汇编语言-求X的阶乘

1. 题目：求X的阶乘值

2. 要求：输入一个整型数（不超过10），求出其阶乘值后输出，求阶乘的算法用子程序来实现。

3. 提示：可以用递归来实现，也可以用简单的循环来实现。

这里使用循环来实现：

对于汇编新手，最好通过高级语言的编程测试，然后再写汇编代码，这样效果会好一些、

求阶乘的C++代码如下：

 1 //The program is to find the factorial from 1 to 10

 2 //author:Karllen

 3 //Date:  05/21/2014

 4 

 5 #include <iostream>

 6 

 7 int factorial(int n);

 8 

 9 int main()

10 {

11     int n;

12     std::cin>>n;

13     std::cout<<factorial(n)<<std::endl;

14 

15     system("pause");

16     return 0;

17 }

18 

19 int factorial(int n)

20 {

21     int sum = 1;

22     while (n!=1)

23     {

24         sum*=n;

25         --n;

26     }

27     return sum;

28 }

汇编代码如下：

 1 ; Example assembly language program -- adds two numbers

 2 ; Author:  Karllen

 3 ; Date:    revised 05/2014

 4 

 5 .386

 6 .MODEL FLAT

 7 

 8 ExitProcess PROTO NEAR32 stdcall, dwExitCode:DWORD

 9 

10 INCLUDE io.h            ; header file for input/output

11 

12 cr      EQU     0dh     ; carriage return character

13 Lf      EQU     0ah     ; line feed

14 

15 .STACK  4096            ; reserve 4096-byte stack

16         

17 .DATA                   ; reserve storage for data

18         prompt   BYTE "The program is to find the factorial from 1 to 10",cr,Lf,0

19         numInput BYTE "Please enter a number from 1 to 10",cr,Lf,0

20         answer   BYTE "The number factorial is"

21         value    BYTE 11 DUP(?)

22                  BYTE cr,Lf,0

23 

24 PUBLIC _start         

25 .CODE 

26 _start:

27                                 ; start of main program code

28         output prompt 

29         

30         doInput:

31            output numInput

32            input  value,11

33            atod   value

34            cmp    eax,1

35            jl     doInput

36            cmp    eax,10

37            jg     doInput

38         push   eax

39         call   findFactorial

40         add    esp,4

41         

42         dtoa   value,eax

43         output answer 

44         

45         INVOKE  ExitProcess, 0  ; exit with return code 0

46                   ; make entry point public

47         

48  findFactorial  PROC NEAR32

49                   push ebp

50                   mov  ebp,esp

51                   

52                   mov  eax,[ebp+8]

53                   mov  ebx,eax

54                   cmp  eax,1

55                   je   endFindWhile     

56                   doFindWhile:

57                            dec ebx

58                            cmp ebx,1

59                            je  endFindWhile

60                            mul ebx

61                            jmp doFindWhile

62                   endFindWhile:          

63                   pop  ebp

64                   ret

65    findFactorial  ENDP

66 END                             ; end of source code

测试结果：