1. Defining and processing tables

2. Tables
Defining tables
Searching
Sorting

3. Defining tables MONTH_TBL DB ‘Jan’,’Feb’,Mar’,…,’Dec’
NUMBER_TBL DB 205,208,209,…,210
STOCK_TBL DB 12,’Computer’,
14,’Paper ’,
17,’Diskettes ’

4. TYPE,LENGTH and SIZE
TYPE operator is used to determine the definition.
LENGTH operator is used to determine the number of elements in the table
SIZE operator is used to determine the number of bytes used for this table
E.g: WORD_TABLE DW 12 DUP(?)
Type: 2 bytes
Length: 12
Size: 12*2 = 24 bytes

5. Example RAIN_TBLE DW 12 DUP(?) MOV AX, TYPE RAIN_TBL
MOV BX, LENGTH RAIN_TBL
MOV CX, SIZE RAIN_TBL
(These are not available in EMU8086)

6. SEARCHING A TABLE Example: Give a table: MONTH_TBL DB ’01’,’January ’
DB ’02’, ’February’
DB ’03’, ‘March ‘
Find the entry of the table that equals to MONTH_IN DB ’02’,’February’
LENGTH_INDEX EQU 02
LENGTH_DESCRIPTION EQU 08

7. Searching table (continue)
MOV CX, 03
LEA SI, MONTH_TBL
AGAIN:
MOV AL, MONTH_IN
CMP AL,[SI]
JNE NOTEQUAL
MOV AL, MONTH_IN+1
CMP AL,[SI+1]
JE EQUAL
NOTEQUAL:
JB Exit
Add SI, LENGTH_INDEX
Add SI, LENGTH_DESCRIPTION
Loop Again

8. Searching
Equal:
MOV AH, 09H
LEA DX, prompt
INT 21H

9. Searching tables with string comparisons
Example:
Given MONTH_TBL DB ’001’,’January ’
DB ’002’, ’February’
DB ’003’, ‘March ‘
Find the entry of the table that equals to MONTH_IN DB ’002’
LENGTH_INDEX DB 03
LENGTH_DESCRIPTION DB 08

10. Example MOV CX, 03 LEA DI, MONTH_TBL AGAIN: MOV CX,LENGTH_INDEX
LEA SI, MONTH_IN
REPE CMPSB
JE EqualExit
JB Exit
ADD DI, CX
ADD DI, LENGTH_DESCRIPTION
JMP AGAIN
EqualExit:
MOV AH, 09H
LEA DX, prompt
INT 21H

11. Project 5 .model small, .stack .data para_list label byte
max_len db 50
act_len db ?
input db 50 dup(' ')
para_list2 label byte
max_len2 db 50
act_len2 db ?
input2 db 50 dup(' ')
output1 db "Enter a name:","$"
output2 db "Enter another name:","$"

12. Project 5 .code main proc mov ax,@data mov ds,ax mov es,ax start:
call clearscreen
call getnames
call compnames
mov ax, 4c00h
int 21h
main endp

13. Project 5 clearscreen proc mov ah,06h mov al,00h mov bh,0x9fh
mov cx,0000h
mov dx,184fh
int 10h
ret
clearscreen endp

14. Project 5 getnames proc mov ah,02h mov bh,00 mov dx,0000h int 10h
;display the input string
mov ah,09
lea dx,output1
int 21h
;put the cursor in the top left area
mov dx,0100h

15. Project 5 ;keyboard input mov ah,0ah lea dx,para_list int 21h
;put the cursor just up and left of the screen
mov ah,02h
mov bh,00
mov dx,0200h
int 10h
;display the input string
mov ah,09
lea dx,output2

16. Project 5 ;put the cursor in the top left area mov ah,02h mov bh,00
mov dx,0300h
int 10h
;keyboard input
mov ah,0ah
lea dx,para_list2
int 21h
ret
getnames endp

17. Project 5 compnames proc mov cx,50 lea si,input lea di,input2
repe cmpsb
jg gt
call adddollar

18. Project 5 mov ah,02h mov bh,00 mov dx,0b20h int 10h
;display the input string
mov ah,09
lea dx,input
int 21h
mov dx,0c20h
;display the input2 string
lea dx,input2
ret

