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>On 2002-03-15 16:13:47, Sum Dude wrote:
>Has anyone got a peice of code (in nasm) that (using lodsb and no stack or anything like that) reads a byte and displays it?
i got it! if you mean to display the byte as it is...
>(dont want to use any int21 stuff)
you copy the string, whatever you want to print pointed with si, with lodsb to al and then put 0x07 (for normal format) in ah, and then mov [es:di],ax for es:di=>0xb800:(offset within 1 page on the screen) or es:di=>0xb000:(offset) if you have monochrome CRT. Do place the string, set conditions such as or al,al, then jz .done, like a while(...){} loop.
You can view a copy of my bootsector (that's where i'm testing my I/O functions w/o even BIOS), I've messed it up completely (but have some good functions written), so I'm writing a new one starting from scratch again thus I have no copies of it on the internet...but here is a sneak peak:
;; sprintf(char *string, int offset)
;; usage:
;; -----
;; mov byte ax,0 ; some kind of offset
;; push ax
;; move byte ax,string1 ;pointer to string
;; push ax
;; call sprintf ; call the f(x)
;; -----
;; this one is a near call, so takes argument from
;; bp+4 as first one
;; if you plan on to use a far call the arguments
;; are loaded as bp+6
sprintf:
push bp ; saves bp
mov bp,sp ; prepares bp for arguments
pusha ; prepare stack
mov di,0xb800 ; move in the video ram
mov es,di ; set es
mov di,[bp+6] ; set di to destinated offset
mov byte si,[bp+4] ; load string to print
.begin: ; while (pre-condition) {
mov ah,0x0f ; set attribute
lodsb ; load 1 byte from string
cmp al,0x00 ; if (al == 0x00)
jz .done ; true: done
mov word [es:di],ax ; otherwise override into mem
add di,2 ; add to bytes to video counter
jmp .begin ; } // loop back
.done:
mov bp+6,di
popa
leave
ret
That's it...
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