analog programming

I want to know how in plc some rtd (temperature sensor ) value can get
converter after the analog to digital converter in anlog module to actual value of temperature .
means that how can I get 4 to 20 ma to some digital byte or word , & how many of bits it contain in plc for after conversion & this bits are converted in to actual integer value of temperature .
so please give some example for all this process.

The procedure to convert from a raw measured value into the standard representation of a value is know as "scaling". Please refer to this thread for a discussion.