accessing "top nr" item in the data array.  
                // We dont have to look at any other item in the array we know exactly which number item we want
                data[top++] = value;   
            }

            public T Pop()
            {
                if (top == 0)
                    return default(T);

                // Stacks are constant time becouse we always directly accessing "top nr" item in the data array.  
                // We dont have to look at any other item in the array we know exactly which number item we want
                return data[--top];
            }
        }

        static void Main(string[] args)
        {
            // Stacks are known as First in last out data structures.
            
            // Consider a stack of plates on a shelf.  
            // After you wash and dry your dishes you place (pop) each plate onto the stack.
            // When it is time to eat again you take the plate on the top of the stack (pop) to use first.

            // Pushing and poping plates on and off the stack are constant time operations.  It doesnt matter 
            // how many plates are on the stack it will always take the same amount of time to push or 
            // pop a new plate on or off of the stack

            //Initialze the stack with a max of 5 items on it.
            var mystack = new SimpleStack<int?>(5);
            mystack.Push(1);
            mystack.Push(2);
            mystack.Push(3);
            Console.WriteLine("Poped: " + mystack.Pop());   // should be three
            Console.WriteLine("Poped: " + mystack.Pop());   // Should be two
            Console.WriteLine("Poped: " + mystack.Pop());   // should be one
            Console.WriteLine("Poped: " + mystack.Pop());   // Null as there are no more items on the stack
            Console.ReadLine();
        }
    }
}
}