/* Calculate the factorial of the number held in variable A.
 * The number in variable A must be greater than 0 and less than or equal 
 * to 6! = 720 (note: 5! = 120)
 * Store factorial of A into 16 bit variable C. Byte ordering is little endian.
 * C = A!
 */
.INCLUDE <m328pdef.inc> 

.DSEG
A:     .BYTE 1
C:     .BYTE 2

.CSEG
Fact1_6:
	lds  r16, A
	clr  r0
	inc  r0          ; r0 = 1
fact1_6a:
    mul  r0, r16 
    dec  r16
	brne fact1_6a
	sts  C, r0    ; least significant byte (little end)
	sts  C+1, r1  ; most  significant byte (big end)

rjmp Fact1_6