Iterative Quick Sort

using System;
using System.Runtime.InteropServices;

namespace IterativeQuickSort
{
    class Stopwatch
    {
        [DllImport("kernel32.dll")]
        extern static short QueryPerformanceCounter(ref long x);

        [DllImport("kernel32.dll")]
        extern static short QueryPerformanceFrequency(ref long x);

        private static double strt;
        public static double time;

        public static void Start()
        {
            long cnt = 0;
            long frq = 0;
            QueryPerformanceCounter(ref cnt);
            QueryPerformanceFrequency(ref frq);
            strt = (double)cnt / (double)frq;
        }

        public static void Stop()
        {
            long cnt = 0;
            long frq = 0;
            QueryPerformanceCounter(ref cnt);
            QueryPerformanceFrequency(ref frq);
            double c = (double)cnt / (double)frq;
            time = (c - strt) * 1000;
        }
    }
}