Please explain, the job of the "ASSIGN COMPONENT ".

Question

Please read this popular example appended below. I am newbie to ABAP.
At the end of the execution the code is printing 33. Don't get it.
Please explain,  the job of the  "ASSIGN COMPONENT ". How or why it is printing value 33.  What is the meaning of the statement, "ASSIGN COMPONENT <F2> OF STRUCTURE <F1> TO <F3>." ?
DATA: BEGIN OF LINE,
COL1 TYPE I VALUE '11',
COL2 TYPE I VALUE '22',
COL3 TYPE I VALUE '33',
END OF LINE.
DATA COMP(5) VALUE 'COL3'.
FIELD-SYMBOLS: <F1>, <F2>, <F3>.
ASSIGN LINE TO <F1>.
ASSIGN COMP TO <F2>.
DO 3 TIMES.
ASSIGN COMPONENT SY-INDEX OF STRUCTURE <F1> TO <F3>.
WRITE <F3>.
ENDDO.
ASSIGN COMPONENT <F2> OF STRUCTURE <F1> TO <F3>.
WRITE / <F3>.
11 22 33
33

Answer 1

DATA: BEGIN OF LINE,
COL1 TYPE I VALUE '11',
COL2 TYPE I VALUE '22',
COL3 TYPE I VALUE '33',
END OF LINE.
DATA COMP(5) VALUE 'COL3'.
FIELD-SYMBOLS: <F1>, <F2>, <F3>.
ASSIGN LINE TO <F1>.
ASSIGN COMP TO <F2>.      "here you are assigning the column name which is COL3 to <f2>.
DO 3 TIMES.
ASSIGN COMPONENT SY-INDEX OF STRUCTURE <F1> TO <F3>.
WRITE <F3>.
ENDDO.
ASSIGN COMPONENT <F2> OF STRUCTURE <F1> TO <F3>.
ASSIGN 'COL3' of structure <f1> to <f3>. "it is equal to above statement.
WRITE / <F3>.
11 22 33
33
ASSIGN COMPONENT <F2> OF STRUCTURE <F1> TO <F3>. means
assigining  COL3  value of the structure <f1> to <f3>, so value is 33 , it will be assigned to <f3> .it prints 33.