Factorial

.MODEL EXTRA LARGE
.STACK 100H
.DATA
    N DB ?


.CODE
    MAIN PROC

    MOV AX,@DATA
    MOV DS,AX

    CALL FACT

    CALL PRINT

    MOV AH,4CH
    INT 21H

    MAIN ENDP

    FACT PROC
        MOV CX,3 ; INPUT
        MOV AX,1 ; OUTPUT

        REAP:
            MUL  CX  ; N = N * ( N - 1 )
            LOOP REAP

    ESCAPE:
        RET
    FACT ENDP

    ; DATA NEEDS TO PRINT IN DECIMAL FORMAT
    PRINT PROC
        OR  AX, AX ; AX < 0
        JGE END_IF1 ; NO > 0

        PUSH AX
        MOV DL,'-'
        MOV AH,2
        INT 21H
        POP AX

        END_IF1:
            XOR CX, CX ; FOR COUNTING HOW MANY DIGITS
            XOR DX, DX ; MAKE DATA SEGMENT CLEAR
            MOV BX, 10D
            SEC1:
                XOR     DX, DX
                DIV     BX
                PUSH    DX
                INC     CX

                OR      AX,AX
                JNE     SEC1

                MOV     AH,2

            PRINTLOOP:
                 POP    DX
                 OR     DL,30H
                 INT    21H
                 LOOP   PRINTLOOP

    ESC:
        RET
    PRINT ENDP


END MAIN