You probably played back in JH or HS during your computer classes that always seemed to be on the computers there.
Was it Battle Tanks? Something like that I can't remember. I think its freeware now but I can't remember for the love of god what it was and I am trying to download it again haven't played it in years.
Basically there were two tanks on either side of the screen taking turns trying to hit each other using terrain, elevation and slight movement. You also had special rounds including the nuke

. Anyone remember this and what it was called?