Program to Perform Addition in Function (Assembly language)

This Program perform addition using Functions in assembly language. Addition in assembly language programming

.MODEL SMALL
.STACK 100H
.DATA
        S1 DB "sum is : $ "
        
.CODE
        MAIN PROC 
        MOV AX,@DATA
        MOV DS,AX
        mov ax,'3'
mov bx,'2'
push ax
push bx
        CALL SUM
        MOV DX,OFFSET S1
        MOV AH,9
        INT 21H
MOV DX,CX
        SUB DX,30H
MOV AH,2 
INT 21H        
mov bp,sp 
        mov word ptr [bp] ,'8'
MOV AH  ,2
        MOV DX , word ptr [bp]
INT 21H
MOV AH,4CH
        INT 21H
        MAIN ENDP
        SUM PROC
PUSH BP
MOV BP,SP
PUSH BX
PUSH AX
MOV BX,[BP+4]
        MOV AX,[BP+6]
ADD AX,BX
MOV CX,AX
POP AX
POP BX
POP BP
        RET 4
SUM ENDP
        END MAIN