用汇编语言实现递归 - 爱吱声

LEN_OF_OUTPUT equ 10* |- U8 _2 R$ w" i5 B4 m
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section .data ;
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userMsg db 'Please enter a single-digit number: ' ;
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lenUserMsg equ $-userMsg ;# u' i# h1 h$ Y# C
disp1Msg db 'The factorial of '
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lenDisp1Msg equ $-disp1Msg ! q4 Y* i: Z* |* z
disp2Msg db ' is '7 [ b% }1 W! a) Z) v3 ~
lenDisp2Msg equ $-disp2Msg
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errMsg db 'Wrong input. Only one-digit number can be accepted.',0x0a# u+ Y) q; E* ]5 i/ o, y
lenErrMsg equ $-errMsg $ J; Y8 ~& t' |
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section .bss ;
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num resb 1 Q5 ]* W* I$ T/ i
result resd 1
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buffer resb LEN_OF_OUTPUT+1
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section .text ;
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global _start2 a* b2 x$ `/ o: C2 \7 `8 q/ U* ~* x
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_start: ;
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mov eax, 4
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mov ebx, 1
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mov ecx, userMsg# z$ D' a4 o4 B+ G! x' U
mov edx, lenUserMsg
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int 80h7 Y, m" Y# E9 z( ^* j$ Y: ~1 b
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; read user's input# t) s9 V' S6 ^4 S
mov eax, 3* Q; y1 i4 t8 I& m- v8 _: {& E
mov ebx, 0. `) a9 y' r) b T
mov ecx, num
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mov edx, 1 ; length of input buffer& J: e* U9 P- \! c3 Q" i
int 80h
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mov eax, [num] a/ \, J9 z* J8 M* P4 A
and eax, 0xFF
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sub eax, 0x305 ^9 J% n7 E, s$ X
jl ERROR7 w$ y* ? d+ a3 v
cmp eax, 10
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jl DO_CALC
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ERROR:
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mov eax, 4
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mov ebx, 1
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mov ecx, errMsg
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mov edx, lenErrMsg) u* B3 Z, O+ T; D$ `
int 80h
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jmp EXIT
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DO_CALC:
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call factorial" p, s+ h* ]( E
; The parameter is in eax. After calling, the result will be stored in eax.6 E$ o) o# _0 X' a0 S, q
mov [result], eax ; Save the result
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; print result6 I& o( E- {$ A) k
mov eax, 4* @, F* p" b. ?! g2 w$ b. Y
mov ebx, 1; U, j: s/ D& ?) ^$ F+ l
mov ecx, disp1Msg
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mov edx, lenDisp1Msg* c9 m1 g8 A, L, ^$ g: q
int 80h
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mov eax, 4( \) ~0 C: q6 J
mov ebx, 1- w/ i" A& ?) t) \0 t5 p) h' U
mov ecx, num
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mov edx, 1
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int 80h $ q/ r P$ `# h
mov eax, 4$ Z K9 i, @- u; @
mov ebx, 1
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mov ecx, disp2Msg
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mov edx, lenDisp2Msg
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int 80h
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; output number
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mov eax, [result] ; VALUE THAT I WANT TO CONVERT AND DISPLAY
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mov byte [buffer+LEN_OF_OUTPUT],0x0a
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lea esi,[buffer+LEN_OF_OUTPUT]
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mov ebx,10
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ASC_LOOP:
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mov edx,0 ; clear dx prior to dividing edx:eax by bx3 K. ^9 \, V s1 L/ D" S+ U% [
div ebx ;DIV EAX/10
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add edx,0x30 ;ADD 48 TO REMAINDER TO GET ASCII CHARACTER OF NUMBER
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dec esi ; store characters in reverse order
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mov [esi],dl
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cmp eax,0
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jz END_ASC ;IF AX=0, END THE PROCEDURE OF NUMBER TO ASCII
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jmp ASC_LOOP ;ELSE REPEAT0 Y; V* e9 F2 G/ v
END_ASC:
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mov eax, 4* @; Q* `& F" ?
mov ebx, 1* S+ t4 {+ k8 @! N: g
mov ecx, esi
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lea edx,[buffer+LEN_OF_OUTPUT+1]
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sub edx, ecx
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int 80h - c2 z \$ K- ?" `% X
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; Exit code
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EXIT:
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mov eax, 1
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mov ebx, 0
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int 80h
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; Factorial function using recursion
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factorial:
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; Check if eax is 0 (base condition)
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cmp eax, 0+ \+ M' B. v. ^5 w% S9 D
jz end_recursion
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; Save the current value of eax
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push eax
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; Decrement eax and call factorial function recursively
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dec eax
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call factorial
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; Multiply the result returned in eax with the saved value of eax
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pop ebx
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imul eax, ebx' I4 [1 L9 T! Z) ]; t
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ret
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end_recursion:
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; Return 1 when eax is 0 (base condition)
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mov eax, 18 P8 d( q* W {7 e8 }% @7 S( o
ret

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nasm -f elf factorial.asm
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ld -m elf_i386 -s -o factorial factorial.o: [( U, a3 ]( o1 t
./factorial; g$ A' R% @1 Z7 e; j, y, g

复制代码

; Factorial function using recursion% ?- G5 T' l4 ~ W F: b2 C
factorial:: @. D5 e$ E! O, X! t7 D
; Check if eax is 0 (base condition)3 `5 r; }7 R; m9 b# |
cmp eax, 0# s& X- a( M5 g) n/ Z
jz end_recursion
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; Save the current value of eax U* c3 K8 ]$ x" `4 Z, g% z
push eax
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; Decrement eax and call factorial function recursively6 V/ w/ S0 Q+ Q
dec eax
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call factorial
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; Multiply the result returned in eax with the saved value of eax; Z. W e) }4 R
pop ebx
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imul eax, ebx) z6 d! \% @) X( `# \
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ret
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end_recursion:
; Return 1 when eax is 0 (base condition)) r7 T3 a0 v9 z4 D7 P
mov eax, 13 c* T' K$ X6 O0 T
ret

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