Hello,

I'm not sure if this is the right forum to post this in but.. I'm writing a 6502 assembler and have a question about labels. Having looked at hex dumps it does not appear to be addresses, I'm a bit confused about how this works. I have tried to search for the info but my search terms might have been to general. Any insight into this would be appreciated, thanks.

Are you looking for what the branches to labels assemble? The branch instruction's operand is a single byte, specifying a relative branch distance, up to 127 bytes forward or 128 bytes backward, zero being the byte following the operand of the branch instruction. I don't know if that's what you're looking for. The label itself is only used by the assembler, and does not take any space at all in the final code that you would see in the hex dump.

Garth, he may be wondering how the label gets internally used in the assembler. In that case, a (usually) 16 bit value is associated with the label, usually in a separate array maintained in core or in a temp file on the disk. The meaning of the value would depend on the context in which it is used. It might be an address or a constant (e.g., a register mask or offset).

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

Garth thanks, I suspected it was something like an offset, dividing the byte of the operand into a negative or positive offset makes sense to what I saw in the hex dump. BigDumbDinosaur, right now I parse each row of assembly source into a hash. I'm thinking about counting the address relative from from the first row and give the labels 'key' the current address as 'value'. Then I can get the offset by subtracting the new address from the original address when ever the label re-appear in the source. Thank you guys.

Foo, if you run the raw dump through a dissembler, it comes out with readable code with address labels such as A4367 for an address used. You can then renamed those labels as you discover the functions.

Having fun right now doing that with Asteroids. The code project is woefully incomplete.

http://www.ionpool.net/arcade/astcode/a ... oject.html

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"My biggest dream in life? Building black plywood Habitrails"

I did an almost fully commented disassembly of asteroids a couple of years ago.

Lee.

Lee, do you still have it? My head tech at work (supervisor) is keen on an Asteroids with a much higher speed fire power. I've still been trying to play round with the dissembly but tis a slow one. First experiment got the rocks moving 4 times as fast

Email is nightmartony@yahoo.com.

Thanks!

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"My biggest dream in life? Building black plywood Habitrails"

whoops, nightmaretony

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"My biggest dream in life? Building black plywood Habitrails"