(Задание 01 курса Assembly Language)

Part I. An Exploration. Not to be handed in.

a) Write a short program that consists of variations of the mov instruction using the different modes

For example:

label1: mov AX,BX
label2: mov BX,AX
label3: mov AX, 5
label4: mov AX,127
label5: mov AX, item
label6: mov item,AX

etc.etc.etc

Assemble your code with the list option and print out the .lst file.

Look at the file to explore how the machine language works. How many bytes in each instruction.? Is there any clear mechanism for generating the op-codes? How are the operands stored in the machine code instructions e.g. in the register mode, immediate mode , direct mode, indirect mode. What are the offsets for the various labels and what does that say about the instruction lengths.

Add a few items to the data section and construct the symbol table. Run the program using the debugger (see the book appendix) and look at the values of the various segment registers.

Part II. To be handed in.

Write a stand-alone assembly language program that inputs two characters using the software interrupt 21 mechanism and calculates the Hamming distance between the two characters.

First, however, in order to get practice using arrays, each character MUST be unpacked into an array of 8 bytes where each byte contains the bit value (either 0 or 1). Then the Hamming distance should be calculated. The Hamming distance is the number of digit positions in which the corresponding digits of two binary patterns of the same length are different. For example, the Hamming distance between 1011101 and 1001001 is two.

After calculating the Hamming difference for a pair of characters, your program should query the user whether he/she wants to enter another pair of characters. If the answer is ‘yes’ (you can use Y/N for ‘yes’ or ‘no’), read and process another character pair. The program terminates only when the user answers ‘no’ to the query.

You should use the I/O macros for all other Input/Output

Submit the following folder via Raven:

Files containing the source code and the executable.
A file containing a Test plan and test data output: For each test case, provide the objective (why you are doing that particular test) and the rationale for selecting the test input. as well as the correct answer from the ASCII table. Zero marks will be given to this part if your assignment provides testing information without this information (i.e., objective and rationale). In particular identify the border cases and test them. Note this file should be clearly annotated so that the T.A. knows exactly what you are showing.
Run at least one run with the sets A,S A,B, 0,1 5,7 A,5 and show the output of your program with this test data . This is not sufficient testing however.
Marking scheme for this assignment (25 marks):
Correctness of the program: 10 marks (if your programs works correctly and your documentation convinces the TA,  don’t expect marks if you just submit a print out of the source code)

Structure and comments: 3 marks (spacing, indentation, comments, variable names etc.)

Good, efficient clear code: 3 marks (weird or convoluted solutions will get zero)

Test plan & test data output: 6 marks (zero marks if no objective and rationale as mentioned above)

Output with class test data: 3 marks

NOTE: To submit your results you must capture the program output in the MS-DOS command window:

1) drag the desired text

2) click on the DOS drop down menu and select edit /copy

3) paste the text into an editor or word processor

Solutions
as2_t.asm

TITLE Assembly_assignment_1
COMMENT |
			program inputs two characters using the software interrupt 21
			mechanism and calculates the Hamming distance between the two characters.
	|

.MODEL SMALL
.STACK 100H
.DATA
prompt_1   	   DB  'Please input a character 1: ',0
prompt_2   	   DB  'Please input a character 2: ',0
prompt_3	   DB  'The hamming distance is: ', 0
quit_msg1      DB  'Do you want to quit (Y/N)?',0

array_1	DB 8 DUP (?) 	; array for first bit pattern
array_2	DB 8 DUP (?)	; ...and second

.CODE
INCLUDE io.mac
.486
main PROC
		.STARTUP

start:
	; work with first character

	PutStr prompt_1			  ;ask to enter character
	mov AH, 01H
	int 21H
	nwln

	mov     AH,80H     		  ; bitmask 10000000
    mov     CX,8 			  ; loop counter
	mov     BX,OFFSET array_1
	mov     DX,1	

