8051 microcontroller programming:Tutorial-factorial in assembly with Keil

Finding factorial is one of the basic programs.
It's a good practice code.
Factorial is given as:
n!=n*(n-1)*(n-2)*..........................*1
PROGRAM:

 ORG 00H
  MOV DPTR,#2000H
  MOVX A,@DPTR
  MOV R0,A
  MOV A,#01H
  MOV B,A
  MOV R1,A
LOOP: MUL AB
  MOV R5,B
  MOV B,A
  MOV A,R1
  INC A
  MOV R1,A
  DJNZ R0,LOOP
  MOV A,R5
  INC DPTR
  MOVX @DPTR,A
  MOV A,B
  INC DPTR
  MOVX @DPTR,A
  END