Write a subroutine in C for toggling the cursor using old directives.

;

; use small memory model for C - near code segment

_DATA SEGMENT WORD   'DATA'

  CURVAL EQU   [BP+4]   ; parameters

_DATA   ENDS

_TEXT                     SEGMENT        BYTE              PUBLIC         'CODE'

DGROUP                GROUP _DATA

                                 ASSUME CS:_TEXT,  DS:DGROUP,  SS:DGROUP

                                 PUBLIC _CURSW

_CURSW PROC    NEAR

                                 PUSH    BP    ; BP register of caller is saved

                                 MOV    BP, SP    ; BP is pointing to stack now

                                 MOV   AX, CURVAL

                                 CMP   AX, 0H

                                 JZ    CUROFF; Execute code for cursor off

                                 CMP   AX, 01H  

                                 JZ    CURON; Execute code for cursor on

                                 JMP    OVER    ; Error in parameter, do nothing 

CUROFF:      ; write code for curoff

:

 :

                                  JMP   OVER

CURON:      ; write code for curon

:

 :

OVER:                        POP BP

                                    RET

_CURSW                    ENDP

_TEXT                        ENDS

  END

Why the parameter is found in [BP+4]? Please look into the following stack for answer.