C#

using System;
using System.Diagnostics;

public class Diff
{
  static void Main(string[] args)
  {
    if (args.Length != 2)
    {
      Console.Error.WriteLine("You must provide two filenames.");
      Environment.Exit(1);
    }

    string cmd = "cmd.exe";
    if (Environment.OSVersion.Platform == PlatformID.Win32Windows)
      cmd = "command.exe";

    Process p = new Process();
    p.StartInfo.UseShellExecute = false;
    p.StartInfo.RedirectStandardOutput = true;
    p.StartInfo.FileName = cmd;
    p.StartInfo.Arguments = string.Format(
      @"/c fc ""{0}"" ""{1}""", args[0], args[1]);
    p.Start();
    p.WaitForExit();

    string line = p.StandardOutput.ReadLine();
    while (line != null)
    {
      Console.WriteLine(line);
      line = p.StandardOutput.ReadLine();
    }
  }
}

[DllImport("gdi32.dll")]
 static extern int GetDIBits(IntPtr hdc, IntPtr hbmp, uint uStartScan,
   uint cScanLines, [Out] byte [] lpvBits, ref BITMAPINFO lpbmi, uint uUsage);