RE: BASIC for the CBM-II/8088

Hallo Michał,


> If so, how do you access the screen data?

I don't read the screen actually, I read the table I mentioned later. At this moment I limit the length of a BASIC line to 80 chars and the end effect is more or less that I keep a copy of the screen memory in the memory handled by the 8088.


> Or do you just allow entering one line at a time (like MS-DOS command line)?

That is indeed what I do in my OS project. I just extended the idea.


> If you want to have fun coding it in assembler, you may do it, but it will be lots of work.

It sounds if I have other means to code it in. I know Linux is coded in C down to a very low level. So what could I do here? And assume it is loaded and started by the piece of code on the boot sector.
One question: what about the size of the compiled program? 


> Also, Commodore BASIC does _not_ tokenize variable names in the program. They are always stored verbatim, and you should do the same.

But I need to make a look-up table that contains the value. Which means I have to use the name again to identify the entry. By using a code I save space. OK, not much, so I already have been thinking about skipping using this code thing. It also saves on needed code.

 
> I would definitely advise against allocating a fixed length for strings.

But that would mean I have to implement "garbage collection". 


> What I would do is to store the program text growing upwards from the bottom of memory, and the variables growing downwards from the top of memory.

I certainly have a look at it.




Hallo Mia,


Thank you for you explanation!


> Btw if you write your own basic, please let it be able to use integers even in calculations, for speed reasons.

I already had the same idea.


> Btw maybe it would be a good idea to patch some existing basic instead?

I decided to start from scratch. A good idea? I don't know. FYI: the moment I come to code the actual BASIC commands, I'll use the source code of the C64/128 as guide.




Hallo Steve,

> I started my PC programming using GWBASIC then QuickBASIC and ...

Except possible direct screen accesses, I don't have any idea why they should not run under MS-DOS on the CBM-ii/8088.


Met vriendelijke groet / With kind regards, Ruud Baltissen

www.Baltissen.org







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