cisco switch DHCP

At my job, we have 3 floors each floor PCs get a IP address on different subnet. For example: floor 50, get 10.1.50.x and 51 gets 10.1.51.x and so on. The default gateway on the PCs is the switch ip address. The question is how is this posible?. Is this done at the switch layer?
I was ready about cisco switches and there is something call like DHCP agent. We are using cisco 3560 series.
Thank you