Jan 022018
 
Ram-resident file compressor/decompressor from Ireland. (Compare to DIET from Japan, or Cubit or SQZ.).
File SLIM110A.ZIP from The Programmer’s Corner in
Category Utilities for DOS and Windows Machines
Ram-resident file compressor/decompressor from Ireland. (Compare to DIET from Japan, or Cubit or SQZ.).
File Name File Size Zip Size Zip Type
SLIM.DOC 56064 16075 deflated
SLIM.EXE 21562 13114 deflated
SLIMDEMO.BAT 2688 973 deflated
VENDOR.DOC 2816 1264 deflated

Download File SLIM110A.ZIP Here

Contents of the SLIM.DOC file









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SL SL IM IMSL SLIM
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MSLIMSL LI MS MS LI MS
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MSL IMS MS LI LI LI
LIMSLIMS SLIMSLIMSL SLIMSL IM IM
MSLIMS LIMSLIMSLI LIMSLI MS MS




_______ _______ _____________________ ___________

S L I M F i l e C o m p r e s s i o n S y s t e m
_______ _______ _____________________ ___________



U s e r M a n u a l



Version 1.10A









Copyright (C) Dominic Herity 1988,1991
_______
____|__ | (R)
--| | |-------------------
| ____|__ | Association of
| | |_| Shareware
|__| o | Professionals
-----| | |---------------------
|___|___| MEMBER
S L I M U s e r M a n u a l Pg 1







Copyright (C) Dominic Herity 1988,1991
All rights reserved

This software and manual are supplied "as is" and without
warranties as to performance or merchantability. This software is
supplied without any expressed or implied warranties whatsoever.
No warranty of fitness for a particular purpose is offered. Any
liability of seller or manufacturer will be limited exclusively
to product replacement or refund of the purchase price. Dominic
Herity further reserves the right to alter the specifications of
the software and contents of the manual without obligation to
notify any person or organization of such alterations.

SLIM is a "shareware program", and is provided at no charge to
the user for evaluation. Feel free to share it with your friends,
but please do no give it away altered or as part of another
system. If you find SLIM useful, and that you continue to use it
after a reasonable trial period, you must make a registration
payment to the author. All registered users will receive a copy
of the latest version of SLIM, along with the other benefits of
registration. See Section 10 of this manual for more information.

Commercial users of SLIM must register and pay for their copies
of SLIM within 30 days of first use, or their license is
withdrawn. Site license arrangements may be made by contacting
Dominic Herity.

Anyone distributing SLIM for any kind of remuneration must have
authorization from Dominic Herity at the address below.
Authorization will be automatically granted to associate members
of the Association of Shareware Professionals. Authorized
distributors will receive prompt upgrades.

Dominic Herity, PO Box 3038, Dublin 4, Ireland.
CompuServe: 100016,3477 Internet: [email protected]

This program is produced by a member of the Association of
Shareware Professionals (ASP). ASP wants to make sure that the
shareware principle works for you. If you are unable to resolve a
shareware-related problem with an ASP member by contacting the
member directly, ASP may be able to help. The ASP Ombudsman can
help you resolve a dispute or problem with an ASP member, but does
not provide technical support for members' products. Please write
to the ASP Ombudsman at P.O. Box 5786, Bellevue, WA 98006 or send
a Compuserve message via easyplex to ASP Ombudsman 70007,3536
S L I M U s e r M a n u a l Pg 2






















A C K N O W L E D G E M E N T S


Thanks to LJF Berenson, Adrian Bivar, John Cockings, Kam Ho,
Panos Milonas, Alan Pink, Sam Smale, Charles Stross, Peter
Tetley, Bertold Tromm and Charles P White, for bug reports and/or
suggestions for improvement of SLIM. I was encouraged by their
enthusiasm and constructive criticism.

Many thanks to Brian Doody, Kevin McGoldrick, Imelda Herity,
Michael Feehily, Tony McGinty and Kieran Boyce, each of whom
contributed helpful suggestions and observations to this product.

All thanks to my wife, Teresa, for all her help, support,
encouragement and faith when I spent evenings and weekends stuck
in front of a computer with no visible results.
S L I M U s e r M a n u a l Pg 3

















C O N T E N T S



Section Subject Page


1.0 Introduction 4

2.0 Getting Started 5

3.0 Compressing Files 8

4.0 Accessing Compressed Files 11

5.0 De-compressing Files 15

6.0 Technical Information 16

7.0 Error and other Messages 17

8.0 Technical Support 19

9.0 Version History 20

10.0 Registration 21
S L I M U s e r M a n u a l Pg 4


1.0 I N T R O D U C T I O N


SLIM is a powerful file compressor with RAM resident transparent
expander, which gives painless access to compressed files. This
is done by intercepting DOS calls, allowing applications to read
compressed files just as before. So there is no need to worry
about technicalities like archives. Just put a command to load
SLIM into the AUTOEXEC.BAT file and forget it.

