I want to fix a code  in vhdl.i have to give the numbers from 0-255 as 
input and i want to take in outout the nymbers in hex system in 2 seven 
segment display.

And the question is what is the question?!

i dont know how to do this..how i will present the naumbers in the 2 
dispay??

here you can find display patterns for the digits 0 to f used in HEX 
representation
http://en.wikipedia.org/wiki/Seven-segment_display_character_representations

I'm afraid your question is incomplete. So I'm now guessing:

- I believe you have an eight bits wide unsigned input vector.
- I also estimate that your seven segment displays are connected to your 
FPGA 1:1 and thus do not need to be multiplexed.

If I'm right with both estimations, the simplest way for you to do it is 
the following:

- In your thoughts, split up your eight bits wide vector into two four 
bits wide vectors, each of them serving one display.
- For each four-bit-vector, instantiate a truth table converting all 
input value patterns possible (0..15) into their correct representations 
on your display.

I suppose you're a VHDL beginner. Here's a good tutorial: 
http://www.seas.upenn.edu/~ese171/vhdl/vhdl_primer.html

The truth tables could be implemented with a SELECT or a CASE statement, 
for example.

Patrick