fact.asm

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TITLE Calculating a Factorial                   (Fact.asm)

; This program uses recursion to calculate the
; factorial of an integer.
; Last update: 11/23/01

INCLUDE Irvine32.inc

.code
main PROC
	push 12		; calc 12!
	call Factorial		; calculate factorial (eax)
ReturnMain:
	call WriteDec		; display it
	call Crlf
	exit
main ENDP

Factorial PROC
	push ebp
	mov  ebp,esp
	mov  eax,[ebp+8]		; get n
	cmp  eax,0		; n < 0?
	ja   L1		; yes: continue
	mov  eax,1		; no: return 1
	jmp  L2

L1: dec  eax
	push eax		; Factorial(n-1)
	call Factorial

; Instructions from this point on execute when each
; recursive call returns.

ReturnFact:
	mov  ebx,[ebp+8]   		; get n
	mul  ebx          		; ax = ax * bx

L2: pop  ebp		; return EAX
	ret  4		; clean up stack
Factorial ENDP

END main