A proprietary algorithm significantly compresses almost all the
files found on PCs and gives big savings on disk space. More
than half of SLIM Ver 1.00 and 1.01 users who responded to a
questionnaire said that SLIM allowed them to postpone or cancel a
hard disk upgrade.

A report facility shows which of a group of files are compressed,
by how much and with what total savings.

SLIM's compact size (less than 24KB) makes it practical for
floppy as well as hard disk machines.

The RAM resident part of SLIM uses 73KB of main memory.

System Requirements: IBM PC or MSDOS machine, MSDOS Ver 2.00+,
256K+ RAM
S L I M U s e r M a n u a l Pg 5


2.0 G E T T I N G S T A R T E D

This is for people who want to get on with using SLIM and read
about it later. If you are new to SLIM, read on. If you are
upgrading from an older version of SLIM, go to section 2.2.

2.1 NEW USERS OF SLIM
_________________

To get SLIM up and running, you need only one file, SLIM.EXE.
This contains all the functions of a working system. Copy
SLIM.EXE your hard disk. The root directory is recommended.

If you do not have a hard disk, copy SLIM.EXE onto any system
(boot) disks you will use to boot your machine before accessing
compressed files. It is not necessary to have SLIM.EXE on all
disks with compressed files, if you only need to read the files.

If your system disk has a file AUTOEXEC.BAT, add a line to the
file, with the text : "SLIM ON". This ensures that every time
your computer is powered on, compressed files can be accessed
normally. If you do not have a file AUTOEXEC.BAT, create one with
the same line.

C>TYPE AUTOEXEC.BAT
SLIM ON
C>

Re-boot your system (Ctrl-Alt-Del). The following message will
appear when AUTOEXEC.BAT runs.

C>SLIM ON
S L I M F i l e C o m p r e s s i o n S y s t e m V1.10

Copyright (C) 1988,1991 Dominic Herity.

Loading SLIM de-compressor
C>

This indicates that the RAM resident part of SLIM is now loaded.
This is needed to allow you to access compressed files. It is
also needed to de-compress compressed files (see section 5). As
SLIM now occupies 72KB of RAM which was previously available for
programs, some larger programs may not run with SLIM loaded. This
is more of a problem with systems containing 256K RAM, but if
your machine has 512K or more, you should have no difficulty.
Watch out for applications reporting "insufficient memory",
"program too big to fit in memory" or not running after SLIM is
loaded. Lack of RAM is the most likely cause of such a failure.

Now your system is ready to handle compressed files. All you have
to do now is compress some, and start saving disk space (or
expanding your disk, if you prefer to see it that way).
S L I M U s e r M a n u a l Pg 6


Pick one or more files for compression. As this is a
familiarization exercise, take a small one (say, between 5000 and
30000 bytes), since compressing large files takes a lot of time.
The file selected should also be one that you read often, but
write to seldom or never. An EXE or COM file is a good candidate
on this basis, but these don't compress as well as text or
program source code. Spreadsheets and database files compress
best, but they tend to be too large for our present purposes.
DON'T select a file that you need before SLIM is turned on, e.g.
COMMAND.COM or SLIM.EXE, as SLIM will refuse to compress these.
(See section 3 for more details.) Also, ensure that you have at
least as many bytes free on your disk as the file you wish to
compress, because SLIM needs workspace to compress a file.

Let's assume you chose to compress the DOS utility program
FIND.EXE. (I suggest this because it gives unusually good results,
at least in PC-DOS Version 3.00.) Type :

C>SLIM FIND.EXE

SLIM displays a byte counter when compressing the file and
reports the saving when it is finished.

C>SLIM FIND.EXE

S L I M F i l e C o m p r e s s i o n S y s t e m V1.10

Copyright (C) 1988,1991 Dominic Herity.

Original Compressed Save
Bytes Bytes (%) File (Press any key to abort)

6363 1019 83% C:FIND.EXE

6363 bytes reduced to 1019 in 1 files saving 5344 (83%)

360448 bytes free out of 20971520. SLIM is RESIDENT and ACTIVE.
C>

In the unlikely event that SLIM cannot compress the file, pick
another one. Most files are compressible.

So you have liberated some disk space from FIND.EXE. Now try to
use the compressed file.

C>FIND "SLIM" SLIM ON
C>

As you can see, FIND.EXE works just as before. SLIM works on all
sorts of files just as easily, word processor documents,
spreadsheets, ASCII files, and peculiar unique files used by
various software packages.
S L I M U s e r M a n u a l Pg 7


To see if a file or set of files is compressed, and by how much,
use the SLIM R command. For example :


C>SLIM R DOS\*.*

S L I M F i l e C o m p r e s s i o n S y s t e m V1.10

Copyright (C) 1988,1991 Dominic Herity.

Original Compressed Save
Bytes Bytes (%) File (Press any key to abort)

6363 1019 83% DOS\FIND.EXE
8544 4044 52% DOS\SHARE.EXE
15123 9882 34% DOS\ATTRIB.EXE
3629 2539 30% DOS\SYS.COM

33659 bytes reduced to 17484 in 4 files saving 16175 (48%)

96256 bytes free out of 20971520. SLIM is RESIDENT and ACTIVE.
C>

But before you get carried away, glance through the rest of this
manual. You could read it while SLIM crunches up some of those
monstrous files that have been hogging your disk.

