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Friday, February 21, 2014
ASSUME DS: DATA, CS: CODE
DATA SEGMENT ; start of data
segment
CHAR DB ? ;Byte variable is
not initialized, and used later.
MSG1 DB 0DH, 0AH, 'ENTER A CHARECTER : ','$' ;MSG1 array contains the message
MSG2 DB 0DH, 0AH, 'ASCII EQUIVALENT IS : ','$' ;MSG2 array contains the message.
DATA ENDS ; end of data
segment.
DISPLAY MACRO
ASCI ;
Macro
definition starts here
MOV DL, ASCI ; Ascii
code to be displayed is moved to DL
AND DL, 0F0H ; Mask the lower nibble stored in DL
MOV CL, 04H ; counter to rotate 4 times.
ROR DL, CL ;
Rotate DL contents right 4 bit positions
CMP DL, 09H ; compare
the number stored in DL with 09
JBE NEXT ; if the number
is <= 9 then go to NEXT location
; and add 30H to
that number
ADD DL, 07H ;
otherwise, first add 07H to that number and
NEXT
: ADD DL,30H ; then add 30H to
that number
MOV AH, 02H ; service number to display a character on
the
; monitor ( upper
digit of the ASCII code is displayed)
INT 21H ; using
DOS interrupt
MOV DL, ASCI ; Ascii
code to be displayed is moved to DL
AND DL, 0FH ; Mask the higher nibble stored in DL
CMP DL, 09H ;compare the
number stored in DL with 09
JBE AGAIN ;if the number is
<= 9 then go to AGAIN location
; and add 30H to that number, & then
display
AGAIN: ADD DL, 30H ; then add 30H to
that number & then display.
MOV AH, 02H ; service number to display a character on
the
; monitor ( lower
digit of the ASCII code is displayed)
INT 21H ; using DOS interrupt 21H
ENDM ;
End
of Macro definition
CODE SEGMENT ; start of code
segment
START:
MOV AX, DATA
MOV DS, AX ; initialize data
segment
MOV DX, OFFSET MSG1 ; address of string to be display
MOV AH, 09H ; service number
to display string
INT 21H ; MSG1 is printed
on screen
MOV AH, 01H ;service
number to read a character from keyboard
INT 21H ;
DOS
interrupt is invoked, so that a character is read
; from the keyboard.
MOV CHAR, AL ; user entered character’s ASCII code is
moved
; to CHAR
variable
MOV
AH, 07H ; service number to clear the screen
MOV AL, 00H ; Number of lines to scroll; 00 blank
screen
MOV BH, 0FH ; attribute of character; 0F white and 00
black
MOV CX,
00H ; CH=00 Y coordinate of upper left corner
and
; CL=00 X
coordinate of upper right corner
MOV DH, 39H ; Number of rows; Lower right row
MOV DL, 79H ; Number of columns; lower right column
INT
10H ; BIOS interrupt to clear the screen is
invoked.
MOV
AH, 02H ; service number to set the cursor
MOV BH, 00 ; Page number
MOV DH, 09H ; store row number in DH
MOV DL, 04H ; store the column number in DL register
INT 10H ; BIOS interrupt to set the cursor is
invoked.
MOV DX, OFFSET MSG2 ; store the address of string to display
in DX
MOV AH, 09H
INT 21H ; DOS interrupt
to display the string MSG2
DISPLAY
CHAR ; invoke DISPLAY
macro to print the ASCII code
MOV AH,4CH ; service number to terminate the program
INT 21H ; call the interrupt
CODE ENDS ; end of code segment
END START ; end of program
Output:
D:\MASM>
Masm 4a.asm;
D:\MASM>
Link 4a.obj;
D:\MASM>
4a.exe
OR
D:\MASM>
TD 4a.exe
Then press F7 to trace the program (line by line execution).
ASSUME
DS: DATA,
CS: CODE
DATA SEGMENT ;
start of data segment
LIST
DB
12H,10H,04H,08H ; n
(4) number of elements stored in a LIST array
COUNT
DB 03H ; n-1
counter value stored in COUNT variable
DATA
ENDS ;
end
of data segment
CODE
SEGMENT ;
start
of code segment
START : MOV
AX, DATA ;
initializing the data segment
MOV DS, AX
XOR AX, AX ; clear
AX register content
MOV CL, COUNT ; store n-1 value (3) in CL register (outer loop count)
BACK2: MOV SI, OFFSET
LIST ; set the pointer to the 1st
location of LIST array
MOV BL, CL ; temporally
store the n-1 value in BL register (inner loop count)
BACK1: MOV AL, [SI] ;
get the 1st array element, ie. LIST [0]
to AL
INC SI ;
increment
the pointer by 1 to point to the next location
; ie: LIST[SI+1]
CMP AL, [SI] ; compare
AL with LIST[SI+1]
JB NEXT ;
if 1st
element is less than 2nd element then go to NEXT to
;
decrement the
inner loop count value in BL, to indicate one
;
comparison is
over.
XCHG [SI],
AL ; otherwise swap
the numbers.
MOV [SI-1],
AL
NEXT:
DEC BL ;
decrement
inner loop count value.
JNZ BACK1 ; if inner loop count value is not 0, then go to
BACK1 to
;
repeat the
comparison of remaining elements of LIST array.
LOOP BACK2 ; decrement the outer loop count
value in CL register
; (perform n-1 passes)
MOV AH, 4CH ;
terminate the program
INT 21H
CODE ENDS ;
end
of code segment
END
START
Output:
D:\MASM>
Masm 3a.asm;
D:\MASM>
Link 3a.obj;
D:\MASM>
TD 3a.exe
Then
press F7 to trace the program (line
by line execution).
Click on View
menu and select Dump to see the
output.
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