By default Class C subnet mask is 255.255.255.0 = 24 bits for network id and 8 bits for host id.
in Binary
1111 1111. 1111 1111. 1111 1111. 0000 0000
Here all 1s are Network bits and all 0s are host bits. For this subnet mask you can have 256 hosts. And you can use 254 host and asign IP address to them.
By Saurabh