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Shareware Supreme Volume 6 #1
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swsii.zip
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swsii
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178
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PATCHBAS.ZIP
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PATCHBAS.DOC
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1986-01-21
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78 lines
There was a file called BASICAJR.DOC on the California junior BBS at
1(213)659-7187 that explained how to use Debug to patch BASICA.COM so that it
would run on an IBMPCjr without cartridge basic installed. Usually when you
try to run any version of basic on a jr., you must have cartridge basic
installed. If you don't, you will get a message "Cartridge Required" as
explained on p. A-7 of jr's Basic manual. With this patch, you do not need to
have the basic cartridge inserted; all you need is the patched version of
BASICA on disk.
There are two reasons why running BASICA from disk is a good idea.
First, it lets you use basic even without the special junior cartridge
version, which you might want to do because you haven't got it or because
you have other special purpose cartridges in both slots and want to run a
quick basic program without rebooting the machine.
Second, because of the way cartridge basic checks for whether there is
enough memory on the machine to run basic, if you have over 256K on your junior
you may get an "Out of Memory" statement and won't be able to run basic even if
you know you have 640K. This is because cartridge basic does an Int 12H to get
the total amount of memory, but it only reads the "low byte" returned. This
means that with more than 256K, it may think that it only has 18962 bytes free,
not enough. Disk basic will still run fine in this case. The solution that
most makers of hardware like memory expansions or second drives for the junior
suggest, is to keep a copy of unmodified DOS to run basic with, but that is
very inconvenient. It means, for instance, that you can't run a quick basic
program to set up your printer or keep a log of computer usage when running 123
or a full-size word processor. This patched version will work in those
circumstances.
There are two small problems with this patch.
First, the original patch disabled the "soft" keys, the function keys
that show up on line 25 of the basic screen. (See jr's Basic manual, p. 4-158.)
You would have to type in "RUN" instead of using Fn2. I have written a short
basic program that corrects this; if you run it whenever you start disk basic,
the function keys will work. You might want to modify the function keys after
you take a look at this program and pp. 4-157 to 4-159 in the junior basic
manual; you can set up a function key to clear the screen and return to the
system if you like, or anything else you want. While you are at it, you can
change line 0 of the program to use colors you like; I have just added line 0
because I like those colors on my basic screen. You don't need to do any of
this if you don't mind the lack of soft keys. If you do want to use the soft
keys, to start basic with soft keys enabled type BASICAJR KEY then hit return
key.
Second, cartridge basic has several features and commands that disk
basic doesn't. If a program was designed specifically for cartridge basic on
the jr, it may not run under BASICA. Except for those programs written
specifically for jr's cartridge basic, disk basic should be o.k..
The simplest way to get disk basic is to just rename a copy of
BASICA.COM something like JRBASIC.COM. This works fine if you always keep
your basic cartridge in one of the slots, but if you have two other cartridges
there and try it, you will get the "Cartridge required" message. This patched
version of BASICA must also be renamed; if you just type in BASIC or BASICA,
you will get thrown into the cartridge version. The automatic patch will rename
BASICA BASICAJR.COM (for BASICA jr version). To run disk basic, always
remember to type in BASICAJR; to run it with working function keys, type in
BASICAJR KEY.
To patch your copy of BASICA.COM, you must have copies of the following
files on your disk:
BASICA.COM (program to be patched)
DEBUG.COM (program that does the patching)
PATCHBAS.BAT (program that automates the process)
PATCH.TXT (file that tells debug what to do to basica)
At the DOS prompt, type in PATCHJR; everything else should happen
automatically. When you see the DOS prompt again, you should have a patched
version of disk basic.
John Wager
844 Carpenter
Oak Park, Il.