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BLANKS.DOC
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1989-04-20
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18KB
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365 lines
-------------------------------------------
For personal, noncommercial use only
May not be sold - All rights reserved
-------------------------------------------
Copyright (C) 1988, 1989 by FM de Monasterio
BLANKs version 1.6b
--------------------
BLANKs is an MS-DOS/PC-DOS based, resident program that blanks the
screen after a preselected interval in the absence of a keypress. This
interval can be selected from 1 to 60 minutes. A selection higher than
60 minutes is set to 60. Selecting 0 minutes disables screen blanking;
blanking can be enabled by re-invoking with an interval of 1 to 60 min.
BLANKs is a TSR. When resident, it uses less than 700 bytes; it can be
invoked repeatedly to change its settings without resulting in multiple
copies to memory. BLANKs intercepts interrupts 8h, 9h, and 10h, and is
a well behaved resident, intended to run under MS-DOS or PC-DOS version
2.0 or later.
----------------
OPERATION:
Screen blanking is obtained by direct commands to the hardware (video
controller) to turn off/on the video signal. This is a fast method that
operates successfully in the IBM PC/XT, PC/AT and in some IBM compatible
computers installed with MDA, CGA, EGA, VGA, and Hercules video adapters
or with IBM compatible adapters from other manufacturers.
NOTICE In some nonIBM microcomputers the program may not work and it
------ should NOT be used with other video adapter types unless they
are compatible with the IBM adapter at the register level (as
it is possible that some of these adapters might be damaged).
The resident component of BLANKs intercepts interrupts 8, 9, 10h and 33h
that subserve respectively the time-of-day, keyboard, BIOS video and (for
programs following the Microsoft's Mouse format) mouse operations.
BLANKs will fail to operate if access to interrupts 8 and 9 is denied by
another program or resident loaded after BLANKs. This might occur with a
few communication and (older) word processing programs.
- Interrupt 8 is called 18.2 times/s to update the computer time-of-the-day
counter (which is stored in the BIOS data area). Since a timer interrupt
can thus only operate within a period of about 55 ms or less (*including*
the overhead of DOS and other programs hooking on the timer), the program
uses direct commands to the hardware, written in assembly language, which
are issued (when needed) after the original timer interrupt is served.
- Interrupt 9 is called when a key on the keyboard is pressed (or released).
When the hotkey service is enabled (see switch /H below), BLANKs triggers
blanking of the screen when the default hotkey combination (CTRL-B in non-
shareware versions) is pressed. The hotkey code is then removed from the
keyboard buffer. Other keys are passed along for keyboard processing and,
if a blanking had occurred, the screen is restored.
- Interrupt 10h is called to mediate a number of video subfunctions. Because
such functions are comparatively slow, many programs do not use BIOS video
calls, but make direct writes to the screen (which are not detected by the
resident part of BLANKs).
- Interrupt 33h is used in Microsoft's implementation of calls to the Mouse.
Other drivers, compatible with the Microsoft Mouse format, also implement
at least some of these calls. Some graphics programs, however, do not use
these calls, and their resulting video activity is not detected by BLANKs.
NOTICE To be able to monitor interrupt 33h, BLANKs must be installed
------ *after* the mouse driver program as otherwise the driver will
not allow access to the interrupt. Also note that the driver
for a well known mouse, upon its installation, can freeze the
computer if interrupt 33h is found to be in use; this problem
does not occur with other drivers, e.g. Logitech's MOUSE.COM.
Bypassing Interrupts:
While installed, BLANKs bypasses the interrupt 8 when a blanking interval
of 0 minute has been selected (see below). Interrupt 9 is bypassed only
when both an interval of 0 minute and the switch /H- (see below) have been
selected. When /H- has been selected along with a nonzero interval, just
the hotkey service of interrupt 9 is bypassed. Hence, these two interrupt
activities of BLANKs are bypassed by the "0 /H-" selection; this may be of
use in case of testing potential conflicts with other programs.
Interrupts 10h and 33h are not intercepted when "/K[+]" is specified; when
this switch is not specified, these two interrupts are intercepted but not
monitored unless the switch "/V[+]" is specified.
(In the shareware version, where cloning is available, if a cloned version
has been created with /K+ as the default condition, these 2 interrupts are
bypassed irrespective of whether switches "/K-" and/or "/V+" are specified
or not. To access video activity monitoring, the program must be recloned
with a command line including the "/K- /C" switch selections.)
----------------
USAGE:
From the DOS command line or from a batch file, BLANKs is installed (or,
when already installed, modified) by the command:
BLANKs [?] [min] [/switches]
[?] Invokes a brief help and status display, identifying the type
of adapter for which the program is configured, the current
adapter, and program settings (if installed).
Pressing key <F1> displays further help on using the program.
If the program has not been installed, pressing key <D> shows
the default settings.
[min] Timed blanking interval in minutes. These are the minutes that
the program waits before blanking the screen in the absence of
keyboard activity. Valid selections are 0 or a number in the
range of 1 to 60. The selection of a 0-min interval disables
the timed blanking of the screen; the selection of an interval
larger than 60 defaults to 60 minutes for 2 digit inputs or to
the value (in the valid range) of the first 2 digits in inputs
containing larger numbers.
Null interval defaults to 3 minutes. This value may be changed
by cloning the program (see below).
Several switches are recognized. While shown as being preceded by a "/"
for the sake of clarity, the program accepts any character between space
[ ] and slash [/] as a switch delimiter [!"#$%&'()*+,-.]. Nonrecognized
switches abort loading of the program. Switches are not case sensitive.
NOTE: Options marked with an asterisk (*) are available in the shareware
versions of BLANKs only.
/U Uninstall. Use only when BLANKs was the last resident to be
installed, as otherwise this would create a "hole" in memory.
The request is not honored if vectors to interrupts 8, 9 and
10h have been changed since installation. This can be caused
by a resident installed after BLANKs, or by a prior resident
that changes vectors set by programs installed after it. You
can determine if this is the case by using any of the memory
mapping programs that are available (search for interrupts 8
9 and 10; BLANKs.COM will be shown as an unnamed entry using
736 or 656 bytes, depending on the switch selection.)
/C Clone to disk the current