汇编第五章课后题答案

1.从屏幕上输入小写字母，转化为大写字母输出

(解法1)

DATA SEGMENT

MESSAGE DB "ENTER A STRING:",0AH,0DH,'$' MAXLENGTH DB 50,?,50 DUP(?) ;每次最多可以输入49个字符DATA ENDS

CODE SEGMENT

ASSUME DS:DATA,CS:CODE

START:

MOV AX,DATA

MOV DS,AX

LEA DX,MESSAGE ;输出ENTER A STRING

MOV AH,09H

INT 21H

LEA DX,MAXLENGTH ;输入字符串

MOV AH,0AH ;键盘输入到缓冲区,DS:DX=缓冲区首址

INT 21H ;(DS:DX)=缓冲区最大字符数,(DS:DX+1)=实际输入的字符数

MOV AH,02H ;输出回车换行

MOV DL,0AH

INT 21H

MOV AH,02H

MOV DL,0DH

INT 21H

MOV CL,MAXLENGTH+1;把字符的实际长度放入寄存器CL

MOV CH,0

MOV BH,02H

LEA SI,MAXLENGTH+2;取字符串的基地址放入SI

XUN:

MOV AL,[SI]

CMP AL,'Z'

JBE S1 ;小于等于'Z'转移

JMP S3

S1:CMP AL,'A'

JAE DA ;大于等于'A'转移

JMP OUTPUT

DA:ADD AL,20H

JMP OUTPUT

S3:CMP AL,'z' ;小于等于小Z转移

JBE S4

S4:CMP AL,'a' ;大于等于小a转移

JAE XIAO

JMP OUTPUT

XIAO:

SUB AL,32

JMP OUTPUT

OUTPUT:

MOV DL,AL

MOV AH,02H ;显示输出

INT 21H

INC SI

LOOP XUN

MOV AH,4CH

INT 21H

CODE ENDS

END START

(解法2)

;将输入的小写字母转化为大写字母输出，输入回车结束CODE SEGMENT

ASSUME CS:CODE

BEGIN:

MOV AH,01H

INT 21H

CMP AL,0DH ;ASCII OF CARRIAGE RETURN

JE EXIT

CMP AL,61H ;ASCII OF 'a'

JB STOP

CMP AL,7AH ;ASCII OF 'z'

JA STOP

SUB AL,20H

STOP:

MOV DL,AL

MOV AH,2

INT 21H

JMP BEGIN

EXIT:

MOV AH,4CH

INT 21H

RET

CODE ENDS

END BEGIN

2.输入一个字符,找出它的前导字符和后续字符,并按顺序显示这三个字符.

(解法1)

CODE SEGMENT

MAIN PROC FAR

ASSUME CS:CODE

START:

PUSH DS

XOR AX,AX

PUSH AX

MOV AH,01H

INT 21H

CMP AL,61H

JB EXIT

CMP AL,7AH

JA EXIT

MOV CL,AL

DEC AL

MOV DL,AL

MOV AH,02H

INT 21H

MOV DL,CL

MOV AH,02H

INT 21H

AND AL,01H

INC CL

MOV DL,CL

MOV AH,02H

INT 21H

EXIT:

MOV AX,4C00H

INT 21H

RET

MAIN ENDP

CODE ENDS

END START

(解法2)

.MODEL SMALL

.STACK 200H

.DATA

imsg db 'Input:$' ;输入提示信息

omsg db 0Dh,0Ah,'Output:$' ;输出提示信息string db 3 dup(0),'$' ;存放三个字符

.CODE

START:

mov ax,@data

mov ds,ax

lea dx,imsg

mov ah,9

int 21h

mov ah,1

int 21h

lea di,string

dec al

mov cx,3

s:

mov [di],al

inc di

inc al

loop s

lea dx,omsg

mov ah,9

int 21h

lea dx,string

mov ah,9

int 21h

MOV AH,07H

INT 21H

MOV AX,4C00H

INT 21H

END START

3.将AX寄存器中的16位数分成4组,每组4位,然后把这四组数分别放在AL,BL,CL,DL中

.MODEL SMALL,C

.CODE

.STARTUP

MOV AX,3456H

MOV BX,AX

MOV CL,4

ROL AX,CL

MOV BX,AX

AND AL,0FH ;AL中是15,14,13,12

ROL BX,CL

MOV DX,BX

AND BL,0FH ;BL中是11,10,9,8

AND AH,0FH

MOV CH,AH ;CH中是7,6,5,4

MOV CL,CH

AND DH,0FH ;DH中是3,2,1,0

MOV DL,DH

.EXIT 0

END

4.试编写一程序,要求比较两个字符串STRING1和STRING2所含字符是否相同,若相同则显示'MATCH',若不相同则显

示'NOT MATCH'.

