Strange way of writing robots.txt

Has anybody use this?

[Cyclob]

hi...

I'm curious of what is the different between

User-agent: *
Disallow:

and

User-agent: *
Disallow: /

Is the first one give the meaning as "allow"? or is it valid?

Somebody please explain to me please. Thank you very much in advance.

Cyclob

[WiseWebDude]

Cyclob,

User-agent: *
Disallow:

Disallows NOTHING, all is allowed.

User-agent: *
Disallow: /

Disallows ALL, nothing is allowed.