[bits 16] ; tell assembler that working in real mode(16 bit mode)
[org 0x7c00] ; organize from 0x7C00 memory location where BIOS will load us
start: ; start label from where our code starts
xor ax,ax ; set ax register to 0
mov ds,ax ; set data segment(ds) to 0
mov es,ax ; set extra segment(es) to 0
mov bx,0x8000
mov ax,0x13 ;clears the screen
int 0x10 ;call bios video interrupt
mov ah,02 ;clear the screen with big font
int 0x10 ;interrupt display
;set cursor to specific position on screen
mov ah,0x02 ; set value for change to cursor position
mov bh,0x00 ; page
mov dh,0x06 ; y cordinate/row
mov dl,0x09 ; x cordinate/col
int 0x10
mov si, start_os_intro ; point start_os_intro string to source index
call _print_DiffColor_String ; call print different color string function
;set cursor to specific position on screen
mov ah,0x02
mov bh,0x00
mov dh,0x10
mov dl,0x06
int 0x10
mov si,press_key ; point press_key string to source index
call _print_GreenColor_String ; call print green color string function
mov ax,0x00 ; get keyboard input
int 0x16 ; interrupt for hold & read input
;/////////////////////////////////////////////////////////////
; load second sector into memory
mov ah, 0x02 ; load second stage to memory
mov al, 1 ; numbers of sectors to read into memory
mov dl, 0x80 ; sector read from fixed/usb disk
mov ch, 0 ; cylinder number
mov dh, 0 ; head number
mov cl, 2 ; sector number
mov bx, _OS_Stage_2 ; load into es:bx segment :offset of buffer
int 0x13 ; disk I/O interrupt
jmp _OS_Stage_2 ; jump to second stage
;/////////////////////////////////////////////////////////////
; declaring string datas here
start_os_intro db ' Welcome to MarsOS!',0
press_key db '>>>> Press any key to start <<<<',0
login_username db 'Username : ',0
login_password db 'Password : ',0
display_text db ' ##Welcome to MarsOS##', 0
os_info db 10, 'OS: MarsOS Bits: 16-Bit ver: version=1.0',13,0
press_key_2 db 10,'Press any key to go to gui view...',0
window_text db 10,'GUI', 0
hello_world_text db 10,10, ' Hello World!',0
login_label db '#] Login....(ESC to skip login)', 0
;/////////////////////////////////////////////////////////////
; defining printing string functions here
;****** print string without color
print_string:
mov ah, 0x0E ; value to tell interrupt handler that take value from al & print it
.repeat_next_char:
lodsb ; get character from string
cmp al, 0 ; cmp al with end of string
je .done_print ; if char is zero, end of string
int 0x10 ; otherwise, print it
jmp .repeat_next_char ; jmp to .repeat_next_char if not 0
.done_print:
ret ;return
;****** print string with different colors
_print_DiffColor_String:
mov bl,1 ;color value
mov ah, 0x0E
.repeat_next_char:
lodsb
cmp al, 0
je .done_print
add bl,6 ;increase color value by 6
int 0x10
jmp .repeat_next_char
.done_print:
ret
;****** print string with green color
_print_GreenColor_String:
mov bl,10
mov ah, 0x0E
.repeat_next_char:
lodsb
cmp al, 0
je .done_print
int 0x10
jmp .repeat_next_char
.done_print:
ret
;****** print string with white color
_print_WhiteColor_String:
mov bl,15
mov ah, 0x0E
.repeat_next_char:
lodsb
cmp al, 0
je .done_print
int 0x10
jmp .repeat_next_char
.done_print:
ret
;****** print string with yellow color
_print_YellowColor_String:
mov bl,14
mov ah, 0x0E
.repeat_next_char:
lodsb
cmp al, 0
je .done_print
int 0x10
jmp .repeat_next_char
.done_print:
ret
;///////////////////////////////////////////
; boot loader magic number
times ((0x200 - 2) - ($ - $$)) db 0x00 ;set 512 bytes for boot sector which are necessary
dw 0xAA55 ; boot signature 0xAA & 0x55
;////////////////////////////////////////////////////////////////////////////////////////
_OS_Stage_2 :
mov al,2 ; set font to normal mode
mov ah,0 ; clear the screen
int 0x10 ; call video interrupt
mov cx,0 ; initialize counter(cx) to get input
;***** print login_label on screen
;set cursor to specific position on screen
mov ah,0x02
