Help/info needed

Hallo allemaal,


I have programmed a lot in assembly for the Commodore but thinking back 
of what I did, about 99% concerned the Commodore drives. Hardly the 
computers.

So I could do with some help or info on two items, please:

- Checking if a device is present. Of course I did some homework. At 
$F237 starts the routine for 'opening a channel for input'. I have to 
provide a secondary address, which is $60 IMHO, and at $F249 StatusIO, 
serial status byte at $90 should be checked. Bit 7 tells us whether the 
device is present or not.
Is this good enough or did I miss something?

- Checking if a file is present. And here I have an idea what to do but 
I'm not happy with it. I can start to load the file and when getting the 
first byte I know it exists. But I have no idea how to end the whole 
process in a clean way.
Another routine I ran into is 'Input a byte from channel' at $F157 which 
results in reading a byte at $F1B5. But how to get there is not 
completely clear (yes, open a file, but how in assembly) but also here: 
how to end it a a neat way.

I hope you can help. Thank you very much in advance

-- 

Kind regards / Met vriendelijke groet, Ruud Baltissen

www.Baltissen.org