Hey guys

My first post of many

I searched high and low but couldn't find an answer so I'm hoping this is the right place and you can help me.

I want to know how an exchange handles the coins someone deposits and if when you decide to withdraw your coins, are they the EXACT same coins as you deposited or, are they different coins, as the exchange pooled them with other coins and simply gives the coins the coins out without respect to the account that deposited them?

Please move this to the correct section if I didn't post in the right place.

Thanks in advance everyone