Please explain the meaning of "with control f" addition in loop at statemen

loop at g_MATERIALS_itab

into g_MATERIALS_wa

with control MATERIALS

cursor MATERIALS-current_line.

module MATERIALS_move.

module MATERIALS_get_lines.

endloop.

please lemme know wht effect does "with control MATERIALS" addition statement have in this loop.

Here MATERIALS is a Screen table.