这里的任何人都可以让我了解这个程序，我将通过它获得什么输出?

Question

DATA SEGMENT
STRING1 DB 11H,22H,33H,44H,55H
MSG1    DB "FOUND$"
MSG2    DB "NOT FOUND$"
SE      DB 34H
DATA ENDS
PRINT MACRO MSG
MOV AH, 09H
LEA DX, MSG
INT 21H
INT 3
ENDM
CODE SEGMENT
ASSUME CS:CODE, DS:DATA
START:
MOV AX, DATA
MOV DS, AX
MOV AL, SE
LEA SI, STRING1
MOV CX, 04H
UP:
MOV BL,[SI]
CMP AL, BL
JZ FO
INC SI
DEC CX
JNZ UP
PRINT MSG2
JMP END1
FO:
PRINT MSG1
END1:
INT 3
CODE ENDS
END START

Answer 1

程序在序列 11H，22H，33H，44H 中搜索字节 '34H'。

"开始"部分执行以下操作：

• 将 DS：SI 设置为 STRING1 的地址。
• 为要搜索的字节设置 AL 为。
• 为 CX 设置要在STRING1内搜索的字节数 (4 字节)。

循环部分执行以下操作：

• 将 DS：SI 处的字节(从 STRING1 开始)加载到 BL 中
• 将其与要搜索的字节进行比较(以AL为单位)
• 如果字节相等(零标志 = 1)，则打印"已找到">
• 否则(不相等)转到下一个字节(INC SI)，递减计数器(CX)
• 如果计数器为零，则退出循环并打印"未找到">

---

打印宏：

MOV AH, 09H
INT 21H 

是 MS-DOS 对打印的调用，直到"$"INT 3表示退出程序。

计数器 CX 设置为 4 但STRING1序列包含 5 个字节是可疑的。如果没有真正调试程序，我会说CX = 5是正确的吗？

Answer 2

我的投票相当于memchr(s,c,n)，其中s在SI中(每次迭代递增)，c在BL中(与从 SI 获得的"项目找到"退出条件的东西相比)，n在CX中(如果数组元素等于BL未找到，则递减为零，这是其他退出条件)加上友好的输出(包含 int21h 调用的宏)。见 http://man7.org/linux/man-pages/man3/memchr.3.html

Answer 3

它在字节数组中搜索33h的值11H,22H,33H,44H,55H

DATA SEGMENT
# Data where we will look up for value
STRING1 DB 11H,22H,33H,44H,55H
# message to be printed out
MSG1 DB "FOUND$"
# yet one message
MSG2 DB "NOT FOUND$"
# program will look up for this value
SE DB 33H
DATA ENDS
# this is PRINT macro- will be used later like a function
PRINT MACRO MSG
# 09H - is a function of interrupt 21h - print to console http://spike.scu.edu.au/~barry/interrupts.html
MOV AH, 09H
LEA DX, MSG
# print message using interrupt 21h
INT 21H
# I think it's exit - check it in the x86 interrupts table if you need
INT 3
ENDM # end of print macro
CODE SEGMENT
ASSUME CS:CODE, DS:DATA
START:
# this is the first line of code
MOV AX, DATA
MOV DS, AX
# copy value of SE (33h) to the AL register so later we can compare it
MOV AL, SE
LEA SI, STRING1
# save in CX length of the data to be looked up for value (actually num or iterations)
MOV CX, 04H
# the main loop starts here
UP:
# copy byte from buffer STRING1 to the BL register
MOV BL,[SI]
# check if AL==BL -> value found
CMP AL, BL
# if AL==BLjump to FO (will print FOUND)
JZ FO
# if not found, 
# move to next byte in STRING1
INC SI
# decrement loop constraint (loop should end before reaching end of string)
DEC CX
# if CX <> 0 loop again
JNZ UP
# if CX==0 print message NOT FOUND
PRINT MSG2
JMP END1
FO:
PRINT MSG1
END1:
INT 3
CODE ENDS
END START