OSDev.org

Posted: **Thu Apr 17, 2025 3:37 am**

Hello everyone. I am new to operating system development.
I have a problem. When I add more functionality to my OS, the text starts disappearing from the screen.
I tried to move programs from 800h to 2000h, but it did not help.
Help me pls!

Code: Select all

[BITS 16]
[ORG 500h]

start:
    cli
    call set_video_mode
    call print_interface
    call print_newline
    call print_newline
    call shell
    jmp $

set_video_mode:
    mov ax, 0x12
    int 0x10
    ret

print_string:
    mov ah, 0x0E
    mov bl, 0x0F
.print_char:
    lodsb
    cmp al, 0
    je .done
    int 0x10
    jmp .print_char
.done:
    ret
    
print_newline:
    mov ah, 0x0E
    mov al, 0x0D
    int 0x10
    mov al, 0x0A
    int 0x10
    ret

print_interface:
    mov si, header
    call print_string
    mov si, info
    call print_string_green
    mov si, menu
    call print_string_green
    ret

print_help:
    mov si, menu
    call print_string_green
    call print_newline
    ret

shell:
    mov si, prompt
    call print_string
    call read_command
    call print_newline
    call execute_command
    jmp shell

; ===================== Shell =====================

read_command:
    mov di, command_buffer
    xor cx, cx
.read_loop:
    mov ah, 0x00
    int 0x16
    cmp al, 0x0D
    je .done_read
    cmp al, 0x08
    je .handle_backspace
    cmp cx, 255
    jge .done_read
    stosb
    mov ah, 0x0E
    mov bl, 0x1F
    int 0x10
    inc cx
    jmp .read_loop

.handle_backspace:
    cmp di, command_buffer
    je .read_loop
    dec di
    dec cx
    mov ah, 0x0E
    mov al, 0x08
    int 0x10
    mov al, ' '
    int 0x10
    mov al, 0x08
    int 0x10
    jmp .read_loop

.done_read:
    mov byte [di], 0
    ret

execute_command:
    mov si, command_buffer
    ; Проверка команды "help"
    mov di, help_str
    call compare_strings
    je do_help
    
    mov si, command_buffer
    ; Проверка команды "info"
    mov di, info_str
    call compare_strings
    je print_OS_info

    mov si, command_buffer
    ; Проверка команды "cls"
    mov di, cls_str
    call compare_strings
    je do_cls
    
    mov si, command_buffer
    ; Проверка команды "CPU"
    mov di, CPU_str
    call compare_strings
    je do_CPUinfo
    
    mov si, command_buffer
    ; Проверка команды "date"
    mov di, date_str
    call compare_strings
    je print_date
    
    mov si, command_buffer
    ; Проверка команды "time"
    mov di, time_str
    call compare_strings
    je print_time

    mov si, command_buffer
    ; Проверка команды "shut"
    mov di, shut_str
    call compare_strings
    je do_shutdown
    
    mov si, command_buffer
    ; Проверка команды "reboot"
    mov di, reboot_str
    call compare_strings
    je do_reboot
   
    mov si, command_buffer
    ; Проверка команды "writer"
    mov di, writer_str
    call compare_strings
    je start_writer
    
    mov si, command_buffer
    ; Проверка команды "brainf"
    mov di, brainf_str
    call compare_strings
    je start_brainf
    
    mov si, command_buffer
    ; Проверка команды "barchart"
    mov di, barchart_str
    call compare_strings
    je start_barchart
    
    mov si, command_buffer
    ; Проверка команды "snake"
    mov di, snake_str
    call compare_strings
    je start_snake
    
    mov si, command_buffer
    ; Проверка команды "calc"
    mov di, calc_str
    call compare_strings
    je start_calc
    
    mov si, command_buffer
    ; Проверка команды "disk-tools"
    mov di, disk_tools_str
    call compare_strings
    je start_disk_tools
    
    mov si, command_buffer
    ; Проверка команды "BASIC"
    mov di, BASIC_str
    call compare_strings
    je start_BASIC
    
    mov si, command_buffer
    ; Проверка команды "load"
    mov di, load_str
    call compare_strings
    je load_program

