STACK SEGMENT STACK
DB 328 DUP(?)
STACK ENDS
DATA SEGMENT
C DB ?
DATA ENDS
CODE SEGMENT
ASSUME CS:CODE,DS:DATA,SS:STACK

;ax = S(dx,bx)
S PROC
cmp bx, dx
jne CMP0
mov AX, 1
ret
CMP0: cmp bx,0
jne CALC
mov ax, 0
ret
CALC: dec dx
dec bx
call S
mov cx,ax
push bx
inc bx
call S
push cx
mul bx
pop cx
pop bx
add ax, cx
ret
S ENDP
START: MOV AX,DATA
MOV DS,AX
MOV dx, 5
mov bx, 2
xor ax,ax
CALL S
mov bx,ax
mov ax, 01h
int 21h

MOV AX,4C00H
INT 21H

CODE ENDS
END START