DNS SOA Question in regards to @

Okay, I have a question guys... I was given a task to set up a DNS slave server, in addition to our already set up BIND DNS master server. I looked over the one of the zone files, and found something curious. The starting SOA line, reads as:

@ IN SOA @ root ( ...etc...etc..)

I'm a bit confused as to the meaning of the @ symbols. The first @ symbol can replace the $origin term I know, but there is no $origin variable declared in the file The only thing that comes before the SOA is the TTL.

So I"m baffled as to what the @ could possibly do or if it can substituted for anything else, without explicitly saying it. Because I see no declarations in the zone file.

Any help would be appreciated! Thanks!

You dont need to explicitly declare ORIGIN. In your case the @ symbol is just saying "this zone".

For the unix.com zone file for example, you'd read it as unix.com. IN SOA ...