Progamming Ruby中扩展irb问题

Programming php?name=Ruby" onclick="tagshow(event)" class="t_tag">Ruby的15.2.2扩展irb中，将到将一段代码添加到 .irbrc文件中就可以扩展一个叫做ri的方法。但是我始终没有找到.irbrc文件。
我用的Windows下的系统。
还请知道的指点一下，十分感谢！！！！！！！！！！

Create a file called anything you like (e.g. “_irbrc” or “irb.rc”) and place it anywhere you like (say C:\Documents and Settings\), and set that full path to the ENV variable IRBRC, e.g. C:\Documents and Settings\\_irbrc

on win32 I have just set an IRBRC=\path\to\file env variable and it works fine

谢了谢了谢了