print_binary_c1:
        test    AL,AH     		; compare character to bitmask
        jz      byte_0_b1       ; if zero - go to print zero
        PutCh   '1'				; if not zero->it's one->print '1'
		mov [BX], DX			; put 1 into array's element
        jmp     skip1_b1
byte_0_b1:
		dec DX					; make DX=0
		mov [BX], DX			; and store it into array
		inc DX					; make DX 0 again for next iteration
        PutCh   '0'          	; print 0
skip1_b1:
        shr     AH,1  			; shift bitmask to the right
		inc BX					; make BX point to next element in an array
        loop    print_binary_c1   

nwln

	; work with second character

	PutStr prompt_2
	mov AH, 01H
	int 21H
	nwln

	mov     AH,80H
    mov     CX,8
	mov     BX,OFFSET array_2
	mov     DX,1

print_binary_c2:
        test    AL,AH
        jz      byte_0_b2
        PutCh   '1'
		mov [BX], DX
        jmp     skip1_b2
byte_0_b2:
		dec DX
		mov [BX], DX
		inc DX
        PutCh   '0'
skip1_b2:
        shr     AH,1
		inc BX
        loop    print_binary_c2  

		mov CX, 0 ; counter for hamm loop
		mov BX, 0 ; counter for hamming distance
calculate_hamm:
		mov SI, OFFSET array_1
		add SI, CX			; increment adress of array_2 with loop counter
		mov DH, [SI]		; take one byte
		cmp DH, 0			; and compare it to zero
		je bitzero
		; the bit from array_1 is 1, check array_2's bit
		mov SI, OFFSET array_2
		add SI, CX			; increment adress of array_2 with loop counter
		mov DH, [SI]		; take one byte
		cmp DH, 1			; and compare it to one
		je equalbits		; if bytes are equal - jump to equalbits
		inc BX				; if not - increment Hamming distance counter
		inc CX				; increment counter
		cmp CX, 8			; compare it to 8
		jl calculate_hamm	; and jump over again if less

bitzero:				; if byte is zero - take corresponding byte of another array and compare them
		mov SI, OFFSET array_2
		add SI, CX			; increment adress of array_2 with loop counter
		mov DH, [SI]		; take one byte
		cmp DH, 0			; and compare it to zero
		je equalbits		; if bytes are equal - jump to equalbits
		inc BX				; if not - increment Hamming distance counter
		inc CX				; increment counter
		cmp CX, 8			; compare it to 8
		jl calculate_hamm	; and jump over again if less

equalbits: 				; if bytes are equal - increment counter and go to next byte
		inc CX
		cmp CX, 8
		jl calculate_hamm
		nwln
		nwln

		PutStr prompt_3
    	PutInt BX
		nwln

quit_prompt:
		PutStr quit_msg1
		mov AH, 01H
		int 21H
		nwln

		cmp AL, 'y'
		je theend
		cmp AL, 'Y'
		je theend
		cmp AL, 'n'
		je start
		cmp AL, 'N'
		je start
		nwln
		jmp quit_prompt

theend:

	.EXIT
main ENDP
	END main

Part 3
Test

Test output for characters 'A' and 'S':

--------------------------------------------
D:\>as2_t
Please input a character 1: A
01000001
Please input a character 2: S
01010011

The hamming distance is: 2
Do you want to quit (Y/N)?y
--------------------------------------------

Test output for characters 'A' and 'B':

--------------------------------------------
D:\>as2_t
Please input a character 1: A
01000001
Please input a character 2: B
01000010

The hamming distance is: 2
Do you want to quit (Y/N)?y
--------------------------------------------

Test output for characters '0' and '1':

--------------------------------------------
D:\>as2_t
Please input a character 1: 0
00110000
Please input a character 2: 1
00110001

The hamming distance is: 1
Do you want to quit (Y/N)?y
--------------------------------------------

Test output for characters '5' and '7':

--------------------------------------------
D:\>as2_t
Please input a character 1: 5
00110101
Please input a character 2: 7
00110111

The hamming distance is: 1
Do you want to quit (Y/N)?y
--------------------------------------------

Test output for characters 'A' and '5':
--------------------------------------------
D:\>as2_t
Please input a character 1: A
01000001
Please input a character 2: 5
00110101

The hamming distance is: 4
Do you want to quit (Y/N)?y
--------------------------------------------

Решение