.TITLE    Factorial
;  Function Factorial (K)    Calculates K!  for 0 <= K <= 12

;  Argument List:
;  Parameter  Offset  Purpose             Type       Passed by
   K       =   4    ; Function argument   Longword   Reference

;  Result:
;  K!  returned as a longword in R0

;  Algorithm:
;    1.  Initialize Factorial = 1, Counter = K
;    2.  While Counter > 0 do
;           Multiply Factorial by Counter
;           Decrement Counter

         .DISABLE  GLOBAL

         .ENTRY    Factorial,  ^M<R2>

Begin:   MOVL      #1, R0          ; Initialize K Factorial
         MOVL      @K(AP), R2      ; Get K for Counter

Loop:    BLEQ      Done            ; Branch if Counter <= 0
         MULL2     R2, R0          ; Multiply R0 by Counter
         DECL      R2              ; Decrement Counter
         BRB       Loop            ; Repeat at loop

Done:    RET                       ; Return from function

         .END