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SLEEPER.DOC
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SLEEPER
by Eric Tauck
October 25, 1989
SLEEPER is a memory resident utility that automatically blanks a
screen after a certain period of keyboard inactivity or upon command
by the user. This is useful in preventing screen 'burn-in' or hiding
the contents of the screen from prying eyes. SLEEPER requires a
standard IBM PC or compatible computer running PC or MS DOS version
2.0 or higher and uses about 750 bytes of memory.
NOTE: there are different versions of SLEEPER for different adapter
types. Only run the version of SLEEPER that matches the computer's
adapter. See the end of this document for more information on the
different versions of SLEEPER.
SLEEPER must be made resident before it can blank the screen
automatically. This is done by running SLEEPER from the DOS command
line. A single numeric parameter may be specified to set the amount
of time (in seconds) before blanking the screen. If the parameter is
absent, SLEEPER will blank the screen after five minutes (300
seconds).
Once installed (i.e. made resident), SLEEPER constantly monitors the
keyboard and system clock. If no key is pressed for the specified
amount of time, SLEEPER blanks the screen. SLEEPER will make the
screen visible the moment any key is pressed. The pressed key is NOT
absorbed by SLEEPER, but is passed through to the system.
The resident SLEEPER can be controlled by running the SLEEPER program
or with special keystroke commands. The keystroke commands will only
work when an application is expecting keyboard input. For instance,
during a long compile, the keyboard commands will not work because
most compilers don't poll the keyboard.
If the screen is explicitly blanked (by running SLEEPER with the H
option or pressing ALT-CTRL-H when resident), it will remain so until
it is explicitly un-blanked (by running SLEEPER with the V option or
pressing ALT-CTL-V when resident) or by resetting the timer (by
running SLEEPER with the R option or pressing ALT-CTRL-R when
resident).
The screen can be blanked without installing SLEEPER by running it
with the H option. The screen will remain blank until SLEEPER is run
again using the V option.
SLEEPER will blank the screen in all text and graphics modes. When
the screen is blank, the computer continues to operate normally. You
can continue to type commands to an application or DOS, even if you
are unable see what you're typing.
Non-Resident Command Line Options
---------------------------------
SLEEPER ?
Display a brief help screen.
SLEEPER nnn
Install SLEEPER with a timer value of 1 to 3600 seconds. If this
number is absent, SLEEPER will be installed with a value of 300
seconds (five minutes). Note that the number 'ticks' are displayed
upon installation, not seconds. Ticks occur at about 18.2 per
second and are what SLEEPER actually uses to measure the passage of
time.
SLEEPER H
Force the screen hidden (i.e. blank). The screen will remain hidden
until the screen is forced visible with the V option below.
SLEEPER V
Force the screen visible. Only useful if the screen has been forced
hidden with the H option above.
Resident Command Line Options
-----------------------------
SLEEPER ?
Display a brief help screen.
SLEEPER nnn
Set a new timer value. The range of legal values is 1 to 3600, the
same as when installing SLEEPER. As when installing, the number of
ticks (not seconds) are displayed.
SLEEPER H
Force the screen hidden (i.e. blank). The timer is disabled and the
screen remains blank until it is forced visible or the timer is
reset.
SLEEPER R
Reset the timer. The internal timer is reset as if a key was
pressed. If necessary, the timer is restarted and the screen is un-
blanked.
SLEEPER T
Force a timeout. The internal timer is set so the screen will blank
after one second. Once the screen is blanked, it will be un-blanked
as soon as any key is pressed.
SLEEPER U
Uninstall SLEEPER. This command removes SLEEPER from memory.
Sometimes
SLEEPER cannot be removed if another TSR has been installed after
SLEEPER.
SLEEPER V
Force the screen visible. The timer is disabled and the screen
remains visible until it is forced hidden or the timer is reset.
Resident Keyboard Commands
--------------------------
ALT-CTRL-H
Force the screen hidden. Same as SLEEPER H above.
ALT-CTRL-R
Reset the timer. Same as SLEEPER R above.
ALT-CTRL-T
Force a timeout. Same as SLEEPER T above.
ALT-CTRL-V
Force the screen visible. Same as SLEEPER V above.
Usage Notes
-----------
SLEEPER is usually installed automatically in the AUTOEXEC.BAT file
when the computer is booted up.
Controlling SLEEPER from the command line is typically done from batch
files to modify SLEEPER before loading an application and then to
restore SLEEPER once the application has terminated. Since SLEEPER
cannot detect input from a mouse or joystick, you may want to force
the screen visible before running an application which primarily uses
a mouse or joystick for input.
SLEEPER doesn't work well with all applications, particularly
applications that are timing or video sensitive (like games for
instance). If you think there is a conflict between an application
and SLEEPER, you can always uninstall SLEEPER before running the
application and then reinstall SLEEPER once the application has
terminated.
SLEEPER monitors the shift keys (SHIFT, ALT, and CTRL) as well as all
of the 'normal' keys. A shift key can be used to restore a blanked
screen without passing a keystroke to the currently executing program.
Releasing a pressed key has a the same effect as pressing a key, thus
if a key was being held down when SLEEPER decided to blank the screen,
the screen will be un-blanked as soon as the key is released.
Similarly, if you use the forced timeout keystroke command (ALT-CTRL-
T) and hold the ALT or CTRL keys down for more than one second, the
screen will be un-blanked as soon as you release either key.
SLEEPER only works with VGA adapters, however two special versions of
SLEEPER, SLEEPERE and SLEEPERM, are provided that should work with EGA
and monochrome adapters respectively. SLEEPERE blanks the screen by
setting the palette registers to black. Because setting the palette
registers is not an instantaneous operation, keystrokes can be lost
when blanking or restoring the screen. Only run the version of
SLEEPER that matches the computer's adapter, though it should be okay
to run SLEEPERE on a VGA adapter.