2.2 UPGRADING FROM AN EARLIER VERSION OF SLIM
_________________________________________

SLIM V1.10 behaves pretty much the same as versions 1.00 and
1.01. It just does it faster and better. Files compressed with
the earlier versions can be used the same as before. However,
SLIM V1.10 compresses somewhat better than its predecessors, so
you might find it worthwhile to expand and re-compress the old
files. See Section 9 for more information on changes.

All copies of your earlier version of SLIM should be removed from
where they might be used inadvertently. If you have stray extra
copies of SLIM.EXE lying around, now would be a good time to get
rid of them. The main reason for this is to avoid one version of
SLIM being loaded and another being used afterwards. If two
versions of SLIM from V1.10 on are mixed in this way, SLIM
outputs an error message and refuses to work. The message reads
"A different version of SLIM has been loaded. Use one only".

Removal of old versions is particularly important for versions
1.00 and 1.01. This is because the method of communicating with a
previously loaded RAM resident part (loaded by 'SLIM ON') has
been changed in Version 1.10. So, for example, a V1.00 RAM
resident part will not realize that SLIM V1.10 is 'family' and
will expand files when an access is attempted. This would make
SLIM V1.10 take compressed files to be uncompressed. So confusion
results.

See Section 4 for more information on the function and behavior
of the RAM resident part of SLIM.
S L I M U s e r M a n u a l Pg 8


3.0 C O M P R E S S I N G F I L E S


3.1 BASIC OPERATION
_______________

Before files can be compressed, SLIM must have been loaded by the
SLIM ON command. This is because the compression process performs
a check using the RAM resident de-compressor, to guard against
internal bugs which might prevent later access to a compressed
file.

Files can be compressed by entering :

C>SLIM [n] filespec

where 'filespec' is a filename including optional path. More than
one file can be compressed if wildcards ('*' or '?') are included
in the filespec. SLIM will take each file matching the filespec
and attempt to compress it. '[n]' is an optional number 0 to 9
which alters the 'thoroughness' of the attempt to compress the
file(s). This will not normally be used, but see section 3.3
below for more information.

As SLIM compresses each file, it displays a byte count indicating
the progress of compression. If you want SLIM to skip a file,
press any key and SLIM will abandon the file on the next counter
update and proceed to the next file.

When a file has been compressed, the original and compressed
sizes are displayed on screen, as in the SLIM R command.

If SLIM encounters a file which is already compressed, it will
bypass it.

When all files have been processed, SLIM displays a summary of
bytes saved and total bytes and bytes free on the disk. See
example below.

C>SLIM DOS\*.*

S L I M F i l e C o m p r e s s i o n S y s t e m V1.10

Copyright (C) 1988,1991 Dominic Herity.

Original Compressed Save
Bytes Bytes (%) File (Press any key to abort)

6363 1019 83% DOS\FIND.EXE
8544 4044 52% DOS\SHARE.EXE
15123 9882 34% DOS\ATTRIB.EXE
3629 2539 30% DOS\SYS.COM

33659 bytes reduced to 17484 in 4 files saving 16175 (48%)

96256 bytes free out of 20971520. SLIM is RESIDENT and ACTIVE.
C>
S L I M U s e r M a n u a l Pg 9


3.2 DISK SPACE REQUIRED
___________________

SLIM needs some workspace on disk to compress files. When
compressing, it reads the original file and produces the
compressed file, before deleting the original. To do this, SLIM
needs up to as much free disk space as the largest file to be
compressed. If SLIM runs out of disk space while compressing a
file, it will output an error message, leave the file
uncompressed and proceed to the next file. If you are short of
free disk space and wish to compress a number of files, some
small and some large, compressing the small files first may free
enough disk space to allow the large files to be compressed.

3.3 COMPRESSION THOROUGHNESS
________________________

When compressing files, SLIM can be instructed to 'try harder' or
'hurry up' by specifying a compression thoroughness parameter.
This is done by inserting a number between 0 and 9 before the
filespec. For example :

C>SLIM 7 *.EXE

will compress all .EXE files in the current directory with a
thoroughness parameter of 7. The parameter defaults to 5 if not
specified. A higher value means a longer runtime and (possibly)
better compression performance. A lower value means shorter
runtime and (possibly) worse compression. These results are not
guaranteed, however, and it may happen that a file compressed
with a parameter of 6 is actually larger than one compressed with
a parameter of 5. In addition for larger parameter values,
runtime tends to double for each increment in parameter value,
with little or no improvement in compression. For these reasons,
it is usually best to leave this parameter alone. It should be
reserved for when you badly need better compression on a
particular file, or use a low value to quickly squash a few files
to give you some temporary disk space.

3.4 INCOMPRESSIBLE FILES
____________________

Occasionally, SLIM will encounter a file whose 'compressed'
size is actually larger than the original. When this happens,
SLIM leaves the file uncompressed and outputs a message saying
that it cannot compress the file.