    call unknown_command
    ret

compare_strings:
    xor cx, cx
.next_char:
    lodsb
    cmp al, [di]
    jne .not_equal
    cmp al, 0
    je .equal
    inc di
    jmp .next_char
.not_equal:
    ret
.equal:
    ret

help_str db 'help', 0
info_str db 'info', 0
cls_str db 'cls', 0
shut_str db 'shut', 0
reboot_str db 'reboot', 0
CPU_str db 'CPU', 0
date_str db 'date', 0
time_str db 'time', 0
load_str db 'load', 0
writer_str db 'writer', 0
brainf_str db 'brainf', 0
barchart_str db 'barchart', 0
snake_str db 'snake', 0
calc_str db 'calc', 0
disk_tools_str db 'disk-tools', 0
BASIC_str db 'BASIC', 0

; ===================== Other =====================
do_banner:
    call print_interface
    call print_newline
    ret

do_help:
    call print_newline
    call print_help
    call print_newline
    ret

do_cls:
    pusha
    mov ax, 0x12
    int 0x10
    popa
    ret

unknown_command:
    mov si, unknown_msg
    call print_string_red
    call print_newline
    ret

do_shutdown:
    mov ax, 0x5307
    mov bx, 0x0001
    mov cx, 0x0003
    int 0x15
    ret
    
do_reboot:
    int 0x19
    ret
    
print_OS_info:
    mov si, info
    call print_string_green
    call print_newline
    ret
       
;===================== Start programs =====================

start_writer:
    pusha
    mov ah, 0x02
    mov al, 2       ; Количество секторов для чтения
    mov ch, 0       ; Номер дорожки
    mov dh, 0       ; Номер головки
    mov cl, 9       ; Номер сектора
    mov bx, 800h    ; Адрес загрузки
    int 0x13
    jc .disk_error  ; Если ошибка, перейти к обработке
    jmp 800h        ; Переход к загруженной программе
.disk_error:
    mov si, disk_error_msg
    call print_string_red
    call print_newline
    popa
    ret
    
start_brainf:
    pusha
    mov ah, 0x02
    mov al, 2       ; Количество секторов для чтения
    mov ch, 0       ; Номер дорожки
    mov dh, 0       ; Номер головки
    mov cl, 12       ; Номер сектора
    mov bx, 800h    ; Адрес загрузки
    int 0x13
    jc .disk_error  ; Если ошибка, перейти к обработке
    jmp 800h        ; Переход к загруженной программе
.disk_error:
    mov si, disk_error_msg
    call print_string_red
    call print_newline
    popa
    ret
   
start_barchart:
    pusha
    mov ah, 0x02
    mov al, 1       ; Количество секторов для чтения
    mov ch, 0       ; Номер дорожки
    mov dh, 0       ; Номер головки
    mov cl, 15      ; Номер сектора
    mov bx, 800h    ; Адрес загрузки
    int 0x13
    jc .disk_error  ; Если ошибка, перейти к обработке
    jmp 800h        ; Переход к загруженной программе
.disk_error:
    mov si, disk_error_msg
    call print_string_red
    call print_newline
    popa
    ret
    
start_snake:
    pusha
    mov ah, 0x02
    mov al, 2       ; Количество секторов для чтения
    mov ch, 0       ; Номер дорожки
    mov dh, 0       ; Номер головки
    mov cl, 16      ; Номер сектора
    mov bx, 800h    ; Адрес загрузки
    int 0x13
    jc .disk_error  ; Если ошибка, перейти к обработке
    jmp 800h        ; Переход к загруженной программе
.disk_error:
    mov si, disk_error_msg
    call print_string_red
    call print_newline
    popa
    ret
    
start_calc:
    pusha
    mov ah, 0x02
    mov al, 2       ; Количество секторов для чтения
    mov ch, 0       ; Номер дорожки
    mov dh, 0       ; Номер головки
    mov cl, 18      ; Номер сектора
    mov bx, 800h    ; Адрес загрузки
    int 0x13
    jc .disk_error  ; Если ошибка, перейти к обработке
    jmp 800h        ; Переход к загруженной программе
.disk_error:
    mov si, disk_error_msg
    call print_string_red
    call print_newline
    popa
    ret
    
