any free txt file comparing tool recommend?

as title...i have two txt file need to be compare..any tools recommend? thanks
http://www.downloadjunction.com/product/freeware/4234/index.html

try, 我未試過的, 在 google 找出來
downloading let me try.. thanks
  it work..as i have many config files for network device need to be compare. thanks
linux/unix: diff a.txt b.txt