3.5 RUNTIME
_______

File compression take a long time compared to the small delay on
access. Fortunately, compression is an infrequent task and only
needs to be repeated when new files are added to the disk or when
files have been written to. Files which are frequently written to
should not be compressed. The short term gain of disk space is
outweighed by the time taken to re-compress the file and the
inconvenience of running compression often.
S L I M U s e r M a n u a l Pg 10



Large quantities of files can be compressed overnight using a
batch file. If the batch file is still running when you need the
machine again, it can be safely interrupted by pressing Ctrl-
Break. The batch file can be re-started later and SLIM will
quickly skip over files already compressed. Here are some example
batch files for compressing large numbers of files.

C>TYPE SLIM1.BAT
REM COMPRESS ALL FILES IN WS DIRECTORY
C:\SLIM C:\WS\*.*
C>
C>TYPE SLIM2.BAT
REM COMPRESS ALL FILES IN :
REM WS, WS\DATA, SYMPH, SYMPH\DATA, DBASE, DOS ETC.
C:\SLIM \WS\*.*
C:\SLIM \WS\DATA\*.*
C:\SLIM \SYMPH\*.*
C:\SLIM \SYMPH\DATA\*.*
C:\SLIM \WS\*.*
C:\SLIM \DBASE\*.*
C:\SLIM \DOS\*.*
C:\SLIM \XTREE\*.*
C>
C>TYPE SLIM3.BAT
REM COMPRESS ALL FILES IN :
REM WS, WS\DATA, SYMPH, SYMPH\DATA, ETC.
FOR %%X IN ( WS WS\DATA SYMPH ) DO C:\SLIM \%%X\*.*
FOR %%X IN ( SYMPH\DATA DBASE DOS XTREE ) DO C:\SLIM \%%X\*.*
C>

The last of these examples is the most useful. By customizing
SLIM3.BAT to your own machine's directory structure, you can
compress all the files in some or all of your directories. The
batch file can be re-run at intervals to catch any new or
rewritten files. When you change your directory structure, edit
the batch file accordingly.

3.6 FORBIDDEN FILES
_______________

Compressed files can only be correctly read when SLIM is
activated, using the SLIM ON command. This command would
typically be in the AUTOEXEC.BAT file. But certain files must be
read on power up, before SLIM is activated. Examples are
COMMAND.COM, CONFIG.SYS and of course, SLIM.EXE. If any of these
files were compressed, the computer could not power up properly.
To prevent this, SLIM refuses to compress any files with a ".SYS"
extension and any files called COMMAND.COM, IBMBIO.COM,
IBMDOS.COM, AUTOEXEC.BAT or SLIM.EXE. If SLIM encounters any of
these files during compression, it outputs a message saying the
file should not be compressed.
S L I M U s e r M a n u a l Pg 11


4.0 A C C E S S I N G C O M P R E S S E D F I L E S


4.1 CONFIGURING YOUR SYSTEM WITH SLIM
_________________________________

To ensure access to compressed files, enter the command 'SLIM ON'
in your AUTOEXEC.BAT file. Make sure that this command occurs
before any commands that access compressed files. For example, if
you compress SK.COM, and you have the command SK in AUTOEXEC.BAT,
you must place the 'SLIM ON' command before the 'SK' command.

If you do not wish to have SLIM permanently loaded, which may be
the case if you have an application that needs lots of memory,
make sure to enter the SLIM ON command before attempting access
to any compressed files. Once SLIM is loaded into memory by the
SLIM ON command, it cannot be removed, except by restarting the
computer (Ctrl-Alt-Del).

4.2 HOW COMPRESSED FILES ARE ACCESSED
_________________________________

Once loaded, SLIM gives automatic access on demand to compressed
files. It does this by intercepting any calls a program
(including COMMAND.COM) makes to DOS. Normally, SLIM passes these
calls straight on to DOS, but when a call is detected which opens
a compressed file, SLIM reads the file and makes a full size copy
on disk for the program to use. It then changes the name of the
compressed file to a name it recognizes itself and renames the
new full size file to the original file name. Only then does it
pass the call on to DOS. Neither DOS nor the program know that
this is happening, so operation is completely automatic. When an

expanded file is closed without being modified, SLIM (equally
quietly) deletes the expanded copy and renames the original
compressed file to its original name. If a program modifies an
expanded copy of a file, SLIM deletes the compressed original and
leaves the expanded new file on disk.

Compressed files may be renamed without affecting access.
Compressed files can also be deleted. If a compressed file is
copied to another file with SLIM ON, the new file will be a full
size, not a compressed, copy of the original.

4.3 COPYING AND BACKING UP COMPRESSED FILES
_______________________________________

In some circumstances, you may wish to manipulate files without
expanding them. Copying and backing up files are such
circumstances. The command SLIM OFF is provided for this reason.
It prevents SLIM from expanding files when opened, but does not
remove SLIM from memory or prevent it expanding a COM or EXE file
when it is run.
S L I M U s e r M a n u a l Pg 12


Do not forget to turn SLIM ON again when the copying or backup is
complete. If in doubt, an extra SLIM ON command will not hurt. To
see if SLIM is ON or OFF enter the command SLIM and the status
will displayed, INACTIVE meaning OFF and ACTIVE meaning ON.

