[Coco] Returning a string to basic ?

Arthur Flexser flexser at fiu.edu
Tue Sep 20 17:43:21 EDT 2011

I'm going from hazy memory on this...

I'm assuming the string is at a known address and has a known length.

What you need to do is this:

Define a dummy string in the Basic program with some statement like S$="A".

Then use the Basic VARPTR function to find the address of Basic's
pointer to the string:  ST=VARPTR(S$).

At the address now contained in ST is a 5-byte string specifier.  The
first (I think) byte is the string length, and the 3rd and 4th (?)
contain the address of the string data.
(The other 2 bytes of the 5-byte identifier are unused.)

Using POKEs, you can modify these 3 bytes to insert the length and
address of the string you want Basic to know about, which will then be
referenced by S$.

Hope that does the trick for you!


On Tue, Sep 20, 2011 at 5:08 PM, Phill Harvey-Smith
<afra at aurigae.demon.co.uk> wrote:
> Hi all,
> I'm developing a SD/MMC interface for the Dragon and CoCo, and need a method
> of returning a string to basic so that I can add a function to (for example)
> return the current working directory on the card.
> How would I go about this ?
> Cheers.
> Phill.
> --
> Phill Harvey-Smith, Programmer, Hardware hacker, and general eccentric !
> "You can twist perceptions, but reality won't budge" -- Rush.
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