new to macs

Hi I have recently been asked a few questions about an imac system. I am more than competent on any pc however macs are still very new territory to me. Firstly the cmac in question has a partition on the harddrive, what equivelant program to fdisk is available for it in order to remove/alter the partition. How do I format a partition on a mac. the system in question is running os 9 (I think :D) Any help or information would be greatly appreciated. Thanks