Finding Factorial of 8, clr screen and printing result with Assembly

Note: ; using 16bit assembly programming and NASM assembler.

[ORG 100H] ; instialization of .com file

JMP MAIN ; jump to lable Main

string: db "= Result of Factorial 8 ( by r_t )$" ; string to print

 Facto: ; subroutine to fine factorial of 8

 MOV CX,7 ;
 MOV AX,8
 L1: 
 MUL CX ; multiplying ax and cx
 SUB CX, 1 ; decrimenting cx by 1
 
 JNZ L1 ; geting loop until cx goes to 0
 
 RET
 
 PrintNumber: ; subroutine to print integer number on screen
 push bp 
 mov bp, sp
 push es
 push ax
 push bx ; pussing some registers on stack
 push cx
 push dx
 push di
 
 MOV AX, 0XB800 ; video base address in ax
 MOV ES, AX ; pointing es to video base
 MOV AX, [bp+4] ; loading number in ax
 MOV BX, 10 ; using base 10 for division to get decimal digits
 MOV CX, 0 ; intializing count of digits
 
 NextDigit:
 
 MOV DX, 0 ; 0 upper half of dividend
 DIV BX ; dividing by 10
 ADD DL, 0x30 ; adding 30 in remainder to get ASCII values
 PUSH DX ; saving last got ASCII value on stack
 INC CX ; incrementing count of values
 CMP AX, 0 ; checking, is the qoutient reached to zero ?
 JNZ NextDigit ; if not, then do it again
 
 mov di, 0 ; pointing di to top left column
 
 NextPosition: ; its time to print on screen in correct order
 
 POP DX ; poping last stored ASCII value from the stack
 MOV DH, 0x07 ; adding normal attribut
 mov [es:di], dx ; printing character on screen
 add di, 2 ; moving to next screen location( 1 byte of attirbute + 1 byte of actual character)
 loop NextPosition ; do this for all the ASCII values stored on stack
 
 pop di
 pop dx
 pop cx
 pop bx ; restoring all registers
 pop ax
 pop es
 pop bp
 
 ret 2 ; returning from routine by clearing stack
 
 
 Clrscr: ; subroutine to clear the whole screen
 push es
 push ax
 push di
 
 mov ax, 0xb800 
 mov es, ax ; pointing es to video base
 mov di, 0 ; di is pointing top left column of screen
 
 nextloc:
 
 mov word [es:di], 0x0720 ; clearing next character on screen
 add di, 2 ; moving to next location of screen
 cmp di, 4000 ; checking, is whole screen cleared?
 jne nextloc ; if not then repeat
 
 pop di
 pop ax
 pop es
 
 ret
 
 GETCH: ; subroutine to get character from keyboar(acutally 
 MOV AH, 0
 INT 0X16 ; i am using it to stop the screen on last results)
 RET ; using keyboard services
 
 
MAIN: ; our main body of the program starts from here
 
 
 CALL Facto ; calling subrouting of factorial
 PUSH AX ; saving last counted factorial's result on stack 
 CALL Clrscr ; clearing whole screen
 
 CALL PrintNumber ; calling routine to print that result on screen

; setting cursor position using video services
 
 mov ah, 02h 
 mov bh, 0
 mov dh, 0h
 mov dl, 7h

 int 0x10

;printing string using dos services

 mov ah, 9
 mov dx, string
 int 0x21
 
 CALL GETCH ; calling getch() funtion 

 MOV AX, 0X4C00 ; terminating the program with no error
 INT 0X21

Output: