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@echo on | |
echo Bulding bin file... | |
nasm loader.asm -f bin -o loader.bin | |
echo Writing bin file to ploppy | |
partcopy loader.bin 0 200 -f0 |
# Build bin file | |
nasm loader.asm -f bin -o loader.bin | |
# Write bin file to floppy | |
dd if=loader.bin bs=512 of=/dev/fd0 |
[BITS 16] ;Tells the assembler that its a 16 bit code | |
[ORG 0x7C00] ;Origin, tell the assembler that where the code will | |
;be in memory after it is been loaded | |
MOV SI, HelloString ;Store string pointer to SI | |
CALL PrintString ;Call print string procedure | |
JMP $ ;Infinite loop, hang it here. | |
PrintCharacter: ;Procedure to print character on screen | |
;Assume that ASCII value is in register AL | |
MOV AH, 0x0E ;Tell BIOS that we need to print one charater on screen. | |
MOV BH, 0x00 ;Page no. | |
MOV BL, 0x07 ;Text attribute 0x07 is lightgrey font on black background | |
INT 0x10 ;Call video interrupt | |
RET ;Return to calling procedure | |
PrintString: ;Procedure to print string on screen | |
;Assume that string starting pointer is in register SI | |
next_character: ;Lable to fetch next character from string | |
MOV AL, [SI] ;Get a byte from string and store in AL register | |
INC SI ;Increment SI pointer | |
OR AL, AL ;Check if value in AL is zero (end of string) | |
JZ exit_function ;If end then return | |
CALL PrintCharacter ;Else print the character which is in AL register | |
JMP next_character ;Fetch next character from string | |
exit_function: ;End label | |
RET ;Return from procedure | |
;Data | |
HelloString db 'Hello World', 0 ;HelloWorld string ending with 0 | |
TIMES 510 - ($ - $$) db 0 ;Fill the rest of sector with 0 | |
DW 0xAA55 ;Add boot signature at the end of bootloader |
Why 16 bit?
Because it is simple to load 16 bit code. Then you can switch CPU to 32/64 bit mode, use protected mode and etc.
Thanks
Can smbody help? How I might to call my extern C function from assembly code?
Can smbody help? How I might to call my extern C function from assembly code?
Just add extern functionName
and call functionName
wherever needed. Make sure to link the files first
Can smbody help? How I might to call my extern C function from assembly code?
Just add
extern functionName
andcall functionName
wherever needed. Make sure to link the files first
Don't forget to setup 32 bit mode or compile your c for 16 bit, and use an appropriate linker
Can smbody help? How I might to call my extern C function from assembly code?
Just add
extern functionName
andcall functionName
wherever needed. Make sure to link the files firstDon't forget to setup 32 bit mode or compile your c for 16 bit, and use an appropriate linker
Can you give linker.ld and boot.s
No I don't know how to do it. I just know what to do, and why
Why 16 bit?