Hi
On layer 2 switches you can still have a L3 interface but it is only used for management. So typically unless you change it, it will be vlan 1 eg.
vlan 1
ip address 192.168.5.4 255.255.255.0
ip default-gateway 192.168.5.1
where 192.168.5.1 is a routed interface on either a router or layer 3 switch.
You should not use the vlan 1 interface as a default-gateway for any of your client PC as it is purely to allow you to access the switch.
HTH
Jon