section .data
    num db 5
    result db 0,0,0,0
section .text
    global _start
    _start:
        mov ax,1
        mov bh,0
        mov bl,[num]
    call fact
    mov rsi,result    ; convert to ascii and display
    mov cl,4          ;  iter1 ax=78       iter2
    up:
        rol ax,4      ;       ax=87         ax = 78
        mov dx,ax         ;       dx = 87       dx=78
        and ax,0fh        ;       ax=07         ax=08
        cmp al,09
        jbe skip          ;if given digit is greater than 9,cy=0 else cy=1(if cy=1 then jump)
        add al,07
        skip:
            add al,30h
            mov [rsi],al       ; result[0]=37       result[1]=38
            inc rsi            ;  result++
            mov ax,dx          ; ax = 87            ax = 78
            dec cl             ; cl= 3              cl = 2
            jnz up
            mov rax,1
            mov rdi,1
            mov rsi,result        ;      display string i.e. result= 78
            mov rdx,4
            syscall

mov rax,60
mov rdi,0
syscall

; procedure - recursive   iteration 1      2         3       4
fact:
    cmp bx,1
    jne next                             
ret
next:
    mul bx      ; ax*bx            ax =5     20       60       120
    dec bx            ;            bx = 4    3         2       1
    call fact
ret