Do Until Cell IsEmpty

I am trying to break up a bigger question into smaller bit so that I understand the steps.

I have:

Cell
A1 = 1 B1 = 2
A2 = 3 B2 = 4
A3 = 5 B3 = 6

How do I write a code such that

E1 = A1 and F1 = B1
Then
E1 = A2 and F1 = B2
Then
E1 = A3 and F1 = B3
Then
It stops because A4 is empty.

I really feel like a baby because I know what I want but find it hard to convey the message, I really hope someone would help me. I had a bigger problem which I had posted earlier but made no progress so I'm breaking down to this bit size first.

Thanks.