Doubt in Table Control

HI Gurus,

can some one tell me why we are using the module

module RACUNI_mark input.

and the field WA_OUTPUT-CHECK. in the code below. Thanks a lot.

PROCESS AFTER INPUT.

*&spwizard: pai flow logic for tablecontrol 'RACUNI'

loop at IT_OUTPUT.

chain.

field WA_OUTPUT-BROJPL.

field WA_OUTPUT-BROJST.

field WA_OUTPUT-BELNR.

field WA_OUTPUT-REFERENCA.

field WA_OUTPUT-IZNOS.

field WA_OUTPUT-SIROVINA.

field WA_OUTPUT-JM.

field WA_OUTPUT-CENA.

field WA_OUTPUT-UGKOL.

module RACUNI_modify on chain-request.

field WA_OUTPUT-CHECK

module RACUNI_mark on request.

endchain.

endloop.

module RACUNI_user_command.

this is module.

module RACUNI_modify input.

MODIFY IT_OUTPUT

from WA_OUTPUT

index RACUNI-current_line.

endmodule.

module RACUNI_mark input.

data: g_RACUNI_wa2 like line of IT_OUTPUT.

if RACUNI-line_sel_mode = 1

and WA_OUTPUT-CHECK = 'X'.

loop at IT_OUTPUT into g_RACUNI_wa2

where CHECK = 'X'.

g_RACUNI_wa2-CHECK = ''.

modify IT_OUTPUT

from g_RACUNI_wa2

transporting CHECK.

endloop.

endif.

modify IT_OUTPUT

from WA_OUTPUT

index RACUNI-current_line

transporting CHECK.

endmodule.

*&spwizard: input module for tc 'RACUNI'. do not change this line!

*&spwizard: process user command

module RACUNI_user_command input.

OK_CODE = sy-ucomm.

perform user_ok_tc using 'RACUNI'

'IT_OUTPUT'

'CHECK'

changing OK_CODE.

sy-ucomm = OK_CODE.

endmodule.