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1991-07-10
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PMCHKSUM
---------
A PM File CRC checker
INTRODUCTION
------------
This program is a file CRC checker that runs under PM
(Presentation Manager) of OS/2. It assigns a unique
number (a CRC) to each file of the extensions you specify
and stores it. The next time you run PMCHKSUM, it calculates
the CRC and compares it the the stored CRC. If they are
different, an error message is produced. This may be a good
second line of defense against Virii infecting your system.
The first line of defense, of course, is practicing safe computing.
PMCHKSUM spins off low-priority idle-time threads to do the
calculations and comparisons. As a result of this, PMCHKSUM
does not interfere with normal work. PMCHKSUM also comes with
its' own timer, options that allow it to be run from a
CHRON-like utility, full on-line help and hardcopy reporting.
DISCLAIMER
----------
The Program is supplied "AS IS" without any warranty of any kind,
either expressed or implied, including, but not limited to, the
implied warranties of merchantability and fitness for a particular
purpose.
In no event shall Robert Mahoney be liable for any damages, either
direct or consequential, caused by the use, or inability to use,
this program, even if Robert Mahoney has been advised of the
possibility of such damages.
ACKNOWLEDGMENTS
---------------
The logic for the calculating of the CRC is taken from an article
by David Schwaderer in the April 1985 issue of PC Tech Journal.
NOTE
----
This program has been tested with:
Software:
IBM OS/2 EE and SE v1.3 (does not run on v1.2)
Hardware:
IBM Model 70-121 with 6MB.
386 clone with 6MB.
PMCHKSUM - A PM File CRC Checker Page 2
USAGE
-----
To use this program enter START PMCHKSUM at the OS/2 command prompt
or add it to a group. The internal timer is initially disabled
so it will wait for user input. The default extensions are
EXE,DLL, and SYS. You can add to this list or change the list
(see the on-line help for more details). Pressing START will
begin the scan. The Status Message listbox will display status
messages, such as time of Scan starting and CRC entry added.
The Error messages listbox will issue messages such as a CRC
has changed or an CRC entry could not be added. Pressing
CANCEL will cancel the scan, EXIT will prompt you for a confirmation
and exit the application, HELP will give you on-line help, and
OPTIONS will bring up the Options dialog.
For a more through explanation please see the on-line help.
START
-----
The program is started by simply typing "PMCHKSUM" on the
command line. Parameters are neither necessary nor recognized.
The program can be inserted very easily into a group of the
PM program starter. It can be invoked from there with a
single "Double-Click".
PMCHKSUM looks in the working directory for the file containing
the CRC's. If it doesn't find it, it will create a new file
and store the current CRC's there. If you start PMCHKSUM from
different subdirectories, you will have multiple files named
PMCHKSUM.IDX and waste alot of space. You also will not get
the benefit of the CRC checker.
PMCHKSUM - A PM File CRC Checker Page 3
PERFORMANCE HINTS
-----------------
1) Exit other applications that depend on low-priority threads
such as CPUMETER and DESKPIC. Since PMCHKSUM uses low-priority
threads, the contention for thread time between other programs
that primarily uses low-priority threads will cause PMCHKSUM and
the other programs run much slower.
2) As mentioned before, start PMCHKSUM from the same directory
all the time. This will avoid having multiple data files on
your disk.
3) On a 120MB disk containing 32 .SYS's, 200 .DLL's and 358 .EXE's
the data file takes up 24K.
4) Do not SHUTDOWN or CLOSE while PMCHKSUM is running a scan.
Press CANCEL first. Although I've had no reported problems
with this, it's better to be safe than to have a corrupted
data file.
REGISTRATION
------------
This program is released as SHAREWARE. There is no difference
between the REGISTERED version and the SHAREWARE version.
I do not believe in CRIPPLE-WARE nor ANNOYING-WARE (the kind
of program that constantly reminds you via message box that you
still have not registered). I believe that honest people will
register a program if they use it. But, depending on the response,
I may change my policy.
I will simply ask everybody who is willing to continue the
use of this program in the future to send the filled regist-
ration form back to me. This will encourage me to continue
to write useful OS/2 PM programs.
The registration cost of this program is only:
US $15 for individuals.
$25 per copy for companies with 25 or less employees.
$40 per copy for companies with 26 or more employees.
Yes, ----> $15 <----- will get you registered and you will be able
to sleep better at night.
PMCHKSUM, A PM File CRC Checker Page 4
FUTURE ENHANCEMENTS
-------------------
To give you an idea of some potential future enhancements:
1) Search for files by Extended Attributes (EA's)
e.g. DYNAMIC LINK LIBRARY or EXECUTABLE
2) Sizeable dialog box with auto-adjusting child windows
and fonts. This way you can make the window as big
or as small as you want and still see all of it.
3) Re-write the CRC calculation in assembler. This
will speed up the calculation but value is questionable
in a low-priority thread.
4) Eliminate non-existent files from the data file.
Currently the data file does not get cleaned up.
e.g. if you delete a file from your disk, it will stay
in the datafile forever.
5) Remember where the window was placed and the size of it.
I would love to hear any and all other suggestions.
I can be reached on:
Fidonet OS/2 echos
BIX as RMAHONEY
Prodigy as KBFN97A
my address is on the next page
(send me a letter with a check! <g> )
PMCHKSUM, A PM File CRC Checker Page 5
Date: __________ __ ,19__
Robert Mahoney
27 East Jackson Ave
Babylon, New York 11702
Subject: Registration PMCHKSUM
Yes, I want to register PMCHKSUM. I know that this program is
released without any kind of guarantee.
Enclosed is the registration fee of
_ Individual - $15
_ Company < 25 employees __ copies at $25/copy = $ ___
_ Company > 25 employees __ copies at $40/copy = $ ___
Name: _______________________________
Company
Name (opt): _______________________________
Street: _______________________________
City: _______________________________
State: _______________________________
ZIP : _______________________________
__________________________________
(signature)