Question

I am trying to print character from boot loader using code

[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 AL, 65
CALL PrintCharacter
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

TIMES 510 - ($ - $$) db 0   ;Fill the rest of sector with 0
DW 0xAA55           ;Add boot signature at the end of bootloader

As directed in Writing Hello World Bootloader. But it just hangs without printing anything. How can we debug this ? I have successfully created hanging boot loader using following code

[BITS 16]   ;tell 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

JMP $       ;infinite loop

TIMES 510 - ($ - $$) db 0   ;fill the rest of sector with 0
DW 0xAA55           ; add boot signature at the end of bootloader

I am testing my code on VMware 3.0.0 build-203739.

Answer 1

For debugging real-mode X86, you can try the debugger integrated with Dosbox.