How to declare internal table with header line and without header line.

internal table with header line.

data: begin of itab occurs 0,
       num1 type i,
       num2 type i,
       ........,
       ........,
      end of itab.

internal table without header line.

types: begin of itab,
        num1 type i,
        num2 type i,
        ........,
        ........,
       end of itab.
data: itab1 type itab occurs 0.


Internal table is declared by many ways:

(A)
Data : BEGIN OF IT_TAB occurs 10,
       num1 type i,
        num2 type i,
       END OF IT_TAB.

(B)
TYPES : BEGIN OF tT_TAB,
        num1 type i,
        num2 type i,
        END OF tT_TAB.

DATA : tT_TAB TYPE STANDARD TBLE OF tT_TAB with header line.

(C)
TYPES : BEGIN OF tT_TAB,
        num1 type i,
        num2 type i,
        END OF tT_TAB.

DATA : iT_TAB TYPE STANDARD OF tT_TAB.
   
(D)
DATA : BEGIN OF IT_TAB,
       num1 type i,
        num2 type i,
       END oF IT_TAB.

DATA : wa_TAB LIKE LINE OF IT_TAB,
       wa_TAB TYPE OF IT_TAB