C#

for (int i = n; i > 0; i--)<br />
    //(And when you use it write)<br />
     i-1;

This can all be done programatically, but it takes some work. Look at the Microsoft.Win32 namespace for registry manipulation functions.
1) Create a key by the name of the file extension you want
2) Set the default attribute of this key to a word that describes your program. It's name doesn't really matter.
3) Create a key by the name of the word you decided on in step 2.
4) Create some subkeys: 'DefaultIcon' and 'shell'
5) Set the default attribute of the DefaultIcon key to the path of your icon. If you want to use the the same icon
   as your executable, do something like this: <code>c:\code\mysupercoolapp\exefile.exe,0</code>
6) Create a 'open' subkey under 'shell' and a 'command' subkey under open
7) Set the default attribute of the 'command' key to the path of your program (include the %1) <code>c:\code\mysupercoolapp\exefile.exe %1</code>
8) Restart
9) When a file with the extension you've picked is double-clicked, your application will run.
   The first argument will be the path of the file.