If you mistakenly access a file with SLIM OFF or not loaded, the
file will not make sense, but the error will be obvious. Most
programs report in a fairly civilized manner when a file is not
what they expect. If the compressed file is accessed as an ASCII
or text file, the file will seem to contain the message '= sLiM'
and nothing else. If a program in a compressed COM file is
mistakenly run without SLIM loaded, the program will stop
immediately.

4.4 DISK SPACE
__________

Because SLIM makes a full size copy of each file that is
accessed, there must be enough disk space free to accommodate all
the full size copies that will be need at any one time. This does
not, however, include full size copies of COM or EXE files that
are being run, as these are deleted immediately when their
contents are loaded into memory.

This can be illustrated by the following example.

C>SLIM R *.*

S L I M F i l e C o m p r e s s i o n S y s t e m V1.10

Copyright (C) 1988,1991 Dominic Herity.

Original Compressed Save
Bytes Bytes (%) File

46080 39720 13% WSOVLY1.OVR
25600 19563 23% WS.COM
32256 18004 44% WSMSGS.OVR
19840 8473 57% DOCUMENT.TXT

123776 bytes reduced to 85760 in 4 files saving 38016 (30%)

106596 bytes free out of 20971520. SLIM is RESIDENT and ACTIVE.
C>

I will run WS.COM (a well known word processor) to edit the file
DOCUMENT.TXT. The files WS.COM, WSOVLY1.OVR and WSMSGS.OVR are
compressed, as is DOCUMENT.TXT. WS.COM uses data in WSOVLY1.OVR
and WSMSGS.OVR, so it accesses these. So my disk must have at
least 46080 + 32256 + 19840 = 98176 bytes free. (More accurately,
it must have 48K + 32K + 20K = 100K bytes free, since data is
stored on the disk in units no smaller then 2K.) I don't need
25600 bytes for WS.COM as this is only expanded transiently,
until loaded into memory. But I do need to have 25600 bytes free
just to run WS.COM.
S L I M U s e r M a n u a l Pg 13


Don't panic! You do NOT need a calculator to use SLIM. The above
information is provided so that you will know (a) what is
happening, if it happens, and (b) what must be done to stop it
happening. If you prefer, do what you did last time you ran out
of disk space - start deleting files.

When SLIM runs out of disk space on expansion, it returns an
'Access denied' error as a response to the DOS call, but the
message on screen may not make this obvious. For example, if you
try to execute a compressed .EXE file, and SLIM fails to expand
it, the message that appears on screen is 'Bad command or file
name'.

SLIM will also be unable to expand a file if the file is in the
root directory of a disk and the root directory is full. A little
known peculiarity of DOS is that the root directory of a disk
(for example A:\) can store only a limited number of directory
entries (filenames). The limit is normally 112 for a 360K floppy
disk and 512 for a hard disk. Since the volume label occupies one
directory entry, the practical limit is 111 and 511 respectively.
Sometimes people find this out the hard way when they try for
example to copy 200 1K files onto a floppy disk.
If a compressed file is in a full root directory, SLIM will fail
to produce an expanded copy. To check if this is the cause of
failure, try copying files (with SLIM turned OFF) and if this
fails even though enough disk space is free, a full directory is
the probable cause. A remedy to a full root directory is to copy
all or some files into a sub-directory (after freeing enough
space to create the sub-directory). Even if you do not need the
files to be compressed, a nearly full root directory is likely to
cause further trouble.

Do not put a write protect tab on a floppy disk if you want to
access compressed files on that disk, as this prevents generation
of an expanded copy. This is not a problem, however, if you only
use the disk for file storage. The file may be copied from the
write protected disk with SLIM turned OFF, and then accessed on
an unprotected disk, with SLIM turned ON.

4.5 TRANSPARENCY FAILURES
_________________________

SLIM gives programs the illusion that small files are big files.
It does this very successfully and almost all of the software is
fooled all of the time. But there are some cases where the
illusion cannot be maintained and compression must be either
avoided or done carefully.

The first case is where a program obtains the size of a file from
its directory entry and then reads that number of bytes when it
opens the file. The intention is to read the whole file, but if
the file is compressed, only the number of bytes that the
compressed file occupies are read. This behavior has been seen
with the DOS XCOPY command (Ver 3.21 at least) and PKZIP (Ver
1.01 at least) from PKWARE.

