mysterious ushort arrays with hex

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C#

Hi folks,

right, so the following is a code snippet from someone else who is just using it without bothering how it does what it does. This code is a part of the class that can be used to generate Excel files using C# and NOT using interop. I must say it works, but, i m a bit brain-numbed by the ushort[] arrays and the hex-magic going on. Please have a look and see if you could help me demystify them:

public sealed class ExcelWriter : IDisposable
      {
            // private Stream stream;
            private readonly BinaryWriter writer;

            private readonly ushort[] begin = { 0x0809, 8, 0, 0x10, 0, 0 };
            private readonly ushort[] end = { 0x0A, 00 };

            public ExcelWriter(Stream stream)
            {
                  // this.stream = stream;
                  writer = new BinaryWriter(stream);
            }

            public void WriteCell(int row, int col, string value)
            {
                  ushort[] data = { 0x0204, 0, 0, 0, 0, 0 };
                  var len = value.Length;
                  var plainText = Encoding.ASCII.GetBytes(value);
                  data[1] = (ushort)(8 + len);
                  data[2] = (ushort)row;
                  data[3] = (ushort)col;
                  data[5] = (ushort)len;
                  WriteUshortArray(data);
                  writer.Write(plainText);
            }
...
}

I am interested in dissecting the WriteCell() method in particular, which is actually called by a main method, if u will, to write out values from a DataTable using BinaryWriter and FileStream (pretty much standard stuff). I tried something like this which is a heavily stripped down and de-fattened version of this code:

BinaryWriter bw = new BinaryWriter(new FileStream(@"Z:\temp.xls", FileMode.OpenOrCreate));
            bw.Write(ASCIIEncoding.ASCII.GetBytes("HELLO\r\n"));
            bw.Write(ASCIIEncoding.ASCII.GetBytes("HELLO\r\n"));
            bw.Write(ASCIIEncoding.ASCII.GetBytes("HELLO\r\n"));
            bw.Flush();
            bw.Close();

When I open temp.xls, it opens with a warning about a different format but I can still see my data there. SO I imagine that those little "hexadecimal druids" are doing something mystical that opens the file without any warning.

Please don't point me to "Hexadecimal for Dummies" kinda websites, i know what they are I just want to know what the hell they are doing in an Excel generation code and how? :)

Many thanks...