19. Project 5 gt: call adddollar mov ah,02h mov bh,00 mov dx,0b20h Int 10h
;display the input2 string
mov ah,09
lea dx,input2
int 21h
mov dx,0c20h
int 10h
;display the input string
lea dx,input
ret
compnames endp

20. Project 5 adddollar proc ;add $ to input
mov al,act_len ;put the length in al
mov ah, ;put ah to 0: ax now contains act_len
mov si,ax ;si now contains act_len
mov input[si],"$" ;add a '$' to the first name
mov al,act_len ;ax contains the length of the second name
mov si,ax ;now si does
mov input2[si],"$" ;add a '$' to the second name
ret
adddollar endp
end main

21. Sorting a table
Arrange data in a table in a certain order, such as ascending or descending.
Sorting algorithm (bubble sort) for (i=0; i<n-1; i++) {
for (j=0; j<n-1-i; j++) {
if (a[j+1] < a[j]) {
tmp = a[j];
a[j] = a[j+1];
a[j+1] = tmp; }

22. Sorting a table-Code LEN EQU 3 LEN_ELEMENT EQU 5 TABLE DB 6,7,1
ENDADDR DW ?
SWAPPED DB 00

23. Sorting a table - Code MOV AX, SI ADD AX,2 MOV ENDADDR, AX
MOV AX, DATASEG ;
MOV DS, AX ;
MOV ES, AX
LEA SI, TABLE
MOV AX, SI
ADD AX,2
MOV ENDADDR, AX

24. Sorting a table - Code MOV SWAPPED, 00 OUTSIDE: LEA SI, TABLE inside:
MOV DI, SI
INC DI
MOV AX, DI
MOV BX, SI
CMPSB
JBE isTheEnd
CALL EXCHANGE
isTheEnd:
MOV SI, AX
CMP SI, ENDADDR
JB inside
CMP SWAPPED, 00
JNZ outside

25. Sorting a table - code EXCHANGE PROC NEAR DEC DI DEC SI MOV BL,[DI]
MOV BH,[SI]
MOV [DI], BH
MOV [SI], BL
MOV SWAPPED, 01
RET
EXCHANGE ENDP

26. Program break down
These four instructions load the offset of table to SI.
LEA SI, TABLE
MOV AX, SI
ADD AX,2
MOV ENDADDR, AX
ENDADDR = offset of table +LENGTH of the table -1
= offset of table + 2 (in this specific example)

27. (TABLE[0] = 6) < (TABLE[1] = 7)
Program break down
; SWAPPED = 0
MOV SWAPPED, 00
LEA SI, TABLE
inside:
MOV DI, SI
INC DI
MOV AX, DI
MOV BX, SI
CMPSB
JBE isTheEnd
CALL EXCHANGE
;SI contains the offset of the table
SI=0
DI = 1
AX= 1
BX= 0
(TABLE[0] = 6) < (TABLE[1] = 7)
SI = 1
DI = 2
Jump to isTheEND

28. Program break down isTheEnd: MOV SI, AX CMP SI, ENDADDR JB inside
CMP SWAPPED, 00
JNZ outside
SI = AX = 1
(SI = 1) < (ENDADDR = 2)
Jump to Inside

29. (TABLE[1] = 7) > (TABLE[2] = 1)
Program break down
inside:
MOV DI, SI
INC DI
MOV AX, DI
MOV BX, SI
CMPSB
JBE isTheEnd
CALL EXCHANGE
SI = 1
DI = 2
AX = 2
BX = 1
(TABLE[1] = 7) > (TABLE[2] = 1)
SI = 2
DI = 3
CALL EXCHANGE

30. Program break down EXCHANGE PROC NEAR DEC DI DEC SI MOV BL,[DI]
MOV BH,[SI]
MOV [DI], BH
MOV [SI], BL
MOV SWAPPED, 01
RET
EXCHANGE ENDP
DI = DI-1 =3-1=2
SI = SI-1 =2-1=1
BL = Table[2]=1
BH = Table[1] = 7
Table[2] = 7
Table[1] = 1
SWAPPED = 1

