OK, now you're moving on to a completely different issue.
So far, we have just been talking about sending bytes out of the UART, and receiving bytes from the UART; now you're moving on to consider what to do with those bytes once they've been received.

If you want the bytes to be stored to particular locations in the 8051's memory, you will need some sort of protocol to supply that information; you will need to send both the data and its intended address over the serial link.
Similarly if you want to read data from specific 8051 adresses.

You might want to consider the standard Intel Hex format to do this - as it was designed precisely for this very job!
See: http://www.8052.com/forum/read.phtml?id=65179

As we are moving on to a new subject, I suggest you start a new thread - with a link to this one - and state precisely what it is that you are trying to do.
But don't just type it straight in to the forum; take some time to think about what you need to do, write it out on paper - you may well find that you answer many of your own questions in doing so!