Archiving - A Weeny Introduction By Someone Who Hasn't The
  Foggiest What He Is Talking About (hold your wicked remarks!)

                        By James Judge

Aaaaargh, another article that nicely fits into my 'techie'
section. So far it seems as if there is only me and Piotr who
gives a damn about computers and how they run - c'mon, share your
knowledge on anything from installing a disk drive (BMK, we're
waiting) and aspects of other computers. So far it has been ST, ST
and ST. I know there is a large PC group out there and that IS the
most technical computer us home users are ever likely to get our
mitts on!

OK, what's on today's menu? (he asks as he picks yesterday's
dinner out of his teeth) Well, in computer jargon we are looking
at archiving data, or in layman's jargon - making files a teensy
bit smaller.  At one time or another we have all come across this
form of data compression, whether we knew it or not. The most
common form will be on BBSs and cover disks. If you've ever
dabbled in either of those you'll have definitely come across a
small program that fits snugly into a few K and when you run it,
explodes into a whopping megabytes worth of data. This is the
obvious data compression.  More on it later.

The other type just runs in the background. If you've ever used an
early STF coverdisk, you'll have noticed that while the program on
the disk loads a load of small dots may appear around the border.
This is a packer at work. When the main program is run it goes
looking for its usual data files etc. and instead of them being
the normal length they will have been put through a program that
squishes it into something that is runnable, but needs a brief
moment to be expanded in memory. The expansion is the little dots.

So, you now know what to look for, but how do YOU do it? Well, the
first step is crack out the old PD catalogue and look for
archivers and packers. If you own an ST you can spend out œ2.50
and get a disk with a few packers from SynTax that I will be
sending to Sue with this article (unless she doesn't accept
it...). If not you're on your own.

Once you've got your program you're ready to roll. The program I
use is called Zip and it is widely used with STs and has got a
brother on the PC, PKZip or summat.

When you have got your program loaded you will need to tell it
what to do. Depending on the program you will need to tell it
certain things, but with Zip all I have to do is select some
files, click on the go button and then check the compression.

Let me explain that. What you tell the standard archiver is what
files you want to be compressed into either a small data file to
be unarced by the program at a later date (useful for BBS) or a
runnable program that will, if given enough disk space, unarc
into the original files.  I only understand the basics as to how
the compression works so I'll try and put it into English.

When a programmer programs an archiver, he tells the program to
firstly look at the file(s) selected and then dissect it into small
pieces. The way it does the dissection is dependent on the program.
It then puts the bits and pieces back together, but in a different
way, leaving out certain bits that can be re-constructed while it
is being de-arced. Also the program could take out useless parts
of the code that is still readable eg:

For those of us who have got 1st Word we have probably noticed
that if we save in the ASCII document style there are spaces where
we put it when you read it from the desktop. In other words it
looks like what you are now reading.

If we save in the 1st Word style and then try to read the document
from the desktop...

...itcomesoutlikethis,doesn'tit.Itlooksconfusing,butthisisbasically
whatanarchiverdoes...

...take all the spaces from the code, reducing the overall file
size.  It does, of course, do mind numbing calculations to remove
all the unwanted data or dissect it and re-assemble in a different
way, but that is really all there is to it. The computer takes
away the spaces!  How successful the archiver is, depends on your
archiver. This Zip program that I use does quite well, I think.
Take a 300K AGT game (all the runner programs and data files
together). Zip is able to take that, juggle around with it, and
then belch out a program that will self extract (de-archive) that
is only 70K in length, a great help.

Once you've got your archiver sussed you can then start to send,
say, five terrible AGT games to your worse enemy per disk, instead
of two. It is also a useful way of keeping those games you've
played, but don't want to throw. Just archive them and store four
or five on a disk instead of four or five on four or five disks.

Well, I think I've taken you through the preliminaries involved
with archiving, why don't you try it?