Structure your work



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Structure your work

On drive M in your assembly directory, create a directory called week4.


Write programs called WEEK4A.ASM through to WEEK4B.ASM as below and save them to the WEEK4 directory.
NB:

After assembling and linking WEEK4A and WEEK4B, examine each program in the debugger.

e.g.
TD WEEK4A (will open the debugger and go through the code in week4a.exe)
(While in the debugger, pressing the F7 key will step through each line in your

program).


WEEK4A.ASM


Write an 8086 assembly language program to do the following:

  • Move 20h into ax

  • Move 30h into bx

  • Swap the contents of ax and bx (using no more than 3 mov instructions)



WEEK4B.ASM

Write an 8086 assembly language program to do the following:



  • Move 20h into ax

  • Move 30h into bx

  • Swap the contents of ax and bx (using no more than 1 xchg instruction).


WEEK4C.ASM

Key in the program below.


What value will you see in the debugger for ax after the first 3 instructions have exectued? – Check your answer by using the debugger.
Determine the value will you see in the debugger for bx after the first 3 instructions have exectued? – Check your answer by using the debugger.
Which is the source operand - ax or bx?

Which is the destination operand - ax or bx?

title week4c.asm

.model small

.stack 100h

.data


.code

mov ax,4


mov bx,5

add bx,ax


mov ax, 4C00h ; Terminate program

int 21h ; correctly

end


WEEK4D.ASM


title week4D.asm

.model small

.stack 100h

.data

.code


mov ax,5

mov bx,5


add ax,bx
mov ax, 4C00h ; Terminate program

int 21h ; correctly

end

What value will you see in the debugger for ax after the first 3 instructions have exectued? – Check your answer by using the debugger.


Determine the value will you see in the debugger for bx after the first 3 instructions have exectued? – Check your answer by using the debugger.

Exercise

Write down the hex values for each uppercase character from A through to Z.

The first two characters and the last character have been completed for you in the table below.
After you have completed the table on paper, check your answer on the internet.

Did you get it right – if not where did you go wrong?



Character ASCII Value – expressed in Hexadecimal
A 41

B 42


.

.

.



Z 5A

WEEK4E.ASM

Take the program below and work out on paper what is in each of the registers after each instruction is executed. – The first 2 instructions have been completed for you in Table A below.


After you have completed the table – check your answer using the debugger (td.exe).
What does the program print out when you run it?



Line No.




1

mov ah,02h ;

2

mov dl,43h ; 3 lines to print capital C

3

int 21h ;







4

sub dl,2 ; subtract 2 from value stored in dl

5

int 21h ; call os







6

add dl,17 ; add 2 to the value stored in dl

7

int 21h ; call os

The complete program is given below:

title week4E.asm

.model small

.stack 100h

.data


.code

mov ah,02h ;

mov dl,43h ; 3 lines to print capital C

int 21h ;


sub dl,2 ; subtract 2 from value stored in dl

int 21h ; call os


add dl,17 ; add 17 to the value stored in dl

int 21h ; call os


mov ax, 4C00h ; Terminate program

int 21h ; correctly

end


Table A


 

1

2

3

4

5

6

7

AX

0200

0200

02??













BX

0000

0000




 

 

 

 

CX

0000

0000




 

 

 

 

DX

0000

0043




 

 

 

 



WEEK4F.ASM

The program from week4E.asm printed the letters CAR. Note that only two mov instructions were used.


Complete the program by printing the letters CARLOW. – Do not add any mov instructions to the program than are already there.
The program will print CARLOW. It will have only two mov instructions.

Loop Exercises 1




WEEK4G.ASM


Write a loop to print all 26 uppercase letters (A through Z).

Program Output:

ABCDEFGHIJKLMNOPQRSTUVWXYZ



WEEK4H.ASM


Write a loop to print all 26 lowercase letters in descending order:

Program Output:

zyxwvutsrqponmlkjihgfedcba


WEEK4I.ASM


Write a loop to print the digits 9 through to 0

Program Output:

9876543210




WEEK4J.ASM


Write a loop to print the following

Program Output:

ABCDEFGHIJKLMNOPQRSTUVWXYZ

zyxwvutsrqponmlkjihgfedcba


WEEK4K.ASM


Write a loop to print ‘A’ 26 times.

Type in this program and get it to run.




WEEK4L.ASM


Write a program that takes in a single character.

Assume the character entered is a digit, n, in the range 1-9.


Print the first n digits.

E.g. user keys in 0 – Program Prints Out 0

E.g. user keys in 1 – Program Prints Out 01

E.g. user keys in 2 – Program Prints Out 012

E.g. user keys in 3 – Program Prints Out 0123

E.g. user keys in 4 – Program Prints Out 01234

E.g. user keys in 5 – Program Prints Out 012345

.

.



E.g. user keys in 9 – Program Prints Out 0123456789
You are to use one loop in your program.


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