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1990-05-11
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103 lines
This file contains documentation for PBPLUS96
(Copyright 1990 by Robert Zale)
=================================================================
PBPLUS96 is a program which can be used in conjuction with PowerBASIC
version #2.00 in order to obtain an additional 96K of memory for compiling
and running programs.
Several conditions must be met in order to use this extra memory:
1. You must have an EGA or VGA graphics card present in your system,
with at least 128K of memory installed on it.
2. No other software or hardware in your system can use the memory
located at A0000..B7FFF hex (except for the graphics card). Note that
some EMS expanded memory drivers or XMS extended memory drivers may
try to use this area of memory. PBPLUS96 makes every attempt to
determine whether another program is using this memory before it takes
control of it, but some programs which use non-standard memory
allocation methods may not be detectable. If you are at all unsure
of which memory areas your applications require, do not execute this
program in conjunction with them. If an undetected conflict occurs,
using PBPLUS96 will most likely cause your system to crash, resulting
in the loss of all data in memory.
3. You must be in 80-column color text mode (BIOS video mode 3) when
PBPLUS96 is invoked, and you must remain in that mode until you
release the memory by executing PBPLUS96 OFF. PBPLUS96 takes over
the BIOS video interrupt (10 hex) and ignores requests which would
change the video mode or otherwise disturb the 96K memory area.
PBPLUS96 cannot trap direct writes to EGA/VGA graphics registers,
however. Executing a program which performs direct writes while
PBPLUS96 is active will most likely cause your system to crash.
To set aside the 96K of video memory for use by PowerBASIC, execute PBPLUS96
with the ON command-line option:
PBPLUS96 ON
PBPLUS96 takes over the BIOS video interrupt (10 hex). It also places a TSR
(terminate-and-stay-resident) program in memory. This program requires
about 8K and remains in memory until your system is rebooted.
At this point you can use PowerBASIC to compile and/or run programs.
Remember that your programs cannot change the video mode (in order to
perform graphics, for instance) or do anything else which would cause the
memory from A0000..B7FFF (hex) to be disrupted. Attempting to do so may
cause unpredictable results, quite possibly including a system crash. Your
programs may take over interrupt 10 (hex), but they must restore it to its
original value before terminating. Failure to do so will prevent the later
deallocation of the 96K memory area, eventually necessitating a system reboot
to restore your normal memory configuration.
When you are finished using the extra memory, execute PBPLUS96 with the OFF
command-line option:
PBPLUS96 OFF
This will restore the video interrupt (10 hex) to where it was pointing
before PBPLUS96 ON was executed, and will return the 96K of video memory
to the EGA/VGA card. The TSR will remain in memory. At this point, the
video system will appear to be "normal" to any programs that are subsequently
executed; that is, you can perform graphics or any other video operations
which would otherwise disrupt the PBPLUS96 memory.
To acquire the memory again later, simply execute PBPLUS96 ON again. To
release it, execute PBPLUS96 OFF.
Due to the nature of PBPLUS96's interaction with your video hardware and
BIOS software, we cannot guarantee that it will work properly with all
programs in all circumstances. In particular, executing a program which
deals with the video card or the BIOS directly, or which SHELLs to a program
that does, may cause unpredictable results. In order to limit the
possibility of such conflicts, you should activate PBPLUS96 only when it is
necessary in order to compile or run a large program. Once the compile or
run is finished, you should execute PBPLUS96 OFF to release the video memory.
As an example, you may wish to set up a batch file which takes the memory,
uses the command-line compiler (PBC.EXE) to compile a program to an .EXE
file, pauses after compilation, then releases the memory:
PBPLUS96 ON
PBC -CE %1 %2 %3 %4 %5 %6 %7 %8 %9
PAUSE
PBPLUS96 OFF
The pause is necessary so that you can see any error messages or statistics
displayed by PBC.EXE, before PBPLUS96 clears the screen.
A similar batch file runs the PB.EXE compiler:
PBPLUS96 ON
PB %1 %2
PBPLUS96 OFF
In this case, pause is not neccessary, as PB.EXE does not exit to DOS after
compilation.
============================================================================