C#

static string UlongToString(ulong value)
{
    int ulongsize = sizeof(ulong) * 8;
    StringBuilder ret = new StringBuilder(ulongsize);

    for (int i = 0; i < ulongsize; i++)
    {
        ret.Insert(0, value & 0x1);
        value >>= 1;
    }

    return ret.ToString();
}

do
{
   ret.Insert(0, value & 0x1);
   value >>= 1;
}
while (value != 0);

Int32 x = 15;
String s = x.ToString("");

string binaryString = Convert.ToString(unchecked((long)ulong.MaxValue), 2);

//Changelog:
//4/25/2008
// -Original post by SpacixOne
//4/30/2008 
// -Updated Exception handler from Greeeg's suggestion.
// -Changed to more appropriate namespace
using System;
using System.Collections.Generic;
using System.Text;
using System.Net;
using System.IO;

namespace NeedsCode
{
    class Program
    {
        static void Main(string[] args)
        {
            throw new NotImplementedException("CodeProject is not a free homework service.");
        }
    }
}

flowingsun wrote:

how many times a word is used in a sentence,or its frequency

flowingsun wrote:

“this is a dog and that is a pig”
result:
“is”:2
“and”:1
th:2
is:3
i:4