[assembly language practice] (II). Write a program to calculate the value of expression w=v- (x+y+z-51) (including code and process screenshots)

Preface

How do you do , I am a “ blame & ”, I'm a college student .
Home link ： blame & My personal blog home page
️ The main direction of the blog is ： Course learning knowledge 、 Homework problem solving 、 Final exam preparation . With the deepening of specialty, it will become more and more extensive … Look forward to .
️ One “ I don't want what I didn't do well to be your regret ” Bloggers .
Nice to meet you , Come on together ！

If you are not familiar with assembly instructions, you can see my article ：【 Assembly language practice 】（ One ）、 The code knocked out in the first experiment and the explanation of common instructions （ Assembly language 4 edition , Wang Shuang , Super detailed notes ）

One 、 subject

• Experimental content ： Write a program to calculate the expression ｗ=v-（ｘ+ｙ+ｚ-51） Value .
• The experimental requirements ：
  1、 Variable x,y,z,v, The value of is a number in memory ;
  2、 Will use debug In debugging , Modify variables x,y,z,v Value ;
  3、 The result of the calculation is saved in the variable w in , The initial value is 0.

Two 、 Code

notes ： Assembly language programming is not case sensitive

DATAS SEGMENT
	x DW 5	; Set variables and assign initial values 
	y DW 5
	z DW 5
	v DW 5
	W DW 0
DATAS ENDS

STACKS SEGMENT
	; Enter the stack segment code here 
STACKS ENDS

CODES SEGMENT
	ASSUME CS:CODES,DS:DATAS,SS:STACKS
START:
	MOV AX,DATAS
	MOV DS,AX
	
	MOV CX,0		;CX=0
	MOV AX,X		;AX=X
	ADD AX,Y		;AX=X+Y
	ADD AX,Z		;AX=X+Y+Z
	SUB AX,51		;AX=X+Y+Z-51
	MOV BX,V		;BX=V
	SUB BX,AX		;BX=V-(X+Y+Z-51)
	MOV CX,BX		;CX=V-(X+Y+Z-51)
	MOV W,CX		;W=V-(X+Y+Z-51)
	
	MOV AH,4CH
	INT 21H
CODES ENDS
	END START

3、 ... and 、 Operation flow chart

1、 Don't change xyzv Operation of initial value

Analysis of operation results ：

• ｗ=v-（ｘ+ｙ+ｚ-51） take x=y=z=v=5 Brought in ,w=41
• Because will w Value deposit CX,CX In the end, it's equal to 0029, Hexadecimal 0029 Convert to decimal 2*16+9=41
• So the calculation is correct

2、 modify xyzv Operation of initial value

notes ： It's execution （ The following codes work ： That is, initialize variables ）

MOV AX,DATAS
MOV DS,AX

Then execute （ The following codes work ： Change the value of the variable ）

-e 143f:0 0 0 0 0

Analysis of experimental results ：

• take x=y=z=v=0, ｗ=v-（ｘ+ｙ+ｚ-51） Brought in ,w=51
• Running results w=CX=0033, Hexadecimal 0033 Convert to decimal to ：3*16+3=51
• So the calculation is correct

Four 、 The understanding of variables

Take the operation without changing the initial value as an example ：
There is still one graph after the four graphs given above ：

• Data register DS=143F

• Variables set in the code ：X,Y,Z,V,W Stored in... In turn 143F:00 In memory at the beginning

• Storage compliance “ Gaogao village, Gaogao village , Low save low ”

• DW： word ,DB: byte ; A word is two bytes ,143D:0000 For a byte
  for example ：
  143F:0000 Deposited 05,143F:0001 Deposited 00, When combined, what is saved is 0005 That is, the first variable X The initial value of the 5
  143F:0002 Deposited 05,143F:0003 Deposited 00, When combined, what is saved is 0005 That is, the first variable Y The initial value of the 5
  By analogy

So we can use the following code , Separate to change X,Y,Z,V Value

-e 143f:0 0 0 0 0

️️️ Don't forget the romantic duck when you are busy Typing Code ！