Partitioning external drive for use as Time Machine

Hello. This is my first post, having just moved over from Windows! I now have a 13" Macbook Pro.
I've just purchased a 1Tb external Buffalo drive. I was wondering if I could partition the drive to use 800Gb as a Time Machine, and 200Gb for saving random files to access as required.
Is this possible, and if so how do I do it? Or do I need a separate drive?
Many thanks.

Do it the same as you would any disk. Open up Disk Utility while the external drive is attached - select the external drive in the side bar and head for the Partition tab.

While not recommended as best practice, you can store data other than the TM backup within the same partition (I do - against my own recommendation - and I have the first gen Time Capsule which was supposed to have died several years ago according to a lot of reports about that version of it). So, you don't have to partition it, unless you like following best practice.

Thanks very much for the advice. Have partitioned the external drive and it all works fine.