OK, let me confess. I too was quite confused about IP classes and how exactly the classification is done. But after watching this video, it feels like the thing was piece of cake.
Check it out:
Now that you know how will you investigate a given IP address, why not try to analyze your OWN IP address that is currently assigned to you by PTCL or Linkdotnet , or whatever ISP you are using?
Find your own IP address at http://whatismyip.com
If you are using PTCL DSL, it will start from either 119 or 116. Do the rest on your own