No Linker Needed?

someprogr · Post by **someprogr** » Thu Dec 27, 2007 4:18 pm

Can anyone tell me why I was able to assemble this bootloader with NASM, and use it without linking it? I don't undertstand.

Heres the link:
http://www.osdever.net/tutorials/hello_btldr.php

Combuster · Post by **Combuster** » Thu Dec 27, 2007 4:59 pm

NASM can "link" by itself

Craze Frog · Post by **Craze Frog** » Fri Dec 28, 2007 6:02 am

A linker takes several object files in format X and combines them into one file in format Y. In your case you only had one object file and format X and Y was the same, so no linking was needed.

Dex · Post by **Dex** » Fri Dec 28, 2007 9:11 pm

Fasm can also link its self.

Red Shaya · Post by **Red Shaya** » Mon Dec 31, 2007 10:29 am

A linker does as it name implies. It LINKS things between objects.
For example, it links a symbol with an actual address. So when you call the function "kprintf"

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    CALL _kprintf

the linker links the symbol "_printf" from your object with the pointer to the kprintf function in another object (its more complicated, but this simple explanation will do for what I'm trying to say).
When you write a bootloader, you don't refer to any symbolic object outside your bootloader. You just run a small piece of code that has all its references hard coded. For example

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    CALL 07D0h:0

So you don't need a linker to resolve any references.