.MODEL SMALL

.DATA

STRING1 DB "LDSKFJSLDKF"

LENG1 EQU $-STRING1

STRING2 DB "LDSKFJSLDKP"

LENG2 EQU $-STRING2

MSG1 DB "MATCH",24H

MSG2 DB "NOT MATCH",24H

.CODE

MOV AX,@DATA

MOV DS,AX

MOV ES,AX

MOV BX,LENG1

MOV CX,LENG2

CMP BX,CX

JNZ NOT_MATCH

LEA SI,STRING1

LEA DI,STRING2

CLD

REPZ CMPSB

JZ _MATCH

NOT_MATCH:

LEA DX,MSG2

MOV AH,09H

INT 21H

JMP _EXIT

_MATCH:

LEA DX,MSG1

MOV AH,09H

INT 21H

_EXIT:

MOV AH,07H

INT 21H

MOV AX,4C00H

INT 21H

END

5.要求能从键盘接收一个个位数,然后响铃N次(响铃的ASCII码为07) .MODEL SMALL

.DATA

MSG DB "YOUR INPUT IS NOT 1-9!",24H .CODE

.STARTUP

MOV AH,0

INT 16H ;接收一个键盘输入

CMP AL,31H

JB ERROR

CMP AL,39H

JA ERROR

MOV CL,AL

SUB CL,30H

CYCLE:

MOV DL,7

MOV AH,09H

INT 21H

MOV AH,07H ;按一下键就响一下铃声

INT 21H

LOOP CYCLE

JMP _EXIT

ERROR:

LEA DX,MSG

MOV AH,09H

INT 21H

MOV AH,07H

INT 21H

_EXIT:

.EXIT 0

END

6.编写程序,将一个包含有20个数据的数组M分成两个数组,正数数组P 和负数数组N,并分别把这两个数组中数据的

个数显示出来.

.MODEL SMALL,C

.DATA

INDEX DB 12,-20,4,05H,11H,2AH,-11,2,3,09H

DB -3,0,-9,44H,32H,33H,34H,-5,40H,22H

P DB 0,20 DUP(0) ;存放正数

N DB 0,20 DUP(0) ;存放负数

.CODE

DISPLAY PROC NEAR USES AX

AND AH,0FH

.IF AH>= 0AH && AH<= 0FH

ADD AH,07H

.ENDIF

ADD AH,30H

MOV DL,AH

MOV AH,02H

INT 21H

MOV AH,07H

INT 21H

RET

DISPLAY ENDP

.STARTUP

LEA DI,P+1

LEA SI,N+1

LEA BX,INDEX

MOV CX,14H

CYCLE:

CMP BYTE PTR [BX],0

JG NOSIGN

INC AL ;AL中存放负数

MOV DL,BYTE PTR [BX]

MOV BYTE PTR DS:[DI],DL

INC DI

INC BX

LOOP CYCLE

NOSIGN:

INC AH ;AH中存放正数

MOV DL,BYTE PTR [BX]

MOV BYTE PTR DS:[SI],DL

INC SI

INC BX

LOOP CYCLE

MOV P,AH

MOV N,AL

CALL DISPLAY

MOV AH,AL

CALL DISPLAY

.EXIT 0

END

7.试编制一个汇编语言程序,求出首地址为DATA的100D字数组中的最小偶数,并把它存放在AX中.

datarea segment

data dw 10,2,4,8,7,7,69,65,55,89,95

dw 25,39,77,88,25,1,47,88,8,8,77,88,22 count=($-data)/2

num dw 0ffeeh

datarea ends

code segment

main proc far

assume cs:code,ds:datarea

push ds

mov ax,0

push ax

begin:

mov ax,datarea

mov ds,ax

mov bl,2

mov cx,count

lea si,data

A:

mov ax,[si]

mov dx,ax

div bl

cmp ah,0

jne circle

cmp dx,num

jb B

circle:

add si,2

lopa:

loop A

exit:

mov ax,num

ret

B:

mov num,dx

jmp lopa

main endp

code ends

end

8.把AX中存放的16位二进制数K看作是8个二进制的"四分之一字节".试编写一程序,要求数一下值为3(即11B)的四

分之一字节数,并将该数在终端上显示出来.

MOV CX,8

MOV DL,0

NEXT3：ROR AX，1

JNC NEXT1

ROR AX，1

JNC NEXT2

INC DL

NEXT2：LOOP NEXT3

ADD DL, 30H

MOV AH, 2

INT 21H

MOV AH, 4CH

INT 21H

NEXT1：ROR AX, 1

JMP NEXT2

9.试编写一汇编语言程序,求出首地址为DATA的100D字数组中的最小偶数,并把它存放在AX中.

