"if one wants to convert the o/p to ASCII STRING its ok, how could you convert a 8 bit number to ASCII code as it itself code for some character"

Yes, you can't convert an 8 bit number to a single ASCII code unless it happens to be between zero and nine. Any greater and you'll have a string of, er, ASCII characters. I can't understand why you might think the poster doesn't appreciate this.

What really confused me though was all the stuff about 'A' and 40.