8051 simple program

Hello,
i am beginer with asembler and i need help with my program. I am trying to write program to print arithmetic average of numbers in external memory, last number is 0FFH, numbers are positive and negative 8 bit. Could you help me or send some link for this problem? I have read many tutorials but i could not solve this problem.
Thank you very much
Marek

Many of our members program the 8051 in assembly, so I hope they will help.
You have to tell us what you have done,what works and what does not.

Your latest code and a diagram of your hardware would help.