general doubt regarding class

Hi all,

can anyone tell under what class this method comes and how to find this.

iam getting this error

"P_FILE" is not type-compatible with formal parameter "FILE_NAME".

I have declared my p_file as

parameters : p_file like rlgrap-filename.

CALL METHOD cl_gui_frontend_services=>file_get_size

EXPORTING

file_name = p_file

IMPORTING

file_size = size.