A solution is to change the name of the offending program and
S L I M U s e r M a n u a l Pg 14


replace it with a batch file that turns SLIM off, runs the
program, and turns SLIM on again. For example :

C>TYPE XCOPY.BAT
REM
REM XCOPY WITH SLIM OFF.
REM PREVENTS TRUNCATION AND PRESERVES COMPRESSION.
REM
SLIM OFF
OLDXCOPY %1 %2 %3 %4 %5 %6 %7 %8 %9
SLIM ON
C>

The second case where SLIM confuses other software is a
particular copy protection method. The method bypasses DOS to
read the disk area in which the program is presumed to be stored,
to check it is still there. The details of where this is on the
user's disk is written into the program by an installation
program. If an ordinary copy of the program is run, it will see
that its own code is not in the expected place on disk. It then
'knows' that an unauthorized copy is being used. Variations on
this theme use other files apart from the program file or check
the file allocation table instead of the data area of the disk.
Programs copy protected by these means tend to have warnings in
the documentation against copying the program file or files.

When SLIM compresses a file, it reads the original, writes a new
file on a different area of disk and deletes the original. This
causes the copy protection method to be activated.

The obvious remedy here is to not compress files subject to such
a copy protection scheme. If you must compress such files, it may
be possible to get an unprotected copy of the software from the
vendor. Since copy protection has become unpopular, it is not
likely that this problem will happen with any new software you
acquire.
S L I M U s e r M a n u a l Pg 15


5.0 D E - C O M P R E S S I N G F I L E S


5.1 BASIC OPERATION
_______________

The SLIM X (eXpand) command de-compresses a file or set of files.
This command can only be used if SLIM has been made RAM resident
with the SLIM ON command. Example :

C>SLIM X DOCUMENT.TXT

S L I M F i l e C o m p r e s s i o n S y s t e m V1.10

Copyright (C) 1988,1991 Dominic Herity.

Original Compressed Save
Bytes Bytes (%) File

19840 8473 57% DOCUMENT.TXT

19840 bytes were reduced to 8473 in 1 files saving 11367 (57%)

83968 bytes free out of 20971520. SLIM is RESIDENT and INACTIVE.
C>

5.2 DISK SPACE REQUIRED
___________________

For SLIM X to execute correctly, enough free disk space must be
available to store an expanded file as well as the compressed
file, because the compressed file is only deleted after the de-
compressed file is produced.
S L I M U s e r M a n u a l Pg 16


6.0 T E C H N I C A L I N F O R M A T I O N


6.1 FILES USED BY SLIM
__________________

Using SLIM, you will occasionally glimpse files with strange
names lurking on your disk. SLIM uses files called
'SLIMnnnn.$$$' where nnnn is a four digit decimal number. The
other files are the compressed originals of open files (See
Section 4.2). These will be seen if, for example, you call up a
directory display in a word processor whose working files are
compressed.

If you see any files of the type 'SLIMnnnn.$$$' when you are SURE
that you do not have any compressed files open (for example, on
power up), this indicates power loss or other failure when the
file was being accessed. Rename the file to something else (e.g.
WHATISIT.FOR) and use the SLIM R command to see the original file
size. If that size is the same as that of another file in the
same directory, then WHATISIT.FOR is probably the compressed
original of that file. If you are sure that WHATISIT.FOR is not
an older version of a revised file, rename it to the filename of
your choice and continue to use it. Otherwise, delete it.

6.2 RAM RESIDENT INTERFACE
______________________

When SLIM is loaded, the RAM resident part is kept in memory. It
is necessary for the non-resident part to communicate with it for
a number of reasons. One reason is to turn it on and off. Another
is to verify (after compressing a file) that a file can be
accessed. This is a safety measure to protect against a bug in
SLIM, which virtually guarantees that SLIM will never cause loss
of data. A third reason is to use the RAM resident part to expand
a compressed file (X command).

The interface to SLIM's RAM resident part supports the
TesSeRact(TM) Standard for Ram-Resident Program Communication.
For information about TesSeRact, contact the TesSeRact
Development Team at:

TesSeRact Development Team
c/o Chip Rabinowitz
2084 Woodlawn Avenue
Glenside, PA 19038
1-215-884-3373

Compuserve: 70731,20
MCIMAIL: 315-5415

This MCIMAIL Account has been provided to the TesSeRact
Development Team by Borland International, Inc. The TesSeRact
Development Team is in no way associated with Borland
International, Inc. TesSeRact is a trademark of the TesSeRact
Development Team.
S L I M U s e r M a n u a l Pg 17


7.0 E R R O R A N D O T H E R M E S S A G E S


There follows an alphabetically sorted list of error messages
produced by SLIM, with (as appropriate) some information on
probable cause and references to this manual for further
information.