start_disk_tools:
    push bx
    mov ah, 0x02
    mov al, 4       ; Количество секторов для чтения
    mov ch, 0       ; Номер дорожки
    mov dh, 0       ; Номер головки
    mov cl, 20      ; Номер сектора
    mov bx, 800h    ; Адрес загрузки
    int 0x13
    jc .disk_error  ; Если ошибка, перейти к обработке
    jmp 800h        ; Переход к загруженной программе
.disk_error:
    mov si, disk_error_msg
    call print_string_red
    call print_newline
    pop bx
    ret
    
start_BASIC:
    mov ax, 0x02
    int 0x10
    pusha
    mov ah, 0x02
    mov al, 9       ; Количество секторов для чтения
    mov ch, 0       ; Номер дорожки
    mov dh, 0       ; Номер головки
    mov cl, 25      ; Номер сектора
    mov bx, 800h    ; Адрес загрузки
    int 0x13
    jc .disk_error  ; Если ошибка, перейти к обработке
    jmp 800h        ; Переход к загруженной программе
.disk_error:
    mov si, disk_error_msg
    call print_string_red
    call print_newline
    popa
    ret

; ===================== CPU info functions ===================== 
print_edx:
    mov ah, 0eh

    mov bx, 4
    loop4r:
        mov al, dl
        int 10h
        ror edx, 8

        dec bx
        cmp bx, 0
        jne loop4r
    ret
    
print_full_name_part:
    cpuid
    push edx
    push ecx
    push ebx
    push eax

    mov cx, 4
loop4n:
    pop edx
    call print_edx

    dec cx
    cmp cx, 0
    jne loop4n

    ret

print_cores:
    mov si, cores
    call print_string
    mov eax, 1
    cpuid
    ror ebx, 16
    mov al, bl
    call print_al
    ret

print_cache_line:
    mov si, cache_line
    call print_string
    mov eax, 1
    cpuid
    ror ebx, 8
    mov al, bl
    mov bl, 8
    mul bl
    call print_al
    ret

print_stepping:
    mov si, stepping
    call print_string
    mov eax, 1
    cpuid
    and al, 15
    call print_al
    ret
 
print_al:
    mov ah, 0
    mov dl, 10
    div dl
    add ax, '00'
    mov dx, ax

    mov ah, 0eh
    mov al, dl
    cmp dl, '0'
    jz skip_fn
    mov bl, 0x0F
    int 10h
skip_fn:
    mov al, dh
    mov bl, 0x0F
    int 10h
    ret
    
do_CPUinfo:
    push eax
    mov si, cpu_name
    call print_string
    ; Выводим информацию о ЦПУ
    mov eax, 80000002h
    call print_full_name_part
    mov eax, 80000003h
    call print_full_name_part
    mov eax, 80000004h
    call print_full_name_part
    mov si, mt
    call print_string
    call print_cores
    mov si, mt
    call print_string
    call print_cache_line
    mov si, mt
    call print_string
    call print_stepping
    mov si, mt
    call print_string
    pop eax
    ret
    
cpu_name db '  CPU name: ', 0
cores db '  CPU cores: ', 0
stepping db '  Stepping ID: ', 0
cache_line db '  Cache line: ', 0

; ===================== About OS =====================

info db 10, 13
     db '+--------------------------------------------+', 10, 13
     db '|  x16 PRos is the simple 16 bit operating   |', 10, 13
     db '|  system written in NASM for x86 PC`s       |', 10, 13
     db '|--------------------------------------------|', 10, 13
     db '|  Autor: PRoX (https://github.com/PRoX2011) |', 10, 13
     db '|  Amount of disk sectors: 25                |', 10, 13
     db '|  OS version: 0.2.6                         |', 10, 13
     db '+============================================+', 10, 13, 0

; ===================== Date and time functions =====================

; Функция для вывода даты
; Выводит дату в формате DD.MM.YY
print_date:
    mov si, date_msg
    call print_string
    
    pusha
    ; Получить дату
    mov ah, 0x04
    int 0x1a  ; Получаем дату: ch - век, cl - год, dh - месяц, dl - день

    mov ah, 0x0e  ; Установить функцию для вывода символа

    ; Вывести день (dl)
    mov al, dl
    shr al, 4
    add al, '0'  ; Преобразовать в ASCII
    mov bl, 0x0B
    int 0x10     ; Выводим
    mov al, dl
    and al, 0x0F
    add al, '0'  ; Преобразовать в ASCII
    int 0x10     ; Выводим

