Re: Help with BASIC....

[nparker@cie-2.uoregon.edu (Neil Parker)]

In article <4k283a$in4@wormer.fn.net> demstar@fn.net (Invalid Opcode) writes:
>	I have a series of files that appear mostly AppleBASIC, with the
>exception of a very strange token.  The token is interpreted as the &
>token by AppleBASIC, but it causes syntax errors the way it's used.
>Some examples of usage are:
>
>100 &B,1,38,1,23
>200 &5,253+DD
>300 &G,3-PEEK(32),21
>
>	It seems to take an arbitrary number of parameters, can take variable
>names and numeric constants in any order, and can use the results of
>other tokens as parameters.  However, all three of these examples
>cause syntax errors under AppleBASIC.
>
>	So what I'm wondering is if this is from that "Integer BASIC" that
>I've seen mentioned once or twice.  Or maybe something else.  All
>other tokens in the program are straight AppleBASIC except these &
>things.  Any useful help will be much appreciated.

What you have there is an example of Applesoft's "ampersand" command.
Ampersand, or "&", is actually a valid Applesoft command, intended to be
used for adding new commands to BASIC.  When Applesoft sees the "&"
command, it calls a machine-language program in RAM.  The machine-language
program can then take control of the BASIC interpreter briefly, recognize
whatever commands or expressions follow right after the "&", and generally
do whatever it wants with them.

The RENUMBER program on the DOS 3.3 System Master disk uses the "&" to add
a renumber command to BASIC.  Typing "RUN RENUMBER" installs the renumber
command, and then you can load your own program, and type commands like

     & F5, I5

to renumber your program starting at line 5 and increasing by 5.

RENUMBER isn't the only thing out there that uses "&" to extend Applesoft.
Over the years countless "&" packages have been written and published,
adding just about every conceivable new command to BASIC.


But before you can use "&" for anything at all, you must first load the
machine-language program the implements the new commands.  This is usually
done by POKEing machine code into memory from BASIC (if it's not too long),
or BRUNning a file from disk.

Heaven only knows what the examples from your program were supposed to do.
The only way to get them to work would be to load the machine-language
program that they're intended to work with.

             - Neil Parker
-- 
Neil Parker, nparker@{cie-2,cie}.uoregon.edu, http://cie-2.uoregon.edu/~nparker

     "I was going to be a neo-deconstructivist but Mom wouldn't let me."
                                     -- Calvin and Hobbes, 7/13/1995