gateway

hi all

hi somebody answer my question,

from one pc to one pc if we set both pc is same subnet without gateway , both able to ping each other.

but

my qyestion is when a network device like router, if it ip address is 192.168.18.1/24
and i put my pc be 192.168.18.25 without default gateway. Y the switch cant ping to the PC?

hope you can answer my question

thanks.

with regard
jack