    ; Вывести точку
    mov al, '.'
    mov bl, 0x0B
    int 0x10

    ; Вывести месяц (dh)
    mov al, dh
    shr al, 4
    add al, '0'
    mov bl, 0x0B
    int 0x10
    mov al, dh
    and al, 0x0F
    add al, '0'
    mov bl, 0x0B
    int 0x10

    ; Вывести точку
    mov al, '.'
    mov bl, 0x0B
    int 0x10

    ; Вывести год (cl)
    mov al, cl
    shr al, 4
    add al, '0'
    mov bl, 0x0B
    int 0x10
    mov al, cl
    and al, 0x0F
    add al, '0'
    mov bl, 0x0B
    int 0x10
    
    mov si, mt
    call print_string
    
    popa
    ret
    
date_msg db 'Current date: ', 0

; Функция для вывода времяни
; Выводит дату в формате HH.MM.SS
print_time:
    mov si, time_msg
    call print_string
    
    pusha
    ; Получить время
    mov ah, 0x02
    int 0x1a  ; Получаем время: ch - часы, cl - минуты, dh - секунды

    mov ah, 0x0e  ; Установить функцию для вывода символа

    ; Вывести часы
    mov al, ch
    shr al, 4
    add al, '0'  ; Преобразовать в ASCII
    mov bl, 0x0B
    int 0x10     ; Выводим
    mov al, ch
    and al, 0x0F
    add al, '0'  ; Преобразовать в ASCII
    mov bl, 0x0B
    int 0x10     ; Выводим

    ; Вывести разделитель
    mov al, ':'
    mov bl, 0x0B
    int 0x10

    ; Вывести минуты
    mov al, cl
    shr al, 4
    add al, '0'
    mov bl, 0x0B
    int 0x10
    mov al, cl
    and al, 0x0F
    add al, '0'
    mov bl, 0x0B
    int 0x10

    ; Вывести разделитель
    mov al, ':'
    mov bl, 0x0B
    int 0x10

    ; Вывести секунды
    mov al, dh
    shr al, 4
    add al, '0'
    mov bl, 0x0B
    int 0x10
    mov al, dh
    and al, 0x0F
    add al, '0'
    mov bl, 0x0B
    int 0x10
    
    mov si, mt
    call print_string
    
    popa
    ret
    
time_msg db 'Current time: ', 0

; ===================== Load Command =====================

load_program:
    mov si, load_prompt
    call print_string
    call read_number  
    call print_newline

    call start_program
    ret

read_number:
    mov di, number_buffer
    xor cx, cx
.read_loop:
    mov ah, 0x00
    int 0x16
    cmp al, 0x0D    
    je .done_read
    cmp al, 0x08     
    je .handle_backspace
    cmp cx, 5       
    jge .read_loop 
    cmp al, '0'       
    jb .read_loop
    cmp al, '9'
    ja .read_loop
    stosb      
    mov ah, 0x0E     
    mov bl, 0x1F
    int 0x10
    inc cx            
    jmp .read_loop

.handle_backspace:
    cmp cx, 0       
    je .read_loop
    dec di           
    dec cx            
    mov ah, 0x0E      
    mov al, 0x08     
    int 0x10
    mov al, ' '     
    int 0x10
    mov al, 0x08  
    int 0x10
    jmp .read_loop

.done_read:
    mov byte [di], 0  
    call convert_to_number  
    ret

convert_to_number:
    mov si, number_buffer
    xor ax, ax
    xor cx, cx
.convert_loop:
    lodsb
    cmp al, 0    
    je .done_convert
    sub al, '0'    
    imul cx, 10       
    add cx, ax      
    jmp .convert_loop
.done_convert:
    mov [sector_number], cx  
    ret

start_program:
    pusha
    mov ah, 0x02     
    mov al, 1       
    mov ch, 0       
    mov dh, 0     
    mov cl, [sector_number] 
    mov bx, 800h   
    int 0x13
    jc .disk_error  
    jmp 800h
    ret

