your question seems to indicate that you are using assembler.
1) are you?
2) which assembler are you using? the answer is NOT the same for all
Then you post:
To call a subroutine from other file simply add "$ include < filename>" in the coding anywhere and use it after wards.
Again that may be right and may be wrong depending on which assembler he uses why do you answer before he answers the questions posted to him.

Erik