OFDM Questions

Hi all , i have some questions :

In OFDM Modulator Block , in Mapper Sub-block , in path of :

1- I saw the following comment inside the code : " Eventually, we will
get rid of the occupied_carriers concept. " , the question how you get
of the occupied carriers concept in the code and why ? . as i see the
depends strongly on this concept .

2- Why the concept of occupied carriers is used and why filling only
of FFT size not all of it ?

3-Inside the code , string carriers = “FE7F” . I have two questions
, the first is , when converting to bits : 1111111001111111 , why there
two zeros at DC instead of one zero only ?
The second question is , you started with “FE7F” . Why didn’t you
with “E7” and then pad F’s from both sides (looping) as you did later

4- Also , for the following segment of the code : diff =
(d_occupied_carriers - 4*carriers.length()) . Why you are multiplying
four instead of eight when converting from Character Domain to Bit
Domain ?
or you deal with them as HEX only ?

5- What is the maximum packet size ?

6- What is the difference between the word “coming message” and "
packet" .
Are they the same thing ? or Does one message contain more than one

Thanks in-advance