.disk_error:
    mov si, disk_error_msg
    call print_string_red
    popa
    ret

load_prompt db 'Enter sector number: ', 0
disk_error_msg db 'Disk read error!', 0
number_buffer db 6 dup(0)
sector_number dw 0

; ===================== print =====================

; Зелёное на чёрном
print_string_green:
    mov ah, 0x0E
    mov bl, 0x0A
.print_char:
    lodsb
    cmp al, 0
    je .done
    int 0x10
    jmp .print_char
.done:
    ret
    
print_string_cyan:
    mov ah, 0x0E
    mov bl, 0x0B
.print_char:
    lodsb
    cmp al, 0
    je .done
    int 0x10
    jmp .print_char
.done:
    ret
    
print_string_red:
    mov ah, 0x0E
    mov bl, 0x0C
.print_char:
    lodsb
    cmp al, 0
    je .done
    int 0x10
    jmp .print_char
.done:
    ret
    
; ===================== Data section =====================

header db '============================= x16 PRos v0.2 ====================================', 0
menu db '+--------------------------------------------+', 10, 13
     db '|Commands:                                   |', 10, 13
     db '|  help - get list of the commands           |', 10, 13
     db '|  info - print information about OS         |', 10, 13
     db '|  cls - clear terminal                      |', 10, 13
     db '|  shut - shutdown PC                        |', 10, 13
     db '|  reboot - go to bootloader (restart system)|', 10, 13
     db '|  date - print current date (DD.MM.YY)      |', 10, 13
     db '|  time - print current time (HH.MM.SS)      |', 10, 13
     db '|  CPU - print CPU info                      |', 10, 13
     db '|  load - load program from disk sector      |', 10, 13
     db '|  writer - text editor                      |', 10, 13
     db '|  brainf - brainf IDE                       |', 10, 13
     db '|  barchart - charting soft (by Loxsete)     |', 10, 13
     db '|  snake - snake game                        |', 10, 13
     db '|  calc - calculator program (by Saeta)      |', 10, 13
     db '|  disk-tools - disk utility (disk 0x80)     |', 10, 13
     db '|  BASIC - start micro-BASIC interpriter     |', 10, 13
     db '+============================================+', 0
unknown_msg db 'Unknown command.', 0
prompt db '[PRos] > ', 0
mt db '', 10, 13, 0
buffer db 512 dup(0)
command_buffer db 128 dup(0)

Full OS code: https://github.com/PRoX2011/x16-PRos

Posted: **Thu Apr 17, 2025 1:30 pm**

What do you use as bootloader? Cause I don't see you setting up segments and stack.

Posted: **Thu Apr 17, 2025 1:38 pm**

Here is my bootloader code:

Code: Select all

[BITS 16]
[ORG 7C00h]

start:
    cli
    xor ax, ax
    mov ds, ax
    mov es, ax

    ; Установка видеорежима
    call set_video_mode

    ; Очистка экрана
    mov bl, 0x01
    mov cx, 2000
    mov di, 0xB800
    rep stosw
    

    mov si, baner
    call print_string
    
    mov si, check_msg
    call print_string
    
    ; Проверка диска
    call check_disk
    jc disk_error

    ; Проверка RAM
    call check_ram
    jc ram_error

    ; Проверка CPU
    call check_cpu
    jc cpu_error

    ; Все проверки пройдены успешно
    mov si, ready_message
    call print_string_green
    
    mov si, wait_msg
    call print_string
    
    ; Ожидание нажатия любой клавиши
    call wait_for_key

    ; Переход к ядру ОС
    jmp 500h

disk_error:
    mov si, disk_error_message
    call print_string
    jmp $

ram_error:
    mov si, ram_error_message
    call print_string
    jmp $

cpu_error:
    mov si, cpu_error_message
    call print_string
    jmp $

set_video_mode:
    mov ax, 0x12
    int 0x10
    ret

print_string:
    mov ah, 0x0E
    mov bh, 0x00
    mov bl, 0x1F
.print_char:
    lodsb
    cmp al, 0
    je .done
    int 0x10
    jmp .print_char
.done:
    ret
    
