I have difficulty printing a character into 0xB800

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Rosnic

Joined: 14 May 2025
Posts: 2

Rosnic 15 May 2025, 22:05

use16
msg db 'ABCD'

mov ax,0xB800
mov es,ax

mov si,msg
mov al,byte [si]

mov [es:di],al
mov [es:di+1],0x07

15 May 2025, 22:05

Picnic

Joined: 05 May 2007
Posts: 1421
Location: Piraeus, Greece

Picnic 15 May 2025, 23:42

Hi Rosnic,

Compile it with FASM and run it in DOSBox.

Code:


    org 0x100 

    mov ax, 0xB800 
    mov es, ax

    mov di, 0x67C        ; Position on screen (row 10, column 30)

    mov si, string     
    mov bx, colors       ; pointer to the color attributes
    mov cx, 6            ; number of characters

    next_char:
    lodsb                ; load byte from ds:si into al, increment si
    mov ah, [bx]         ; load attribute byte into ah
    stosw                ; store ax at es:di, increment di by 2
    inc bx               ; move to next attribute
    loop next_char       ; repeat for all characters

    ret

    string db 'Rosnic'
    colors db 0x0C, 0x0A, 0x0E, 0x09, 0x0B, 0x0F  ; red, green, yellow, blue, cyan, white

I always have the impression that 16-bit assembly is the most fun. Smile

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15 May 2025, 23:42

macomics

Joined: 26 Jan 2021
Posts: 1158
Location: Russia

macomics 16 May 2025, 06:57

Code:

    org 0x100 

    mov ax, 0xB800 
    mov es, ax

    mov di, 2 * (9 * 80 + 30) ; 0x67C        ; Position on screen (row 10, column 30)

    mov si, string     
    mov bx, colors       ; pointer to the color attributes
    mov cx, 6            ; number of characters

    next_char:
    lodsb                ; load byte from ds:si into al, increment si
    mov ah, [bx]         ; load attribute byte into ah
    stosw                ; store ax at es:di, increment di by 2
    inc bx               ; move to next attribute
    loop next_char       ; repeat for all characters

    mov di, 2 * (10 * 80 + 25)
    mov bx, 2 * (11 * 80 + 10)
    mov si, colored_string

    another_loop:
    mov al, [si]
    mov ah, [si + 2]
    stosw
    lodsw
    mov [es:bx], ax
    add bx, 2
    cmp byte [si], 0
    jnz another_loop

    int 0x20 ; ret

    string db 'Rosnic'
    colors db 0x0C, 0x0A, 0x0E, 0x09, 0x0B, 0x0F  ; red, green, yellow, blue, cyan, white

    colored_string db 'R', 0x0C, 'o', 0x0A, 's', 0x0E, 'n', 0x09, 'i', 0x0B, 'c', 0x0F, 0

Last edited by macomics on 24 May 2025, 20:13; edited 1 time in total

16 May 2025, 06:57

Rosnic

Joined: 14 May 2025
Posts: 2

Rosnic 24 May 2025, 20:09

I'm compiling in pure binary code and using the VirtualBox simulator but it doesn't seem to work.

24 May 2025, 20:09

macomics

Joined: 26 Jan 2021
Posts: 1158
Location: Russia

macomics 24 May 2025, 20:26

I have it working on qemu.

Description:
Filesize:	67.85 KB
Viewed:	285 Time(s)

Description:
Filesize:	65.9 KB
Viewed:	285 Time(s)

Description:
Filesize:	60.48 KB
Viewed:	285 Time(s)

24 May 2025, 20:26

Picnic

Joined: 05 May 2007
Posts: 1421
Location: Piraeus, Greece

Picnic 24 May 2025, 23:16

I successfully ran it on DosBOX and Emu8086 (screenshot).

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24 May 2025, 23:16

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