Problem #1 (Example 10.3)
String read and write
//Solution .MODEL small .STACK 100h .DATA w dw 10,15,30,40,50,60,70,80,90,'$' crlf db 0dh, 0ah, '$' .CODE MAIN PROC mov ax, @data mov ds, ax mov ax, 0 lea si, w start: mov bx, [si] cmp bx, '$' je end_ add ax, bx add si, 2 jmp start end_: exit: mov ah, 4ch int 21h ENDP MAIN end MAIN
Problem #2 (Example 10.4, program listing 10.1)
Array (Each element is 16 bit) reverse procedure
//Solution .MODEL small .STACK 100h .DATA w dw 10,20,30,40,50,60,70,80,90,100 crlf db 0dh, 0ah, '$' .CODE MAIN PROC mov ax, @data mov ds, ax lea si, w mov bx, 10 call reverse end_: exit: mov ah, 4ch int 21h ENDP MAIN reverse proc push ax push bx push cx push dx push si push di mov di, si mov cx, bx dec bx shl bx, 1 add di, bx shr cx, 1 xchgloop: mov ax, [si] xchg ax, [di] mov [si], ax add si, 2 sub di, 2 loop xchgloop pop di pop si pop dx pop cx pop bx pop ax ret reverse endp end MAIN
Problem #3 (Section 10.6,Program listing 10.4)
Two dimensional array usage.
Finding the average of different tests
//Solution .MODEL small .STACK 100h .DATA five dw 5 scores dw 67, 45, 98, 33 dw 70, 56, 87, 44 dw 82, 72, 89, 40 dw 80, 67, 95, 50 dw 78, 76, 92, 60 avg dw 5 dup(0) crlf db 0dh, 0ah, '$' .CODE MAIN PROC mov ax, @data mov ds, ax mov si, 6 repeat: mov cx, 5 xor bx, bx xor ax, ax for: add ax, scores[bx+si] add bx, 8 loop for xor dx, dx div five mov avg[si], ax sub si,2 jnl repeat exit: mov ah, 4ch int 21h ENDP MAIN end MAIN
Problem #4
Basic Xlat usage
//Solution .MODEL small .STACK 100h .DATA hello db 10,11,12,13,14,15,16,17,18,19,20 .CODE MAIN PROC mov ax, @data mov ds, ax lea bx, hello mov al, 5 xlat ; XLAT uses the initial value n stored in al, and fetches the nth element from the array exit: mov ah, 4ch int 21h ENDP MAIN end MAIN
Problem #5 (Section 10.7, Program listing 10.5)
Encoding and decoding mesage using XLAT instruction
//Solution
.MODEL small
.STACK 100h
.DATA
; ABCDEFGHIJKLMNOPQRSTUVWXYZ
codekey db 65 dup(' '), 'XQPOGHZBCADEIJUVFMNKLRSTWY'
db 37 dup(' ')
; ABCDEFGHIJKLMNOPQRSTUVWXYZ
decodekey db 65 dup(' '), 'JHIKLQEFMNTURSDCBVWXOPYAZG'
db 37 dup(' ')
coded db 80 dup('$')
prompt db 'Enter a message: $'
crlf db 0dh, 0ah, '$'
.CODE
MAIN PROC
mov ax, @data
mov ds, ax
MOV Ah, 9
LEA dx, prompt
int 21h
mov ah, 1
lea bx, codekey
lea di, coded
while_:
int 21h
cmp al, 0dh
je endwhile
xlat
mov [di], al
inc di
jmp while_
endwhile:
mov ah, 9
lea dx, crlf
int 21h
lea dx, coded
int 21h
lea dx, crlf
int 21h
mov ah, 2
lea bx, decodekey
lea si, coded
while1:
mov al, [si]
cmp al, '$'
je endwhile1
xlat
mov dl, al
int 21h
inc si
jmp while1
endwhile1:
exit:
mov ah, 4ch
int 21h
ENDP MAIN
end MAIN
Problem #6
Change the code in problem 5 to encode and decode for both small letters and capital letters
//Solution To be done by students
Problem #7
Change the code in problem 5 to encode in such way that a letter is replaced by three letters ahead.
For example A becomes D and B becomes E
//Solution To be done by students