31. Program break down isTheEnd: MOV SI, AX CMP SI, ENDADDR JB inside
CMP SWAPPED, 00
JNZ outside
SI =AX = 2
(SI = 2) = ENDADDR
(01 != 00)
Jump to outside

32. Program break down Original array: 6 7 1 First pass: 6 1 7
Similarly, second pass would produce:
1 6 7

33. Lab/Practice 1. Open your browser and open this page:
C:\emu8086\documentation\8086_instruction_set.html
And
C:\emu8086\documentation\8086_and_dos_interrupts.html
2. Open your emu8086 software
3. Cut and paste (or type) the following code (as shown in the next page) and save sort.asm

34. page 60,132
TITLE SortPractice ;
STACK SEGMENT PARA STACK 'Stack'
DW DUP(0)
STACK ENDS ;
DATASEG SEGMENT PARA 'Data'
; Please insert your data declaration here
DATASEG ENDS
CODESEG SEGMENT PARA 'Code'
MAIN PROC FAR
MOV AX, DATASEG
MOV DS, AX
MOV ES, AX
; Please insert your code here
MOV AX,4C00H ;exit procedure
INT 21H
MAIN ENDP
CODESEG ENDS
END MAIN ;End of program

35. Practice 4. Modify your code so that:
a. You declare a table with 3 elements, each element has 5 characters
TABLE DB "CCCCC",
DB "BBBBB",
DB "AAAAA"
b. Reuse the sorting code in previous lecture, change the followings:
- re-compute ENDADDR
- in inside loop, re-compute value of DI so that it points to the next element in the array
- in inside loop, modify the code so that it compares two strings instead of comparing two integers
- in exchange proc: modify the code so that it exchange byte by byte from left to right between DS:[SI] and ES:[DI]
5. Compile and run

36. Lab/Practice 1. Open your browser and open this page:
C:\emu8086\documentation\8086_instruction_set.html
And
C:\emu8086\documentation\8086_and_dos_interrupts.html
2. Open your emu8086 software
3. Cut and paste (or type) the following code (as shown in the next page) and save s.asm

37. page 60,132
TITLE ScanPractice ;
STACK SEGMENT PARA STACK 'Stack'
DW DUP(0)
STACK ENDS ;
DATASEG SEGMENT PARA 'Data'
; Please insert your data declaration here
DATASEG ENDS
CODESEG SEGMENT PARA 'Code'
MAIN PROC FAR
MOV AX, DATASEG
MOV DS, AX
MOV ES, AX
; Please insert your code here
MOV AX,4C00H ;exit procedure
INT 21H
MAIN ENDP
CODESEG ENDS
END MAIN ;End of program

38. Practice
4. Modify your code so that:
- It gets a string from keyboard (use INT 21H, 0A). The string has maximum 25 characters
- Code the instructions to scan this string and replace the first occurrence of a space with asterisk (*).
5. Compile and run

39. Lab/Practice 1. Open your browser and open this page:
C:\emu8086\documentation\8086_instruction_set.html
And
C:\emu8086\documentation\8086_and_dos_interrupts.html
2. Open your emu8086 software
3. Cut and paste (or type) the following code (as shown in the next page) and save reverse.asm

40. page 60,132
TITLE ReversePractice ;
STACK SEGMENT PARA STACK 'Stack'
DW DUP(0)
STACK ENDS ;
DATASEG SEGMENT PARA 'Data'
; Please insert your data declaration here
DATASEG ENDS
CODESEG SEGMENT PARA 'Code'
MAIN PROC FAR
MOV AX, DATASEG
MOV DS, AX
MOV ES, AX
; Please insert your code here
MOV AX,4C00H ;exit procedure
INT 21H
MAIN ENDP
CODESEG ENDS
END MAIN ;End of program

41. Practice 4. Modify your code so that: - Define: NAME1 with string
‘COMPUTER TECH’
- NAME2 with 13 blank space
Use LODSB to access each character in NAME1 from left to right
Use STOSB to store each accessed character into NAME2 from right to left.
(NAME2 will contain reverse string of NAME1)
5. Compile and run