Hello,
Try to debug a code and keep your eye on SY_TABIX and SY_INDEX field in top right of the debugger.
You will see that :
SY_TABIX - represent the current executing line of the table. Work only for INDEX tables. For Hash tables it is set to 0 or blank .
Some of the statement that fill SY_TABIX are SELECT, APPEND ,LOOP AT .. , READ TABLE etc.
SY_INDEX - keep the counter of the current executing iteration (loop).
Best Regards,
Praveen