Reputation: 33
x86 Strange printing after console has been scrolled
I have the following function:
printRows proc
mov cx, 25
printRowsLoop:
mov si, 0
printSingleRowLoop:
mov ah, 3 ;save current cursor position at dx (dh:dl)
int 10h
push dx ;keep the position for later
mov ah, 2
mov dl, '&'
int 21h ; print '&' char in the current curser position
pop dx ; restore dx
add dl, 5 ; increase the column of it with a const number (so it would look like a square)
mov ah, 2
int 10h
inc si
cmp si, 3 ; print 3 '&' in each row
jne printSingleRowLoop
mov dl, 13 ; result of these 3 groups of commands should be 2 new lines
mov ah, 2
int 21h
mov dl, 10
;mov ah, 2 ; ah is alredy 2
int 21h
;mov dl, 10 ; dl is already 10
;mov ah,2 ; ah is already 2
int 21h
loop printRowsLoop ; print (cx) lines
ret
printRows endp
the output of it should be what is seen in the this screenshot - and this is the output of it (at least in the begginig)
but, after the "good" output filled the console (when it needed to "scroll") it doesn't longer print those spaces between each '&', instead it just prints each of them in a new line as can be seen here.
What might cause such strange behaviour? What am I doing wrong? How should I fix this?
I am using emu8086.
Upvotes: 3
Views: 111
Answers (3)
Reputation: 400
You should print the carriage return (13 ascii code) last.
I have also included Fifoernik's tips in my answer.
printRows proc
mov cx, 25
printRowsLoop:
mov si, 0
printSingleRowLoop:
push cx
mov bh, 0
mov ah, 3 ;save current cursor position at dx (dh:dl)
int 10h
pop cx
push dx ;keep the position for later
mov ah, 2
mov dl, '&'
int 21h ; print '&' char in the current curser position
pop dx ; restore dx
mov bh, 0
add dl, 5 ; increase the column of it with a const number (so it would look like a square)
mov ah, 2
int 10h
inc si
cmp si, 3 ; print 3 '&' in each row
jne printSingleRowLoop
mov dl, 10
;mov ah, 2 ; ah is alredy 2
int 21h
;mov dl, 10 ; dl is already 10
;mov ah,2 ; ah is already 2
int 21h
mov dl, 13 ; <<<<<<<<<<<<<<<<<<<<< print the carriage return last!
;mov ah, 2 ; ah is already 2
int 21h
loop printRowsLoop ; print (cx) lines
ret
printRows endp
No need for an extra space character:)
Upvotes: 4
Reputation: 10371
The problem is the way you are inserting the line breaks. What you do is to display char 13, 10, 10. The solution is to display a blank space after the line breaks (13, 10, 10, ' ') :
mov dl, ' '
mov ah, 2
int 21h
To align the first line, we will have to display another space at the beginning:
printRows proc
mov ah, 2 ;<=============================================
mov dl, ' ' ;<=============================================
int 21h ;<=============================================
mov cx, 25
printRowsLoop:
mov si, 0
printSingleRowLoop:
mov ah, 3 ;save current cursor position at dx (dh:dl)
int 10h
push dx ;keep the position for later
mov ah, 2
mov dl, '&'
int 21h ; print '&' char in the current curser position
pop dx ; restore dx
add dl, 5 ; increase the column of it with a const number (so it would look like a square)
mov ah, 2
int 10h
inc si
cmp si, 3 ; print 3 '&' in each row
jne printSingleRowLoop
mov dl, 13 ; result of these 3 groups of commands should be 2 new lines
mov ah, 2
int 21h
mov dl, 10
;mov ah, 2 ; ah is alredy 2
int 21h
;mov dl, 10 ; dl is already 10
;mov ah,2 ; ah is already 2
int 21h
mov dl, ' ' ;<=============================================
mov ah, 2 ;<=============================================
int 21h ;<=============================================
loop printRowsLoop ; print (cx) lines
ret
printRows endp
Upvotes: 0
Reputation: 9899
Your code has some problems:
The BIOS cursor functions require the BH argument to be specified. It represents the display page. Best set it at zero.
The BIOS GetCursor call will destroy the CX register that you need for your loop control. You don't actually need the values returned in CX so just PUSH/POP it.
Use this:
...
push cx
mov bh, 0 ;display page 0
mov ah, 3 ;save current cursor position at dx (dh:dl)
int 10h ;GetCursor
pop cx
...
mov bh, 0 ;display page 0
mov ah, 2
int 10h ;SetCursor
...
Normally these corrections would not solve the issue of scrolling but emu8086 is a program with a lot of problems. You might get lucky!
Upvotes: 2