MESSAGE : A different version of SLIM has been loaded.
CONTEXT : At startup
CAUSE : Two versions (at least) of SLIM.EXE are present. One
was loaded earlier (SLIM ON) and the other has been
run.
FURTHER INFORMATION : Section 2.2


MESSAGE : aborted
CONTEXT : After failed compression of a file
CAUSE : User hit a key, abandoning compression
FURTHER INFORMATION : Section 3.1

MESSAGE : Can't compress this file
CONTEXT : After failed compression of a file
CAUSE : File size can't be reduced
FURTHER INFORMATION : Section 3.4

MESSAGE : Can't expand this file
CONTEXT : Failed expansion of compressed file
CAUSE : Not enough free disk space to make expanded copy.
FURTHER INFORMATION : 5.2

MESSAGE : Can't open (filename)
CONTEXT : During compression, expansion or reporting
CAUSE : File was found but could not be opened.
FURTHER INFORMATION :

MESSAGE : Can't open new file
CONTEXT : At start of file compression
CAUSE : Full disk or directory
FURTHER INFORMATION : Section 3.2

MESSAGE : Can't write to output file
CONTEXT : During file compression
CAUSE : Disk full
FURTHER INFORMATION : Section 3.2

MESSAGE : Insufficient Memory
CONTEXT : At SLIM startup
CAUSE : Not enough memory available for SLIM to run
FURTHER INFORMATION : Section 1

MESSAGE : Internal Error : Can't compress this file
CONTEXT : At end of file compression
CAUSE : SLIM internal error. Should not occur
FURTHER INFORMATION : Section 8 - Please contact the author
S L I M U s e r M a n u a l Pg 18


MESSAGE : Loading SLIM de-compressor
FURTHER INFORMATION : Section 4.1

MESSAGE : No files
CONTEXT : At SLIM startup, compressing, expanding
or reporting on files.
CAUSE : No files were specified for processing.
FURTHER INFORMATION : Section 2.0, 3.1, 5.1

MESSAGE : Should not compress this file
CONTEXT : At start of file compression.
CAUSE : SLIM refuses to compress file.
FURTHER INFORMATION : Section 3.6

MESSAGE : SLIM de-compressor already off
FURTHER INFORMATION : Section 4.3

MESSAGE : SLIM de-compressor already on
FURTHER INFORMATION : Section 3.1, 4.3

MESSAGE : SLIM de-compressor not loaded
FURTHER INFORMATION : Section 4.3

MESSAGE : SLIM de-compressor turned off
FURTHER INFORMATION : Section 4.3

MESSAGE : SLIM de-compressor turned on
FURTHER INFORMATION : Section 3.1, 4.3

MESSAGE : SLIM must be loaded to do compression or expansion.
CONTEXT : Attempt to expand or compress files.
CAUSE : For these commands to be used, it is necessary for
SLIM to be RAM resident first. (SLIM ON command.)
FURTHER INFORMATION : Sections 3.1, 5.1

MESSAGE : PC-DOS or MS-DOS Version 2.00 or greater required
CONTEXT : SLIM startup.
CAUSE : You are using an old version of DOS (Ver1.xx).
FURTHER INFORMATION : Section 1

MESSAGE : Write error on output
CONTEXT : After file compression.
CAUSE : Disk full.
FURTHER INFORMATION : Section 3.1
S L I M U s e r M a n u a l Pg 19


8.0 T E C H N I C A L S U P P O R T


8.1 SUPPORT POLICY
______________

I have good reason to believe that my software is more reliable
than most in the computer industry, and I intend to keep it that
way. If you have a problem with SLIM, that means that either
there is a bug in the software or the manual is misleading. In
either case, I want to know about it. I gladly offer a free
upgrade of SLIM to any registered user for a usable bug report
(whether it was reported previously or not).

If you don't have a problem, but have suggestions or comments,
I'd like to see them.

8.2 WHAT TO SEND
____________

If you are reporting some abnormal behavior by SLIM, I will
probably need to see it to be of any help. The more complete the
information you provide, the quicker and more helpful my response
can be. Ideally, you should send a floppy disk with a README file
containing your explanation of the problem. It should also
include copies of all files involved. If I can see a bug, I'm
most of the way to fixing it. I undertake to use any files
received in this way for debugging only and to destroy all copies
when that is done.

Please make sure the problem still happens when you boot your
system without an AUTOEXEC.BAT or CONFIG.SYS file. If you can
make it happen using only the files on the floppy disk you are
sending, and not your hard disk, then it is fairly sure that I
can reproduce the problem.

It is usually easier to include a batch file than to explain what
to type. Please mention what DOS version you use (MSDOS or PCDOS
with numbers), your machine (manufacturer, CPU type, RAM. etc.),
and anything else you think may be relevant.
S L I M U s e r M a n u a l Pg 20


9.0 V E R S I O N H I S T O R Y


Version : 1.00 Released : November 1988

This is the initial release of SLIM.


Version : 1.01 Released : April 1989

The shareware version previously demonstrated compressibility of
files larger than 64K. Since this can be time-consuming, large
files are now skipped over. Licensed version behaves as before.


