Re: running .system files from BASIC

[dalloff@gcfn.org (Dave Althoff Jr)]

Simon Williams (see_sig_for_valid_email@no.spam) wrote:
: "Bill Garber" <willy46pa@comcast DOT net> wrote:

: > You need the Semi-Colon after D$ otherwise
: > it'll think D$"-xxxxxxxx.SYSTEM" is all one
: > variable.

: Really? I thought that was just a convention to make reading the listing
: easier on humans. I could well be wrong, though...

In Applesoft you don't need the semicolon to separate a variable from a
literal.  Applesoft is smarter than those modern languages that way.  8-)

There is an important restriction, though...

Many lazy programmers in DOS 3.3 would set...

D$=CHR$(13)+CHR$(4)

...and that won't work at all under ProDOS.  The ^D has to be the first
character printed.  Under DOS 3.3, it just had to be the first character
printed on the current line; under ProDOS it also has to be the first
character in the print instruction.

Personally, I don't use D$ for that purpose.  Why waste a perfectly good
variable to store one byte?  More important, why use a variable for a
constant?  Instead, I use...

PRINT CHR$(4);"DOS COMMAND"
Hmmm...I'm curious...how does this work out memory-wise...?

METHOD A:
D$ = CHR$(4)
12 3 4    56

PRINT D$;"DOS COMMAND"
7     89AB

That's 11 bytes, plus another six or seven (IIRC) to store the string
variable...for one use, that's 18 bytes, 5 for subsequent uses.

METHOD B:
PRINT CHR$(4);"DOS COMMAND"
1     2    3456

That's only 6 bytes on each use.  So if you use less than 11 DOS commands
in the program, you come out ahead.  That's nothing compared to Method C:

METHOD C:

PRINT "^DDOS COMMAND"
1     23

That's only 3 bytes per use.  Except that where you see that a lot is in
program listings, where it doesn't take 3 bytes, it takes 65 bytes because
instead of doing it 'right' with method A or B, they add a needless comment:

PRINT "^DDOS COMMAND":REM THERE IS AN INVISIBLE CONTROL-D AFTER THE FIRST
QUOTE MARK.


--Dave Althoff, ][.
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