include 'emu8086.inc' 

lf  equ     0ah
cr  equ     0dh               

data segment  
N    dw     0    

data ends

stack segment
    dw   200h  dup(0)
stack ends

code segment
start:                  
; set segment registers:
    mov ax, data
    mov ds, ax

    CALL   CLEAR_SCREEN
    
    PRINT  cr
    PRINT  lf    
    PRINT  'Enter a Number : '
    CALL   SCAN_NUM       ;cx = entered number

    CALL   Fact1  ; parameter is in cx result is in ax
    PRINT  cr
    PRINT  lf    
    PRINT  'Nonrecursive Factorial : '
    CALL   PRINT_NUM_UNS

    CALL   Fact2  ; parameter is in cx result is in ax
    PRINT  cr
    PRINT  lf    
    PRINT  'Recursive Factorial : '
    CALL   PRINT_NUM_UNS

    ; wait for any key....    
    mov ah, 1
    int 21h
    
    mov ax, 4c00h ; exit to operating system.
    int 21h    
code ends

DEFINE_CLEAR_SCREEN
DEFINE_SCAN_NUM
DEFINE_PRINT_STRING
DEFINE_PRINT_NUM
DEFINE_PRINT_NUM_UNS  ; required for print_num.
DEFINE_PTHIS


Fact1   PROC
    ; cl is parameter1 and equal to N
    mov     ch , 0
    mov     si , 2 
    mov     ax , 1 
For1:    
    cmp     si , cx
    ja      endFor1   ; jump if (si>cx)
    
    mul     si  ; dx:ax = ax * si
    
    inc     si  ; si++   
    jmp For1 
endFor1:
    ret
Fact1   ENDP    

Fact2   PROC
    ; cl is parameter1 and equal to N
    mov     ch , 0
if: 
    cmp     cl , 1
    ja      else

        mov     ax , 1
        ret
else:
    push    cx
    
    dec     cx
    call    Fact2  ; parameter is in cx result is in ax
    pop     cx                                         
    
    mul     cx
    ret
Fact2   ENDP    

   
PushALL MACRO
    push    ax
    push    bx
    push    cx
    push    dx
    push    si
    push    di
    push    bp
    push    sp
PushALL ENDM   
PopALL MACRO
    pop    sp
    pop    bp
    pop    di
    pop    si
    pop    dx
    pop    cx
    pop    bx
    pop    ax
PopALL ENDM   
end start ; set entry point and stop the assembler.