.MODEL SMALL,C

.DATA

_DATA DW 100 DUP(?)

.CODE

.STARTUP

LEA SI,_DATA

MOV AX,[SI]

MOV CX,100

CYCLE:

ADD SI,2

.IF AX< [SI]

MOV AX,[SI]

.ENDIF

LOOP CYCLE

.EXIT 0

10.设有一段英文,其字符变量名为ENG,并以$字符结束,试编写一程序,查对单词SUN在该文中的出现次数,并以格式

"SUN****"显示出次数.

.MODEL SMALL

.386

.DATA

ENG DB 'SUN','SUN JAVA',24H

MESSAGE DB 'SUN:','$' .STACK 100H

.CODE

MAIN PROC FAR START:

PUSH DS

AND AX,0

PUSH AX

MOV AX,@DATA

MOV DS,AX

MOV AX,0H

MOV SI,1H

SUBSI1:

SUB SI,1H

SUBSI2:

SUB SI,1H COMPARES:

ADD SI,1H

MOV DL,ENG[SI]

CMP DL,24H

JE PRINT

CMP DL,53H

JNE COMPARES COMPAREU:

ADD SI,1H

MOV DL,ENG[SI]

CMP DL,55H

JNE SUBSI2 COMPAREN:

ADD SI,1H

MOV DL,ENG[SI]

CMP DL,4EH

JNE SUBSI1

INC AX

JMP COMPARES

PRINT:

LEA DX,MESSAGE

PUSH AX

MOV AH,09H

INT 21H

POP AX

CALL SHOWNUMBER EXIT:

RET

MAIN ENDP SHOWNUMBER PROC NEAR COVERNUM:

DAA

MOV DX,AX

MOV CL,4H

SHOW:

ROL DX,4H

PUSH DX

AND DX,0FH

ADD DX,30H

MOV AH,02H

INT 21H

POP DX

LOOP SHOW

RET

SHOWNUMBER ENDP

END START

11.从键盘输入一系列以$为结束符的字符串,然后对其中的非数字字符计数,并显示出计数结果.

.MODEL SMALL

.386

.CODE

MAIN PROC FAR

START:

PUSH DS

MOV AX,0

PUSH AX

MOV CX,0

INPUT:

MOV AH,1H

INT 21H

COMPARE:

CMP AL,24H

JE PRINT

CMP AL,30H

JL ADDCOUNT

CMP AL,39H

JG ADDCOUNT

ADDCOUNT:

ADD AX,1H

JMP INPUT

CALL SHOWNUMBER

EXIT: RET

MAIN ENDP

SHOWNUMBER PROC NEAR

COVERNUM:

DAA

MOV DX,AX

MOV CL,2H

SHOW:

ROL DL,4H

PUSH DX

AND DL,0FH

ADD DL,30H

MOV AH,02H

INT 21H

POP DX

LOOP SHOW

RET

SHOWNUMBER ENDP

END START

12.有一个首地址为MEM的100D字数组,试编制程序删除数组中所有为零的项,并将后续项向前压缩,最后将数组的剩

余部分补上零.

.model small

.386

.stack 100H

mem dw

12,0,0,0,0,0,1,2,3,6,4,7,8,2,1,0,0,54,5,0,2,4,7,8,0,5,6,2,1,4,8,5,1,45,7 ,5,1,2,0,2,4,0,2,54,0,12,0,

0,0,0,0,1,2,3,6,4,7,8,2,1,0,0,54,5,0,2,4,7,8,0,5,6,2,1,4,8,5,1,45,7,5,1, 2,0,2,4,0,2,54,0,45,7,5,1,2

,0,2,4,0,2

.code

MAIN PROC FAR

start:

push ds

and ax,0

push ax

mov ax,@data

mov ds,ax

mov ax,0H

mov bx,64H

mov cx,64H

mov si,0FFFEH

repeat:

ADD si,2H

cmp MEM[si],0H

JE calls

loop repeat

calls:

INC ax

call sort

cmp ax,1H

JE lastValue

DEC cx

jmp repeat

exit :

ret

lastValue:

mov mem[bx],0H

DEC cx

jmp repeat

MAIN ENDP

sort PROC NEAR

push cx

push si

sub si,2H

s:

add si,2H

mov dx,mem[si]

mov mem[si+2],dx

loop s

return:

pop si

pop cx

ret

sort ENDP

END start

13.在STRING到STRING+99单元中存放着一个字符串,试编制一程序测试该字符串中是否存在数字.如有,则把CL的第