Version : 1.10 Released : February 1991

Compression is typically many times faster for large files (over
64KB approx.).
Expansion is at least 50% faster for large files. Bigger savings
for small files.
Compression is improved significantly. Users of earlier versions
should re-compress their files when convenient.
Work space on disk used when compressing files reduced to half.
SLIM.EXE is reduced from over 30KB to less than 22KB.
Shareware edition of SLIM now compresses files of unlimited size.
Various bugs fixed.
S L I M U s e r M a n u a l Pg 21


10.0 R E G I S T R A T I O N


10.1 THE PITCH
_________

Registration of SLIM will entitle you to :

* A licensed copy of the version current at registration time

* A printed manual for same

* Application support from the author

* Notification of future upgrades

* The chance to order these upgrades at a large discount

* Free upgrade if released within 3 months of registration

If you believe that SLIM enhances your computer, or if you want
the latest update, or if you would like first refusal of future
enhancements at a special price, please register now. The next
page contains an order form and optional questionnaire which you
should print out, fill in and mail to me. You can also order via
e-mail on CompuServe or Internet, with a credit card.

SLIM registration costs 45 US dollars per machine with no funny
business. That means that disk, manual and shipping worldwide by
airmail are included in the price.

I rely on your support.

Inquiries about site licenses are welcome. If you are a software
developer worrying about the size of files your application uses,
SLIM could save your time, your money and your sanity.
S L I M U s e r M a n u a l Pg 22


10.2 SLIM ORDER FORM
_______________

(PLEASE USE BLOCK CAPITALS)

Title (Mr/Ms) : ____

Surname : __________________

Personal Name : __________________

Company : __________________
(if license for company, rather than personal use.)

Address : _________________________________________

_________________________________________

_________________________________________

_________________________________________

_________________________________________


Number of licensed copies of SLIM required at $45.00 each : ____

Disk (please tick one, 5.25" by default) : 5.25" ____ 3.5" ____

Method of payment (please tick one) :

Access/EuroCard/Mastercard/Visa ____ American Express ____

Cheque (your country's currency) ____ Bank Draft (US$) ____

If payment by credit card, please supply following information :

Card number ____________________ Expiry Date ______________

Signature (if order on paper) ______________________________

Charge per copy is 45 U.S. dollars or equivalent, including
registration, printed manual, postage and packing.

If payment is by cheque in your country's currency, please ensure
that payment is sufficient and allow for exchange rate variation.

Please do NOT send a eurocheque for U.S. dollars OR a U.S. dollar
cheque drawn on a non-U.S. bank.

This order may be mailed to :
Mr Dominic Herity, PO Box 3038, Dublin 4, Ireland.

Electronic credit card orders may be sent to :
CompuServe 100016,3477 or internet [email protected]

Thank you. Please see questionnaire on following pages.
S L I M U s e r M a n u a l Pg 23


10.3 QUESTIONNAIRE
_____________

This questionnaire is entirely optional. You may ignore it or
fill it in partially or fully and return it with your order. But
I would be obliged if you would take a few minutes over it to
help me improve SLIM to meet your needs better.

10.3.1 YOU
What is your profession ? ___________________

How often do you use your computer ? (Please tick one)

Occasionally____ Daily____ Much of time____

10.3.2 YOUR COMPUTER
Manufacturer ___________________ Model ___________________
CPU (Circle one) 8088 8086 80286 80386 V20 V30

Other (please specify) ___________________

Speed(MHz) ___________________ RAM(KB) ___________________

Hard Disk Capacity (MB) ___________________

Floppy drives : Number ____ Capacity (KB) ____
Form Factor (Circle one) 5.25" 3.5"

10.3.3 YOUR APPLICATION
What do you mainly use your computer for ?
(Circle one or more) Word processing Spreadsheets CAD
Database Accounts Software Dev't Desktop Publishing
Games Other (please specify) ___________________

List the software packages that you use most often

1 ___________________ 4 ___________________

2 ___________________ 5 ___________________

3 ___________________ 6 ___________________

10.3.4 YOUR USE OF SLIM
How did you acquire your shareware copy of SLIM ?
e.g. friend, shareware company (please specify)

___________________

Approximately how much disk space do you expect to save ?

___________________bytes reduced to ___________________

What types of files do you expect to make the savings on ?
(Circle one or more) Word processor ASCII text
EXE and COM files Database Spreadsheets Graphics

Other (please specify) ___________________
S L I M U s e r M a n u a l Pg 24


Approximately what range of file sizes do you wish to
compress ?
From ___________________ to ___________________ bytes

Please rank these potential improvements for SLIM in your
order of choice

__ Faster compression

__ Faster expansion/access

__ Automatic re-compression of files written to

__ More compression/smaller compressed files

__ Less disk workspace used by SLIM when compressed
files are being accessed.

__ Other (please specify) ___________________

__ Other (please specify) ___________________

How do you rate this manual (Circle one)
Very Bad Bad Fair Good Excellent

Please Indicate any parts of this manual which are unclear
or difficult :

__________________________________________________________

Has SLIM enabled you to postpone or cancel upgrading your
hard disk ? (Circle one) Yes No

Please list any other file compression utilities you know,
whether you have used them, and any comments you have on
them.

__________________________________________________________

__________________________________________________________

__________________________________________________________


10.3.5 YOUR COMMENTS
Any suggestions for product improvement, complaints about
shortcomings, etc. would be much appreciated, however
small you may consider them. Attach a separate sheet if
necessary.

__________________________________________________________

__________________________________________________________

__________________________________________________________
_____________________________


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