Scrolling in Table Control ABAP Interview Questions

I have defined a table control and scrolling is not possible in that even if
the number of entries exceeds the window height. Below is the flow logic
which I have attached

PROCESS BEFORE OUTPUT.
MODULE STATUS_0300.
LOOP AT IT1 CURSOR ZTR0300-CURRENT_LINE.
ENDLOOP.
*
PROCESS AFTER INPUT.
LOOP AT IT1.
MODULE USER_COMMAND_0300.
ENDLOOP.

What could I have done wrong ?

Try defining the table control lines in PBO.

PROCESS BEFORE OUTPUT.
ZTR0300-CURRENT_LINE = 100.

Iam sorry, i have mentioned ZTR0300-LINES as ZTR0300-CURRENT_LINE in previous
one,.,,

PROCESS BEFORE OUTPUT.
ZTR0300-LINES = 100

That worked.