mov bh,0x00
mov dh,0x00
mov dl,0x00
int 0x10
mov si,login_label ; point si to login_username
call print_string ; display it on screen
;****** read username
;set cursor to specific position on screen
mov ah,0x02
mov bh,0x00
mov dh,0x02
mov dl,0x00
int 0x10
mov si,login_username ; point si to login_username
call print_string ; display it on screen
_getUsernameinput:
mov ax,0x00 ; get keyboard input
int 0x16 ; hold for input
cmp ah,0x1C ; compare input is enter(1C) or not
je .exitinput ; if enter then jump to exitinput
cmp ah,0x01 ; compare input is escape(01) or not
je _skipLogin ; jump to _skipLogin
mov ah,0x0E ;display input char
int 0x10
inc cx ; increase counter
cmp cx,5 ; compare counter reached to 5
jbe _getUsernameinput ; yes jump to _getUsernameinput
jmp .inputdone ; else jump to inputdone
.inputdone:
mov cx,0 ; set counter to 0
jmp _getUsernameinput ; jump to _getUsernameinput
ret ; return
.exitinput:
hlt
;****** read password
;set x y position to text
mov ah,0x02
mov bh,0x00
mov dh,0x03
mov dl,0x00
int 0x10
mov si,login_password ; point si to login_username
call print_string ; display it on screen
_getPasswordinput:
mov ax,0x00
int 0x16
cmp ah,0x1C
je .exitinput
cmp ah,0x01
je _skipLogin
inc cx
cmp cx,5
jbe _getPasswordinput
jmp .inputdone
.inputdone:
mov cx,0
jmp _getPasswordinput
ret
.exitinput:
hlt
;****** display display_text on screen
;set x y position to text
mov ah,0x02
mov bh,0x00
mov dh,0x08
mov dl,0x12
int 0x10
mov si, display_text ;display display_text on screen
call print_string
;set x y position to text
mov ah,0x02
mov bh,0x00
mov dh,0x9
mov dl,0x10
int 0x10
mov si, os_info ;display os_info on screen
call print_string
;set x y position to text
mov ah,0x02
mov bh,0x00
mov dh,0x11
mov dl,0x11
int 0x10
mov si, press_key_2 ;display press_key_2 on screen
call print_string
mov ah,0x00
int 0x16
;//////////////////////////////////////////////////////////////////
_skipLogin:
;/////////////////////////////////////////////////////////////
; load third sector into memory
mov ah, 0x03 ; load third stage to memory
mov al, 1
mov dl, 0x80
mov ch, 0
mov dh, 0
mov cl, 3 ; sector number 3
mov bx, _OS_Stage_3
int 0x13
jmp _OS_Stage_3
;////////////////////////////////////////////////////////////////////////////////////////
_OS_Stage_3:
mov ax,0x13 ; clears the screen
int 0x10
;//////////////////////////////////////////////////////////
; drawing window with lines
push 0x0A000 ; video memory graphics segment
pop es ; pop any extar segments from stack
xor di,di ; set destination index to 0
xor ax,ax ; set color register to zero
;//////////////////////////////////////////////
;******drawing top line of our window
mov ax,0x02 ; set color to green
mov dx,0 ; initialize counter(dx) to 0
add di,320 ; add di to 320(next line)
imul di,10 ;multiply by 10 to di to set y cordinate from where we need to start drawing
add di,10 ;set x cordinate of line from where to be drawn
_topLine_perPixel_Loop:
mov [es:di],ax ; move value ax to memory location es:di
inc di ; increment di for next pixel
inc dx ; increment our counter
cmp dx,300 ; comprae counter value with 300
jbe _topLine_perPixel_Loop ; if <= 300 jump to _topLine_perPixel_Loop
hlt ; halt process after drawing
;//////////////////////////////////////////////
;******drawing bottm line of our window
xor dx,dx
xor di,di
add di,320
imul di,190 ; set y cordinate for line to be drawn
add di,10 ;set x cordinate of line to be drawn
mov ax,0x01 ; blue color
_bottmLine_perPixel_Loop:
mov [es:di],ax
inc di
inc dx
cmp dx,300
jbe _bottmLine_perPixel_Loop
hlt
;//////////////////////////////////////////////
;******drawing left line of our window
xor dx,dx
xor di,di
add di,320
imul di,10 ; set y cordinate for line to be drawn
add di,10 ; set x cordinate for line to be drawn
mov ax,0x03 ; cyan color
_leftLine_perPixel_Loop:
mov [es:di],ax
inc dx
add di,320
cmp dx,180
jbe _leftLine_perPixel_Loop
hlt