print_string_green:
    mov ah, 0x0E
    mov bh, 0x00
    mov bl, 0x0A
.print_char:
    lodsb
    cmp al, 0
    je .done
    int 0x10
    jmp .print_char
.done:
    ret

wait_for_key:
    mov ah, 0x00
    int 0x16
    ret

check_disk:
    mov ah, 0x02
    mov al, 6        
    mov ch, 0         
    mov dh, 0        
    mov cl, 2       
    mov bx, 500h     
    int 0x13         
    ret

check_ram:
    ; Простая проверка RAM (можно расширить)
    mov ax, 0x0000
    mov es, ax
    mov di, 0x1000
    mov cx, 0x1000
    rep stosw
    ret

check_cpu:
    ; Простая проверка CPU (можно расширить)
    ; Например, проверка наличия 386+ инструкций
    pushf
    pop ax
    and ax, 0x0FFF
    push ax
    popf
    pushf
    pop ax
    and ax, 0xF000
    cmp ax, 0xF000
    je .cpu_error
    clc
    ret
.cpu_error:
    stc
    ret

baner db "     /_ | / / |  __ \|  __ \", 13, 10,
      db " __  _| |/ /_ | |__) | |__) |___  ___ ", 13, 10,
      db " \ \/ / | '_ \|  ___/|  _  // _ \/ __|", 13, 10,
      db "  >  <| | (_) | |    | | \ \ (_) \__ \", 13, 10,
      db " /_/\_\_|\___/|_|    |_|  \_\___/|___/", 13, 10, 13, 10, 0
disk_error_message db "Disk [ERROR]", 13, 10, 0
ram_error_message db "RAM [ERROR]", 13, 10, 0
cpu_error_message db "CPU [ERROR]", 13, 10, 0
ready_message db "Disk [OK]", 13, 10, 
              db "RAM  [OK]", 13, 10, 
              db "CPU  [OK]", 13, 10, 13, 10, 0
wait_msg db "Press any key to boot...", 0
check_msg db "Checking components:", 13, 10, 13, 10, 0
times 510 - ($ - $$) db 0
dw 0xAA55

My bootloader loads the kernel into memory at the address 500h, and then moves on to it through Jmp
If it is possible, could you briefly tell me about my problem and what is it?

Posted: **Thu Apr 17, 2025 2:03 pm**

You are loading a hardcoded amount of 6 sectors to 0x500. This is enough for 3072 bytes. How big is your kernel image when the problem starts to happen? You also never set CS to 0, but this is unlikely to be your problem in this day and age.

Posted: **Fri Apr 18, 2025 7:04 am**

You also disable hardware interrupts in your bootloader. I don't know, but maybe some BIOSes rely on them for disk access?
You also don't setup a stack before using it.

Code: Select all

 
    xor ax, ax
    (...)
    ; Очистка экрана
    mov bl, 0x01
    mov cx, 2000
    mov di, 0xB800
    rep stosw

What do you think you are doing here? I assume you want to clear video mem at 0xB8000. But you write to 0xB800 instead.
And additionally everything nullplan has written.

Posted: **Fri Apr 18, 2025 2:21 pm**

sebihepp wrote: ↑Fri Apr 18, 2025 7:04 am You also disable hardware interrupts in your bootloader. I don't know, but maybe some BIOSes rely on them for disk access?

That cannot possibly be a problem, because a real mode interrupt transfer always disables the interrupt flag. Any BIOS interrupt function requiring interrupts to work always has to re-enable the interrupt flag itself, irrespective of the setting in the main program.

The remainder of your post, yes, those are also problems.

Posted: **Sat Apr 19, 2025 8:45 am**

nullplan wrote: ↑Fri Apr 18, 2025 2:21 pm That cannot possibly be a problem, because a real mode interrupt transfer always disables the interrupt flag. Any BIOS interrupt function requiring interrupts to work always has to re-enable the interrupt flag itself, irrespective of the setting in the main program.

I am sorry. I forgot that RM interrupts clear the int flag.

OSDev.org

OS Text Disappearance

OS Text Disappearance

Re: OS Text Disappearance

Re: OS Text Disappearance

Re: OS Text Disappearance

Re: OS Text Disappearance

Re: OS Text Disappearance

Re: OS Text Disappearance