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APPLE/// INVOKABLE MODULES
by Alan Anderson
In the last issue we talked about how SOS calls are put
into Assembly language programs, and how to link those
Assembly language programs to Pascal programs. This
issue, by popular demand, we'll reveal how to go about
writing invokable modules to enhance the power of Business
BASIC. The things mentioned at the end of last issue
will appear next time (unless, of course, popular demand
again dictates otherwise).
But First, a Word 'from our Sponsor ...
Great news for all us Apple I 11 programming hackers.
The new edition of the Standard Device Drivers Manual is
out, and it's superb. It includes in-depth (and I mean indepth)
discussions of what each of the standard device
drivers can do. The list of standard drivers includes .CON­
SOLE, .GRAFIX, .PRINTER, .RS232, and .AUDIO. The
power in these drivers, particularly .CONSOLE and
.GRAFIX, is incredible. The information included in this
manual is extremely complete. We'll talk about some of the
secrets it reveals later in this article.
The PERFORMing Arts
The ink was hardly dry on the preliminary Business
BASIC Reference Manual (yep, they've upgraded that one,
too) before the good old Apple II crew noticed that horrible
oversight in the new BASIC: they left some things out,
specifically PEEK POKE, and CALL. To Apple II programmers,
this seemed like something very close to
betrayal. The PEEK, POKE, and CALL statements meant
unlimited expandability for Applesoft and Integer BASIC.
Anything that couldn't be done in the high-level language
could be written in Assembly language and linked to the
main program with these statements. Their absence from
Business BASIC seemed to mean that the language was
forever locked up.
Of course, that was not the case. Upon closer examination,
the new BASIC had a couple of unfamiliar new statements:
INV