计算机原理MCS习题答案

MCS_8086习题4答案：

1. 从屏幕上输入大写字母，转换为小写字母并输出

要求：程序具有可读性、容错性 data segment para

str1 str2 str3

db 0dh, 0ah, ‘Please input(a-z): $’ db 0dh, 0ah, ‘The input is error!$’ db 0dh, 0ah, ‘The result is: $’

data ends

ss_seg segment stack

dw

100 dup(0)

ss_seg ends code segment para

assume cs:code, ss:ss_seg, ds:data main proc far

mov mov

ax, data ds, ax dx, str1 ah, 9 21h ah, 1 21h al, ‘A’ error al, ‘Z’ error next dx, str2 ah, 9 21h

1

main1: lea

mov int mov int cmp jb cmp ja jmp

;显示提示信息

;输入小写字母

;判断输入字符是否为’a’~’z’

error: lea

mov int

;显示错误提示信息

jmp main1 al, 20h

;跳转，重新输入

next: sub

push ax lea mov int pop mov mov int mov int

dx, str3 ah, 9 21h ax dl, al ah, 2 21h ax, 4c00h 21h

;返回操作系统

;显示转换后的大写字母

;显示输出提示信息

main endp

code ends

end main

2. 编写一子程序asc2bin，将ASCII转换为二进制数

要求： 输入参数：AL中存放需要转换的ASCII

输出参数：AL中存放转换后的二进制数并返回

;功能：将ASCII转换为二进制数 ;输入参数：AL中存放需要转换的ASCII ;输出参数：AL中存放转换后得到的二进制数 asc2bin

sub cmp jbe sub

proc al, 30h al, 9 asc2bin_1 al, 7

asc2bin_1: ret asc2bin

2

endp

3. 内存中存放8个16位有符号数，求8个数值之和，并将结果存放在内存变

量SUM中

注：程序中应用到字扩展为双字的指令CWD data segment para

buf sum

dw dd

-1, 30000, 35000, 36000, 37000, 20000, 10000, -2 0

data ends

ss_seg segment stack

dw

100 dup(0)

ss_seg ends code segment para

assume cs:code, ds:data, ss:ss_seg main proc far

mov mov lea mov

ax, data ds, ax bx, buf cx, 8 ax, [bx]

;有符号数字扩展为双字 ;32位数相加

;bx指向buf首地址

main1: mov

cwd add adc inc inc loop mov int

word ptr sum, ax word ptr sum + 2, dx bx bx main1 ax, 4c00h 21h

;循环8次

main endp

code ends

end main

3

4. 内存中存放8个8位有符号数，请按从大到小顺序排列

data segment para

buf

db

-1, 30, 35, 36, 37, 20, 100, -2

data ends

ss_seg segment stack

dw

100 dup(0)

ss_seg ends code segment para

assume cs:code, ds:data, ss:ss_seg main proc far

mov mov mov

ax, data ds, ax cx, 8 bx, 0 di, 0

;外循环

main1: mov

mov

push cx

al, buf[bx] al, buf[bx+1] next

;不符合规则, 则交换数据

;内循环

main2: mov

cmp jge

xchg al, buf[bx+1] mov mov

buf[bx], al di, 1 bx main2 cx di, 0 exit main1 ax, 4c00h

next: inc

loop pop cmp jz loop mov

;判断内循环是否发生数据交换

exit:

4

int 21h

main endp

code ends

end main

5. 内存中有8个16位数，请编写程序将8个数倒序排放

例：定义内存中8个数

buf dw 100, 3, 1, 20, 40, -2, 7, 10

10, 7, -2, 40, 20, 1, 3, 100

程序运行后，buf开始应为：buf dw

data segment para

buf

dw

-1, 30000, 35000, 36000, 37000, 20000, 10000, -2

data ends

ss_seg segment stack

dw

100 dup(0)

ss_seg ends code segment para

assume cs:code, ds:data, ss:ss_seg main proc far

mov mov mov mov

ax, data ds, ax bx, 0 cx, 8

main1: push buf[bx]

inc inc loop lea mov

bx bx main1 bx, buf cx, 8 [bx] bx bx

5

;8个数依次入堆栈

main2: pop

inc inc