;//////////////////////////////////////////////
;******drawing right line of our window
xor dx,dx
xor di,di
add di,320
imul di,10 ; set y cordinate for line to be drawn
add di,310 ; set x cordinate for line to be drawn
mov ax,0x06 ; orange color
_rightLine_perPixel_Loop:
mov [es:di],ax
inc dx
add di,320
cmp dx,180
jbe _rightLine_perPixel_Loop
hlt
;//////////////////////////////////////////////
;******drawing line below top line of our window
xor dx,dx
xor di,di
add di,320
imul di,27 ; set y cordinate for line to be drawn
add di,11 ; set x cordinate for line to be drawn
mov ax,0x05 ; pink color
_belowLineTopLine_perPixel_Loop:
mov [es:di],ax
inc di
inc dx
cmp dx,298
jbe _belowLineTopLine_perPixel_Loop
hlt
;***** print window_text & X char
;set cursor to specific position
mov ah,0x02
mov bh,0x00
mov dh,0x01 ; y cordinate
mov dl,0x02 ; x cordinate
int 0x10
mov si,window_text ; point si to window_text
call _print_YellowColor_String
hlt
;set cursor to specific position
mov ah,0x02
mov bh,0x00
mov dh,0x02 ; y cordinate
mov dl,0x25 ; x cordinate
int 0x10
mov ah,0x0E
mov al,0x58 ; 0x58=X
mov bh,0x00
mov bl,4 ; red color
int 0x10
hlt
;set cursor to specific position
mov ah,0x02
mov bh,0x00
mov dh,0x02 ; y cordinate
mov dl,0x23 ; x cordinate
int 0x10
mov ah,0x0E
mov al,0x5F ; 0x58=X
mov bh,0x00
mov bl,9 ; red color
int 0x10
hlt
;set cursor to specific position
mov ah,0x02
mov bh,0x00
mov dh,0x05 ; y cordinate
mov dl,0x09 ; x cordinate
int 0x10
mov si,hello_world_text
call _print_DiffColor_String
hlt
;set cursor to specific position
mov ah,0x02
mov bh,0x00
mov dh,0x12 ; y cordinate
mov dl,0x03 ; x cordinate
int 0x10
mov si,display_text
call _print_WhiteColor_String
hlt
Write, Run & Share Assembly code online using OneCompiler's Assembly online compiler for free. It's one of the robust, feature-rich online compilers for Assembly language. Getting started with the OneCompiler's Assembly compiler is simple and pretty fast. The editor shows sample boilerplate code when you choose language as Assembly and start coding.
Assembly language(asm) is a low-level programming language, where the language instructions will be more similar to machine code instructions.
Every assembler may have it's own assembly language designed for a specific computers or an operating system.
Assembly language requires less execution time and memory. It is more helful for direct hardware manipulation, real-time critical applications. It is used in device drivers, low-level embedded systems etc.
Assembly language usually consists of three sections,
Data section
To initialize variables and constants, buffer size these values doesn't change at runtime.
bss section
To declare variables
text section
_start specifies the starting of this section where the actually code is written.
There are various define directives to allocate space for variables for both initialized and uninitialized data.
variable-name define-directive initial-value
| Define Directive | Description | Allocated Space |
|---|---|---|
| DB | Define Byte | 1 byte |
| DW | Define Word | 2 bytes |
| DD | Define Doubleword | 4 bytes |
| DQ | Define Quadword | 8 bytes |
| DT | Define Ten Bytes | 10 bytes |
| Define Directive | Description |
|---|---|
| RESB | Reserve a Byte |
| RESW | Reserve a Word |
| RESD | Reserve a Doubleword |
| RESQ | Reserve a Quadword |
| REST | Reserve a Ten Bytes |
Constants can be defined using
CONSTANT_NAME EQU regular-exp or value
%assign constant_name value
%define constant_name value
Loops are used to iterate a set of statements for a specific number of times.
mov ECX,n
L1:
;<loop body>
loop L1
where n specifies the no of times loops should iterate.
Procedure is a sub-routine which contains set of statements. Usually procedures are written when multiple calls are required to same set of statements which increases re-usuability and modularity.
procedure_name:
;procedure body
ret